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Term Definition/Description Source
T.120 A family of ITU-T international standards for audio-embedded document conferencing, data collaboration and audiographic conferencing. Multimedia
table An ordinary arrangement of data, especially one in which the data is arranged in columns and row in a rectangular form. ISO/TC 211
table of meridional parts A table listing lengths of the meridian from the Equator to the various parallels of latitude increased in the proportion required to show lengths along the parallels equal to the corresponding length along the Equator. HDBK-850
tabular data Data in row and column format. See also relational data base. HDBK-850
tachymeter (tacheometer or tachometer) A surveying instrument designed for use in the rapid determination of distance, direction, and difference of elevation from a single observation. There are several forms of these instruments that may be classed as tachymeters: (1) An instrument in which the base line for distance determination is an integral part of the instrument. The term tachymeter is usually applied to this group. (2) An instrument equipped with stadia wires or gradienter, the base for distance determination being a graduated rod held at the distant point. See also autoreducing tachymeter. HDBK-850
tachymetry (tachometry) A surveying method used to quickly determine distance, direction, and relative elevation of a point with respect to the instrument station by a single observation. An example of tachymetry in the United States (where the term is less familiar) is the stadia method. HDBK-850
Tactical Air Operations Center (TAOC) Another critical node in the Marine Corps tactical air command and control system; a subordinate agency of the TACC, its: principal concern is defensive AAW. The TAOC controls an air defense sector, en route air traffic and air defense operations with manned interceptors and surface to air missiles. USIS 95
tactical air reconnaissance The use of air vehicles to obtain information concerning terrain, weather, and the disposition, composition, movement, installations, lines of communications, electronic and communication emissions of enemy forces. Also included are artillery and naval gunfire adjustment, and systematic and random observation of ground battle areas, targets, and/or sectors of airspace. USIS 95
Tactical Air Reconnaissance Pod System (TARPS) An interchangeable sensor package flown on carrier-based F-14s. Sensors include day-only optical imaging and day/night infrared. USIS 95
Tactical Aircraft Mission Planning System (TAMPS) Mission planning system used by the U.S. Navy. USIS 95
Tactical Communications (TACO) A communications protocol commonly used in secondary imagery dissemination systems. USIS 95
Tactical Communications Protocol Version 2.0 (TACO2) Supports simplex, point-to-point and half- or full- duplex communications in either synchronous or asynchronous mode at the physical layer. TACO2 is compatible with any transmission rate. USIS 95
Tactical Digital Facsimile A part of the Intra-theater Imagery Transmission System (IITS) designed to give tactical commanders high-quality pictorial and documentary information in near-real time. USIS 95
Tactical Exploitation of National Capabilities (TENCAP) Service programs to review uses of national imagery. USIS 95
Tactical High Mobility Terminal A scaled-down version of the Enhanced Tactical Users Terminal (ETUT). This system, coupled with an imagery interface unit, is intended to provide secondary imagery dissemination below corps level. USIS 95
Tactical Information Processing and Interpretation System A tactical, mobile, land-based, automated information-handling system designed to store and retrieve intelligence information and to process and interpret imagery or nonimagery data. USIS 95
tactical input segment The segment for interfacing the Joint Service Imagery Processing System (JSIPS) to the tactical airborne systems. USIS 95
tactical intelligence (TACINTEL) (DOD) Intelligence that is required for planning and conducting tactical operations. See also intelligence; operational intelligence (OPINTEL); strategic intelligence. JPUB 1-02
tactical intelligence and related activities (TIARA) (DOD) Those activities outside the National Foreign Intelligence Program (NFIP) that: a. respond to operational commanders' tasking for time-sensitive information on foreign entities; b. respond to national intelligence community tasking of systems whose primary mission is support to operating forces; c. train personnel for intelligence duties; d. provide an intelligence reserve; or e. are devoted to research and development of intelligence or related capabilities. Specifically excluded are programs which are so closely integrated with a weapon system that their primary function is to provide immediate-use targeting data. JPUB 1-02
Tactical Internet An effort to provide reliable, seamless communication connectivity in the battlefield using commercial Internet technology such as routers, gateways and Internet protocols. DII MP
tactical map (JCS) A large-scale map used for tactical and administrative purposes. See also map. HDBK-850
Tactical Ocean Data (TOD™) TOD is a vector-based digital product that portrays seafloor configuration, particicularly in areas deeper than 183 meters (100 fathoms) in a format suitable for computerized subsurface navigation. It is designed to be used in conjunction with the Digital Nautical Chart (DNC™) for complete navigation information. TOD is based on the feature content of the Bathymetric Naval Planning Chart (BNPC). TOD is a general purpose global database designed to support subsurface navigation and geographic information system (GIS) applications. NIMA Web Site
Tactical Pilotage Chart (TPC) A 1:500,000 scale, coordinated series of multicolored charts which are produced in selected areas of interest. Designed to satisfy visual and radar navigation of high speed tactical aircraft operating at low altitude. Also used for detailed preflight planning and mission analysis. HDBK-850
tactical planning model Medium- or large-scale models providing considerable detailed terrain information; generally used for planning operations of a tactical nature. HDBK-850
Tactical Radar Correlator A mobile, self-contained system capable of receiving and processing Advanced Synthetic Aperture Radar System-2 (ASARS-2) all-weather, high-resolution, radar data into imagery that is exploited to provide tactical intelligence for the field commander. USIS 95
Tactical Terrain Analysis Data Base (TTADB) A set of transparent overlays keyed to 1:50,000 Tactical Line Maps (TLMs) portraying natural and cultural features of military significance. The data base consists of overlays and supporting data for: surface configuration (slope), surface materials (soils), vegetation, surface drainage, transportation, and obstacles. TTADBs provide terrain and man-made information to support the generation of a variety of field user produced synthesized products to include: Lines of Communication, Cross-Country Movement, and Cover & Concealment. HDBK-850
Tactical Terrain Data (TTD) The basic digital operational terrain data set supporting future land combat. TTD will be a value added database allowing for the addition and update of data by the user. Features and attributes are coded using categories contained in the Feature Attribute Coding System. TTD will contain contents of TTADB thematic overlays, as well as selected features from TLMs and Combat Charts. See also Tactical Terrain Analysis Data Base. HDBK-850
Tagged Image File Format (TIFF) A standard file format used to capture graphic images. TIFF stores images in bit mapped (raster graphics) format. USIS 95
tailoring guidance Guidance concerning a specific information processing standard on the specific features, modes, switch settings, functions, areas of deficiencies, extensions, levels, and options. This information is provided to tailor the specification for use to exploit it best for eventual transportability at the source code level. ITSG Vol. 1
tan alt See shadow factor. HDBK-850
tangent (surveying) 1. That part of a traverse or alignment included between the point of tangency of one curve and the point of curvature of the next curve. 2. A great circle line tangent to a parallel of latitude at a township corner. 3. Sometimes applied to a long straight line of a traverse, especially on a route survey, whether or not the termini of the line are points of curve. HDBK-850
tangent conical map projection See conic map projection. HDBK-850
tangent distance The distance from the point of intersection (vertex) of a curve to its point of tangency or point of curvature. HDBK-850
tangent plane A plane that touches a curved surface of double curvature at one and only one point or that touches a curved surface of single curvature along one or more parallel straight lines which are elements of the surface, without intersecting the surface. In geodetic work, a plane tangent to the spheroid at any point is perpendicular to the normal at that point. HDBK-850
tangent plane grid system (engineer surveying) A grid system in a tangent plane with origin at the point of tangency. Usually the origin is designated 10,000 N and 10,000 E, or some similar amounts, to keep all coordinates positive. This system never extends for any great distance, See also plane rectangular coordinates. HDBK-850
tangent to spiral (TS) The point at the end of a tangent and the beginning of a spiral. HDBK-850
tangential distortion Linear displacement of image points in a direction normal to radial lines from the center of the field. HDBK-850
tape (surveying) A ribbon of steel, Invar, specially made cloth, or other suitable material on which graduations are placed for the measurement of lengths or distances. See also adding tape; base tape; instantaneous reading tape; Invar tape; Lovar tape; piano-wire tape; subtracting tape. HDBK-850
tape corrections Quantities applied to a taped distance to eliminate or reduce errors due to the physical condition of the tape and to the way in which it is used. See also alignment correction; grade correction; length correction; sag correction; temperature correction, definition 3; tension correction. HDBK-850
tape gage A device consisting of a tagged or indexed chain, tape, or other line used for measurement or testing. Gage height or measurement is read on a graduated staff or index. Also called chain gage. HDBK-850
tape rod A rod consisting of a frame with rollers at both ends over which an endless, graduated metal tape moves. It is designed to permit direct readings by the instrument man, eliminating all addition and subtraction functions required by other types of rod readings. Also called automatic rod. HDBK-850
tape stretcher A mechanical device which facilitates holding a tape at a prescribed tension and in a prescribed position. Also called stretching apparatus. HDBK-850
tape thermometer A precision thermometer fitted in a specially designed case to clip on and against a metal tape in order to determine temperature corrections for precision base or traverse tape measurements. HDBK-850
taping The operation of measuring distances on the ground with a tape or chain. Formerly the words chaining and taping were used synonymously, but the word taping is now preferred for all surveys except those of the public land system. For the latter, because of historical and legal reasons, the term chaining is preferred. HDBK-850
taping arrow See pin. HDBK-850
taping buck See taping stool. HDBK-850
taping pin See pin. HDBK-850
taping station The stake marking each interval (one tape length) along a traverse from the initial point along road centerlines and similar survey operations. See also plus station. HDBK-850
taping stool A metal stool used for precise taping operations. Stools are portable and provide a stable elevated table on which the positions of the survey tape ends can be accurately marked. Also called taping buck. HDBK-850
tare An abrupt offset in the gravimeter normal reading level. HDBK-850
target 1. (JCS) A geographical area, complex, or installation planned for capture or destruction by military forces. 2. An object which reflects a sufficient amount of a radiated signal to produce an echo signal on detection equipment. 3. The distinctive marking or instrumentation of a ground point to aid in its identification on a photograph. In photogrammetry, target designates a material marking so arranged and placed on the ground as to form a distinctive pattern over a geodetic or other control point marker, on a property corner or line, or at the position of an identifying point above an underground facility or feature. A target is also the image pattern on aerial photographs of the actual mark placed on the ground prior to photography. See also area target; pinpoint target. HDBK-850
target A point or area on the earth's surface that has been assigned a unique identifier consisting of (in the case of a facility) a combination Basic Encyclopedia (BE) number, suffix, and Intelligence Data Handling System (IDHS) category code, (in case of an installation) a BE number, (in the case of an area target) an Area ID. Also see point target. USIS 2-1.1
target & geodetic data Information used to determine as accurate a location as possible. Data includes world datum, elevations, control position, etc. USIS 95
target accounting unit Used for tracking target satisfaction and accomplishment. USIS 95
target acquisition 1. (JCS) The detection, identification, and location of a target in sufficient detail to permit the effective employment of weapons. See also target analysis. 2. The process of optically, manually, mechanically, or electronically orienting a tracking system in direction and range to lock on a target. HDBK-850
target age The time interval since the target was last imaged successfully. USIS 95
target analysis (JCS) An examination of potential targets to determine military importance, priority of attack, and weapons required to obtain a desired level of damage or casualties. See also target acquisition. HDBK-850
target architecture The set of capabilities identified for the United States Imagery System (USIS) at a given point in time. A mapping of technical elements to organization types for a specific evolutionary step toward the objective USIS. USIS 95
target area survey base (JCS) A base line used for the locating of targets or other points by the intersection of observations from two stations located at opposite ends of the line. HDBK-850
target collection Collection of imagery data by one (or multiple) imaging system(s) to satisfy intelligence reporting. USIS 95
target complex (JCS) A geographically integrated series of target concentrations. See also target. HDBK-850
target concentration (JCS) A grouping of geographically proximate targets. See also target; target complex. HDBK-850
Target Data Inventory A basic targeting program that provides a standardized target data in support of the requirements of the Joint Chiefs of Staff, military departments, and Unified Commands for target planning coordination and weapons application. USIS 95
target diameter The diameter of the smallest circle that would contain the entire target. USIS 95
target dossiers (JCS) Files of assembled target intelligence about a specific geographic area. HDBK-850
target elevation The elevation (in meters or feet) that a target is above or below sea-level. USIS 95
target ellipse Defined by the major axis, minor axis, and major axis angle around the centroid of a point target. It bounds the entire area of the target. USIS 95
target emphasis A special, temporary priority assigned to a target on a daily basis to enhance collection probability. USIS 95
target folders (JCS) The folders containing target intelligence and related materials prepared for planning and executing action against a specific target. HDBK-850
target intelligence (JCS) Intelligence which portrays and locates the components of a target or target complex and indicates its vulnerability and relative importance. HDBK-850
target leveling rod A type of leveling rod, carrying a target, which is moved into position according to signals given by the instrument man; when the target is bisected by the line of collimation of the instrument, it is read and recorded by the rodman. See also double-target leveling rod; single-target leveling rod. HDBK-850
target location Latitude and longitude of target in degrees, minutes, and seconds. USIS 95
target material graphics See target materials. HDBK-850
target materials (JCS) Graphic, textual, tabular, or other presentations of target intelligence, primarily designed to support operations against designated targets by one or more weapon systems. Target materials are suitable for training, planning, executing, and evaluating such operations. Also called target material graphics. See also Air Target Chart (ATC). HDBK-850
Target Materials Program (TMP) 1. A DoD program established for the production of all documents specifically supporting installation target analysis and operational planning employment. The DoD overall TMP manager is DIA. 2. The production programs responding to the JCS charter for NIMA to produce unique, critical geo-locational information supporting the long-range worldwide requirements of the unified and specified commands, military departments, and allied participants. [The program consists of precision point location products such as the Installation Reference Point Graphic (IRPG), Aim Point Graphic (APG), and grid photos; deployable Point Positioning Data Base (PPDB) in either film, video, or digital form; cartographic Air Target Materials like the Air Target Chart (ATC) and Joint Operations Graphic - Radar (JOG-R); and a variety of other special materials and services.] HDBK-850
Target Materials Workstation A closed-network computer system designed to digitally manipulate intelligence information, imagery, maps, and charts to produce target materials in support of the DIA-coordinated Tactical Target Materials Program. USIS 95
target positioning data The accurate horizontal and vertical values which define the location of a target or point. See also precise installation position; precise radar significant location. HDBK-850
target reference data Data that pertain to the target (i.e., IDs, location, size, elevation, etc.). USIS 95
target report An account or analysis of imagery derived information pertaining to a single target. USIS 2-1.1
target set A group of targets having homogeneous requirements for collection, processing, distribution, exploitation, or other logical reason. USIS 95
target system (JCS) All the targets situated in a particular geographic area and functionally related. See also target complex. HDBK-850
target system component (JCS) A set of targets belonging to one or more groups of industries and basic utilities required to produce component parts of an end product such as periscopes, or one type of a series of interrelated commodities, such as aviation gasoline. HDBK-850
target value categories When appropriate, targets with a homogeneous population (e.g., ground troop installations) should be categorized according to their relative value to the intelligence problem. This facilitates the placement of collection emphasis on the targets that could be expected to best support resolution of the intelligence problem. The categories normally used are: key targets, major targets, and regular (other) targets. The majority of targets should fall into the regular or other category with only a very few designated as major or key. USIS 95
targeting 1. The process of selecting targets and matching the appropriate response to them, taking account of operational requirements and capabilities. 2. The analysis of enemy situations relative to the commander's mission, objectives, and capabilities at the commander's disposal, to identify and nominate specific vulnerabilities that, if exploited, will accomplish the commander's purpose through delaying, disrupting, disabling, or destroying enemy forces or resources critical to the enemy. USIS 95
task A discrete unit of work, not specific to a single organization, weapon system, or individual, that enables missions or functions to be accomplished. (Extension from UJTL, JCSM 3500.04A, 1996) Note: Multiple processes accomplish a task; a single process may support multiple tasks. (SPAWAR) C4ISR AF
tasking The direction to perform, or the assignment of responsibility for the performance of, a specified imagery collection, interpretation, reporting, or related support function. USIS 95
tasking, processing, exploitation, and dissemination (TPED) See tasking, processing, exploitation, and dissemination. NIMA/AR
taut-wire apparatus A 100-meter stranded sounding wire, graduated at 25-meter intervals, used to measure the distances between offshore control buoys during a hydrographic survey. HDBK-850
TCP/IP Gateway A device, or pair of devices, that interconnects two or more networks or subnetworks, enabling the passage of data from one (sub)network to another. In this architecture, a gateway contains an IP module and, for each connected subnetwork, a subnetwork protocol (SNP) module. The routing protocol is used to coordinate with other gateways. A gateway is often called an IP router. TAFIM 3.0
Technical Architecture Framework for Information Management (TAFIM) The TAFIM is a set of documents produced by DISA for the OSD to guide DOD information systems toward an open systems architecture. It provides the services, standards, design concepts, components, and configurations that can be used to guide the development of technical architectures that meet specific mission requirements. DISA CFS
technical architecture view The technical architecture view is the minimal set of rules governing the arrangement, interaction, and interdependence of system parts or elements, whose purpose is to ensure that a conformant system satisfies a specified set of requirements. The technical architecture view provides the technical systems-implementation guidelines upon which engineering specifications are based, common building blocks are established, and product lines are developed. The technical architecture view includes a collection of the technical standards, conventions, rules and criteria organized into profile(s) that govern system services, interfaces, and relationships for particular systems architecture views and that relate to particular operational views. C4ISR AF
Technical Reference Model (TRM) {DoD} The document that identifies a target framework and profile of standards for the DoD computing and communications infrastructure. See also reference model. TAFIM 3.0
technology model A term used to define and describe the components of the technology infrastructure that support the other architecture models. It is in this area that the enabling effect of standards-based architectures is felt the most. The technology model provides the technology managers' views of the architecture. TAFIM 3.0
technology viewpoint A viewpoint on a system and its environment that focuses on the choice of technology in that system. RM-ODP
teleconference A conference between persons remote from one another but linked by a telecommunications system. [JITC Dictionary] DISA CFS
teleconferencing The use of electronic channels to facilitate real-time communications among groups of people at two or more locations. Teleconferencing is a generic term that refers to a variety of technologies and applications, including audio conferencing, audiographics conferencing, video conferencing, business television, and distance learning or distance education. Multimedia
telemeter (surveying) An instrument for determining the distance from one point to another. Some such instruments employ a telescope and measure the angle subtended by a short base of known length. See also electronic telemeter; telemetry. HDBK-850
telemetry The science of measuring a quantity or quantities, transmitting the measured value to a distant station, and there interpreting, indicating, or recording the quantities measured. HDBK-850
telemetry intelligence (TELINT) (DOD) Technical intelligence derived from the intercept, processing, and analysis of foreign telemetry. Telemetry intelligence is a category of foreign instrumentation signals intelligence. See also electronics intelligence (ELINT); intelligence; foreign instrumentation signals intelligence (FISINT). JPUB 1-02
telephonic report The imagery-derived information transmitted by voice or fax over a telephone, facsimile, radio or other communications device. USIS 95
telescope An optical instrument used as an aid in viewing or photographing distant objects, particularly celestial objects. See also achromatic telescope; erecting telescope; inverting telescope; meridian telescope; zenith telescope. HDBK-850
telescope level A spirit level attached to a telescope, with its axis parallel to the telescope axis. HDBK-850
telescopic alidade A usual designation for an instrument composed of a telescope mounted on a straightedge ruler, and used with a planetable in topographic surveying. HDBK-850
telescoping See transit, definition 3. HDBK-850
telluroid A surface near the terrain being the locus of points in which the spheropotential is the same as the geopotential of corresponding points on the terrain. Its distance from the spheroid is the normal height. HDBK-850
Tellurometer A trade name for a microwave distance-measuring system in which the velocity of a radio wave is used to determine the distance between two instruments operating alternately as master station (interrogator) and remote station (responder). HDBK-850
Telnet The TCP/IP standard network virtual terminal protocol that is used for remote terminal connection service and that allows a user at one site to interact with systems at other sites as if that user terminal were directly connected to computers at those sites. FED STD 1037C
temperature correction 1. (leveling) That correction which is applied to an observed difference of elevation to correct for the error introduced when the temperature at which the leveling rods are used in the field is different from the temperature at which they were standardized. 2. (pendulum) The quantity that is applied to the period of vibration of a pendulum to allow for the difference in the length of the pendulum at the temperature of observation and its length at some other temperature which has been adopted for purposes of standardization or for combining or comparing corresponding values. 3. (taping) The quantity applied to the nominal length of a tape to allow for a change in its effective length due to its being used at a temperature other than that for which its standard length is given. HDBK-850
template The specification of the common features of a collection of entities in sufficient detail that an entity can be instantiated using it. For example, an object template is the specification of the common features of a collection of objects in sufficient detail that an object can be instantiated using it. A object template is an abstraction of a collection of objects. A template may specify parameters to be bound at instantiation time. A standards specification containing interface bindings is a technology object template. RM-ODP
templet (template) 1. A pattern or guide, usually constructed of paper, plastic, or metal, used to shape, delimit, or locate an area. 2. A device used in radial triangulation to represent the aerial photograph; the templet provides a record of the directions of radials taken from the photograph. See also calibration templet; double-model stereotemplet; hand templet; Hayford deflection templets; Hayford gravity templets; mechanical templet; slotted templet; spider templet; stereotemplet. HDBK-850
templet cutter A mechanical device for punching center holes and slots in templets. The slots are centered on points transferred from aerial photographs and are radial to the center hole. Also called secator; slot cutter; radial secator. HDBK-850
templet laydown The process of assembling individual slotted templets into a radial control net. HDBK-850
templet method Any of the various methods utilized in graphical radial triangulation. HDBK-850
templet ratiograph (photogrammetry) A device for determining the ratio in decimals between two distances. One distance is that between the principal point and another designated point on the aerial photograph. The other is the corresponding distance between the principal point on a templet and the marked center of the stud for the designated point upon completion of the templet laydown. The ratiograph is designed for a specific templet cutter. See also ratiometer. HDBK-850
temporal accuracy The primary quality parameter indicating the accuracy of temporal properties of a geographic subset. CEN/TC 287
temporal attribute A feature attribute describing the temporal characteristics of the feature. ISO/TC 211
temporal characteristic A feature attribute or a metadata element which has a reference to time in its name and definition and a value in the time domain. ISO/TC 211
temporal coordinate The distance of an instant from the origin of an interval in time scale. ISO/TC 211
temporal coordinate system A temporal reference system based on an interval scale defined in terms of a single standard interval. ISO/TC 211
temporal extent Extent in time of a dataset. CEN/TC 287
temporal position The location of a temporal primitive to a temporal reference system. ISO/TC 211
temporal primitive A basis geometric element in the temporal dimension. ISO/TC 211
temporal reference system A basis against which time is measured. ISO/TC 211
temporary bench mark (TBM) A bench mark at a junction of sections of a line of levels, at which no permanent bench mark is established. Also called nonmonumented bench mark; supplementary bench mark. HDBK-850
tension correction (taping) The correction applied to the nominal length of a tape to allow for a change in effective length due to its being used at a tension other than that for which its standard length is known. HDBK-850
term Designation of a concept. This may be the object type name or any level of generalization of the object type. CEN/TC 287
terminal From the user's viewpoint, a terminal is a device, instrument, or facility used to generate, transmit, and receive traffic in one or more of several modes via a transmission line directly to or from another terminal or via a network to or from a distant subscriber; normally organic to the user or his direct support organization. Also defined as a facility where channels or circuits may be tested, rerouted, dropped out, or inserted. [Joint Pub 6-02.1] DISA CFS
Terminal Access Controller (TAC) A host computer that accepts terminal connections, usually from dial-up lines, and that allows the user to invoke Internet remote log-on procedures, such as Telnet. FED STD 1037C
terminating node A connected node terminating an edge. ISO/TC 211
terrain An area of ground considered as to its extent and topography. HDBK-850
terrain analysis (TA) (NATO) The process of collecting, analyzing and evaluating geographic information on the natural and man-made features of the terrain and its interpretation in combination with other factors to provide predictive information and advice about the effect of the terrain on military operations. HDBK-850
Terrain Analysis Products (TAP) (NATO) A standardized or non-standardized product from the Terrain Analysis System normally presented in graphic form for use in military decision making. HDBK-850
Terrain Analysis System (TAS) (NATO) A system to meet military requirements for quick and comprehensive information on the terrain in analog and/or digital form. It is a system in which selected data about the terrain are collected and stored in a structured way to permit their flexible exploitation in the provision of Terrain Analysis Products. HDBK-850
terrain contour matching (TERCOM) The process which updates navigational guidance systems through correlation with gridded terrain elevation data derived from photogrammetric or large scale cartographic sources. See also terrain correlation. [TERCOM is also used to refer to the digital product used to perform this process in the guidance system of cruise missles] HDBK-850
terrain correction A positive correction used in conjunction with other corrections in making gravity reductions. It takes into account actual deviations from level terrain in the area surrounding a station by removing masses above the horizon and filling in mass deficiencies below. Also called topographic correction. HDBK-850
terrain correlation A process used by a vehicle's guidance system in evaluating the elevations of the terrain it is flying over and comparing it with prestored digital terrain elevation data. See also terrain contour matching. HDBK-850
Terrain Edit Station/Elevation Matrix Processing System (TES/EMPS) An Intergraph workstation used by DMA [NIMA] to edit terrain products. Gives both plan and perspective views. HDBK-850
terrain emboss A model-making technique for portraying relief on a chart. A photographic process is used to produce the shaded relief effect from an embossed model. HDBK-850
terrain following The flight mode by which a vehicle maintains a specified altitude above the Earth's surface. HDBK-850
terrain intelligence (JCS) Processed information on the military significance of natural and man-made characteristics of an area. HDBK-850
terrain model A three-dimensional graphic representation of an area, showing the conformation of the ground, modeled to scale and usually handpainted to depict realistically man-made and natural physical features. The vertical scale is usually exaggerated, without severe distortion, to accentuate the aspect of relief. HDBK-850
terrain profile photography Cartographic photography obtained simultaneously with positional camera photography and recording of data relating to profile elevation information of the terrain along or near the ground track of the aircraft. The terrain profile recorder is normally used as the measuring device. HDBK-850
Terrain Profile Recorder (TPR) An electronic instrument that emits a pulsed-type radar signal from an aircraft to the Earth's surface, measuring vertical distances in order to obtain a profile beneath the track of the aircraft. Also called Airborne Profile Recorder. See also laser terrain profile recorder. HDBK-850
terrain profiling Obtaining an elevation profile of the Earth's terrain along or near the ground track of the aircraft by use of a Terrain Profile Recorder. HDBK-850
terrain slope Terrain slope value is the change in height per unit distance along the maximum terrain slope at the target. The terrain slope is always positive. The terrain slope normally points upward. USIS 95
terrain slope azimuth The angle, measured in a clockwise direction, from true north to the projection of the terrain slope normal on the horizontal plane. USIS 95
terrain study (JCS) An analysis and interpretation of natural and manmade, their effects on military operations, and the effect of weather and climate on these features. HDBK-850
terrestrial camera A camera designed for use on the ground. Also called ground camera. HDBK-850
terrestrial coordinates See geographic coordinates. HDBK-850
terrestrial equator See astronomic equator; geodetic equator. HDBK-850
terrestrial globe A sphere, on the outer surface of which, by means of symbols and reference lines, the features of the surface of the Earth are shown in relative positions. HDBK-850
terrestrial latitude Latitude on the Earth; angular distance from the Equator. HDBK-850
terrestrial longitude Longitude on the Earth; the arc of a parallel, or the angle at the pole, between the prime meridian and the meridian of a point on the Earth. HDBK-850
terrestrial magnetism See geomagnetism. HDBK-850
terrestrial meridian See astronomic meridian. HDBK-850
terrestrial perturbations The largest gravitational perturbations of artificial satellites which are caused by the fact that the gravity field of the Earth is not spherically symmetrical. HDBK-850
terrestrial photogrammetry Photogrammetry utilizing terrestrial photographs. Also called ground photogrammetry. HDBK-850
terrestrial photograph A photograph taken by a camera located on the ground. Also called ground photograph. HDBK-850
terrestrial planet A planet that approximates the Earth in size (Mercury, Venus, Mars, and Pluto) and physical makeup. HDBK-850
terrestrial pole See geographical pole. HDBK-850
terrestrial refraction The refraction by the Earth's atmosphere of light from a terrestrial source. The path of light from a terrestrial source is usually not far from horizontal; it passes through only the lower strata of the atmosphere and suffers refraction throughout its entire length. See also atmospheric refraction; horizontal refraction; lateral refraction. HDBK-850
terrestrial sphere The Earth. HDBK-850
terrestrial triangle A triangle on the surface of the Earth, especially the navigational triangle. HDBK-850
tesla (geomagnetism) The electromagnetic unit of magnetic induction. 1 tesla = 10-9 nanotesla. See also gauss. HDBK-850
Tesselated Spheroid Model-IV (TS) A coordinate system which divides the world into 5 latitude zones to obtain equal spacing. HDBK-850
tessellation Total coverage of an area by geometric figures of the same size and shape, with no overlaps. NOTE - The tessellation is regular if formed by repeating a regular polygon such as a square, equilateral triangle, or regular hexagon. The tessellation is nearly regular if formed by repeating the pattern of an "almost" regular polygon, such as a non-square rectangle, non-rectangular parallelogram, or non-equilateral triangle. ISO/TC 211
tesseral harmonics The set of all spherical harmonics that are functions of both latitude and longitude. Sectorial harmonics are a special subset of tesseral harmonics. HDBK-850
test campaign The process of running the executable test suite for a particular IUT. ISO/TC 211
test chart See resolving power target. HDBK-850
test purpose A precise description of an objective which an abstract test case is designed to achieve. ISO/TC 211
test range support NIMA provided geodetic surveys for the DoD test and training ranges to support weapons systems and weapons systems users research, development, testing and evaluation. HDBK-850
text-based systems Method of organization in which the primary form of interaction between the system and user is through text rather than through graphical or voice interaction. [HCI Style Guide] DISA CFS
textual fidelity The secondary quality parameter indicating the correctness of text within a geographic subset. CEN/TC 287
texture In a photo image, the frequency of change and arrangement of tone. HDBK-850
The Global Topography Mission (TOPSAT) TOPSAT will include an interferometric synthetic aperture radar (INSAR), a multibeam laser altimeter (MBLA) and a global positioning system (GPS) receiver. The INSAR will obtain a global digital elevation data set in less than 6 months, with high resolution (30m) and high vertical accuracy (less than 5m). The MBLA will obtain a globally distributed grid of narrow altimeter swaths of very high accuracy (less than 1 m in low-relief terrain for verifying the geodetic control of the INSAR data, for mapping of the polar ice sheets, and for measurement of vegetation height and surface roughness in selected areas. TOPSAT can be accomplished within the framework of NASA's Earth Probe program and be ready to launch in the 1998-2000 timeframe. USIS 95
The Open Group The Open Group is the leading vendor-neutral, international consortium for buyers and suppliers of technology. Through its Customer and Software Councils, The Open Group provides an arena where organizations can make their voice heard, influencing the delivery of standard specifications and future product development to ensure conformance to the basic features of an agreed open environment. The Open Group's mission is "to cause the development of a viable global information infrastructure that is ubiquitous, trusted, reliable and as easy to use as the telephone." Open Group Web Site
theater The geographical area outside the continental United States for which a commander of a combatant command has been assigned responsibility. USIS 95
Theater Mission Planning System Imagery support system used to produce digitized guidance imagery carried by the TOMAHAWK cruise missile. USIS 95
thematic accuracy The primary quality parameter indicating the accuracy of thematic properties of a geographic subset. CEN/TC 287
thematic attribute A feature attribute describing any characteristic of a feature except those covered by spatial and temporal primitives. ISO/TC 211
thematic map See topical map. HDBK-850
thematic mapper ™ A seven-channel, predominantly 30 meter instantaneous field of view (IFOV) multispectral scanner, designed for monitoring earth resources. TM is used on board LANDSAT satellites. HDBK-850
thematically separate The segregation of a feature or a limited number of features within a data base to highlight the spatial characteristics of a subset or the environment. See also layer. HDBK-850
theme (UCDM Entity: "THEME") A grouping of related types of features. USIGS/CDM-A
theodolite A precision surveying instrument consisting of an alidade with a telescope. It is mounted on an accurately graduated circle and is equipped with necessary levels and reading devices. Sometimes, the alidade carries a graduated vertical circle. See also cine theodolite; direction instrument theodolite; gyrotheodolite; phototheodolite; repeating theodolite. HDBK-850
theodolite magnetometer An instrument used in magnetic surveys consisting of a theodolite and a magnetometer modified to fit into a common base, which permits the determination of the true meridian and the magnetic meridian in a single observation. HDBK-850
theoretical corner A term adopted by the U.S. Geological Survey to designate the corners on the map for which no marks are identified on the ground. The locations are determined by adjustment and are indicated on the map only by the intersection of the subdivision lines. HDBK-850
theoretical error A systematic error arising from natural physical conditions, beyond the control of the observer. See also external error. HDBK-850
theoretical gravity The value of gravity calculated for a particular latitude according to an accepted formula. See also formula for theoretical gravity. HDBK-850
theory of anharmonic ratio A theory principally concerned with the processes of transformation and rectification whereby projectively related figures possess certain metric characteristics which are invariant under projection. Also called theory of cross ratio. HDBK-850
theory of cross ratio See theory of anharmonic ratio. HDBK-850
thermal crossover The natural phenomenon that normally occurs twice daily when temperature conditions are such that there is a loss of contrast between two adjacent objects on infrared imagery. USIS 95
thermal imagery (JCS) Imagery produced by sensing and recording the thermal energy emitted or reflected from the objects which are imaged. HDBK-850
thermal models An engineering system simulation of the end-to-end operational process that employs thermal properties of a target object, facility, or any other activity requiring comprehensive analytical assessment. USIS 95
thermometric leveling The determination of elevations above sea level from observed values of the boiling point of water. A type of indirect leveling. HDBK-850
thermometry The process in which radiance data are used to estimate the target's temperature characteristics. USIS 95
thesaurus Lexicon describing the classification of a dataset. In a thesaurus multiple hierarchies are permitted. CEN/TC 287
thesaurus element An entry within a thesaurus. This is composed of a term, its definition, synonyms, terms related to the term, a broader term, a narrow term, and an optional picture. CEN/TC 287
thick lens A term used in geometrical optics to indicate that the thickness of a lens is considered and that all distances are being measured from the nodal points instead of the lens center. HDBK-850
thin lens A term used in geometrical optics to indicate that the thickness of a Iens is ignored and that all distances are measured from the Iens center; used for approximate computations. HDBK-850
thinning The process whereby a linear feature is generalized through the use of a series of rules that reduces the number of data points while maintaining the basic shape of the feature. HDBK-850
third phase exploitation reporting The in depth analysis of all available imagery pertinent of a specific intelligence requirement, and the reporting of results within a specified time. The purpose of third phase exploitation and reporting is to provide an organized, in depth analysis of a target or topic, using imagery as the primary data source but incorporating data from other sources as appropriate. USIS 2-1.1
third-order leveling Spirit leveling which does not attain the quality of second-order leveling, but does conform to the current specifications for third-order leveling per "Classification Standards of Accuracy and General Specifications of Geodetic Control Surveys." Recommended for most general vertical control purposes within a limited area. HDBK-850
third-order traverse A survey traverse which extends between adjusted positions of other control surveys which conform to the current specifications for third-order (class I or class II) triangulation per "Classification Standards of Accuracy and General Specifications of Geodetic Control Surveys." Recommended for most general horizontal control purposes within a limited area. HDBK-850
third-order triangulation Formerly known as tertiary triangulation, these surveys conform to current specifications for third-order (class I or class II) triangulation per "Classification Standards of Accuracy and General Specifications of Geodetic Control Surveys." Recommended for most general horizontal control purposes within a limited area. HDBK-850
third-order work This is the lowest order of control surveys for which monumentation is authorized. HDBK-850
thread A single flow of control within a process. IEEE P1003.0
three sigma (3S ) The 99.73 percent confidence interval of a distribution. See also standard error. HDBK-850
three-arm protractor A full-circle protractor, equipped with three arms, the fiducial edges (extended) of which pass through the center of the circle. The middle arm is fixed and reads 0 on the graduated circle. The other arms are movable, and their positions on the circle are read with the aid of verniers. The two movable arms are equipped with clamps and may be set at any angle with respect to the fixed arm, within the limits of the instrument. It is used for finding a (ship's) position graphically when the angles between three known fixed points are available. Also called station pointer. HDBK-850
three-body problem That problem in classical celestial mechanics which treats the motion of a small body, usually of negligible mass, relative to and under the gravitational influence of two other finite point masses. HDBK-850
three-dimensional (3-D) data Volumetric data representing measurements in three dimensions, as angular or linear measures such as phi-lambda-kappa or latitude-longitude-elevation. HDBK-850
three-dimensional (3-D) models A physical representation of a target or object, based primarily on imagery, that can depict natural and/or man-made elements in addition to relief and/or elevation data. USIS 95
three-point method See resection. HDBK-850
three-point problem The determination of the horizontal position of a point of observation from data comprising two observed horizontal angles between three objects of known position. The problem is solved graphically by the use of a three-arm protractor, and analytically by trigonometrical computation. See also resection; triangle-of-error method. HDBK-850
three-wire leveling A method of Ieveling applied when the reticle of the Ievel has three lines. The rod is read at each of the three lines and the average is used for the final result with an accuracy as great as if three lines of levels had been run and the results averaged. HDBK-850
thumbnail A reduced resolution version of an image. USIS 95
ticks See register marks. HDBK-850
tidal bench mark A bench mark set to reference a tide staff at a tidal station and the elevation of which is determined with relation to the local tidal datum. HDBK-850
tidal constituent See constituent. HDBK-850
tidal correction A correction applied to gravitational observations to remove the effect of Earth tides on gravimetric observations. HDBK-850
tidal current The alternating horizontal movement of water associated with the rise and fall of the tide caused by the astronomic tide-producing forces. HDBK-850
tidal current chart A chart showing, by arrows and numbers, the average direction and speed of tidal currents at a particular part of the current cycle. A number of such charts, one for each hour of the current cycle, usually are published together. HDBK-850
tidal datum Specific tide levels which are used as surfaces of reference for depth measurements in the sea and as a base for the determination of elevation on land. Many different datums have been used, particularly for leveling operations. Also called tidal datum plane. HDBK-850
tidal datum plane See tidal datum. HDBK-850
tidal day See lunar day. HDBK-850
tidal variation of gravity Periodic deviations from normal of the gravity on Earth and the direction of the plumb line caused by the attraction of the Moon and the Sun's mass. HDBK-850
tide The periodic rise and fall of the surface of the ocean resulting from the gravitational attraction of the Moon and Sun acting upon the rotating Earth. See also age of diurnal inequality; age of parallax inequality; age of phase inequality; amphidromic point; amphidromic region; annual inequality; anomalistic tide cycle; apogean tides; constituent; constituent day; corrected establishment; cotidal hour; degenerate amphidromic system; diurnal constituent; diurnal inequality; ebb tide; establishment of the port; flood tide; harmonic constants; height of the tide; high water; high water line; higher high water; higher high water interval; higher low water; higher low water interval; Indian spring low water; Indian tide plane; international low water; low water; low water full and change; low water line; lower high water; lower high water interval; lower low water; lower low water interval; lowest low water; lowest low water springs; lunar day; lunar tide; lunitidal interval; mean diurnal high water inequality; mean diurnal low water inequality; mean high water; mean high water springs; mean higher high water; mean higher high water springs; mean low water; mean low water springs; mean lower low water; mean lower low water springs; mean range; mean river level; mean sea level; mean tide level; nodal line; parallax inequality; phase inequality; set; semidiurnal constituent; tidal correction; tidal current; tidemark. HDBK-850
tide gage A device for measuring the height of tide. It may be simply a graduated staff in a sheltered location where visual observations can be made at any desired time; or it may consist of an elaborate recording instrument making a continuous graphic record of tide height against time. Such an instrument is usually actuated by a float in a pipe communicating with the sea through a small hole which filters out shorter waves. See also float gage; nonrecording gage; portable automatic tide gage; pressure gage; self-registering gage; staff gage; standard automatic tide gage. HDBK-850
tide level See mean tide level. HDBK-850
tide over run A reprint of a chart or map necessitated by unusual conditions before extensive revisions can be accomplished. Also called emergency run. HDBK-850
tide station A place at which tide observations are made. See also primary tide station; secondary tide station. HDBK-850
tidemark 1. A high water mark left by tidal water. 2. The highest point reached by a high tide. 3. A mark placed to indicate the highest point reached by a high tide, or occasionally, any specified state of tide. HDBK-850
tide-producing force(s) The slight local difference between the gravitational attraction of two astronomic bodies and the centrifugal force that holds them apart. These forces are exactly equal and opposite at the center of gravity of either of the bodies, but, since gravitational attraction is inversely proportional to the square of the distance, it varies from point to point on the surface of the bodies. Therefore, gravitational attraction predominates at the surface point nearest to the other body, while centrifugal repulsion predominates at the surface point farthest from the other body. Hence, there are two regions where tide-producing forces are at a maximum, and normally there are two tides each lunar day and solar day. HDBK-850
tie A survey connection from a point of known position to a point whose position is desired. A tie is made to determine the position of a supplementary point whose position is desired for mapping or reference purposes, or to close a survey on a previously determined point. To "tie-in" is to make such a connection. See also tie point, definition 2. HDBK-850
tie flight See control strip. HDBK-850
tie point 1. Image points identified on oblique photographs in the overlap area between two or more adjacent strips of photography. They serve to tie the individual sets of photographs into a single flight unit and to tie adjacent flights into a common network. 2. Point of closure of a survey either on itself or on another survey. HDBK-850
tie strip 1. (cartography) An overlay containing all planimetric and relief features in the area along the edge of a map or chart. It is used to insure the matching of these features on adjoining sheets. Also called match strip. 2. (aerial photography) See control strip. HDBK-850
tie-in See tie. HDBK-850
tier Any series of contiguous townships situated east and west of each other; also sections similarly situated within a township. HDBK-850
tile The partition of a dataset based on the definition of a geographic area. CEN/TC 287
tiled coverage A coverage that has been physically partitioned into smaller coverages. One or more of these smaller coverages, where all share the same set of feature classes with the same definitions. Each tile defines an independent topology. HDBK-850
tiling scheme The scheme used to define tile shape and size, and unique tile identification number. HDBK-850
tilt (JCS) See roll. Also called angle of tilt. See also cross tilt; direction of tilt; pitch; relative tilt; x-tilt. HDBK-850
tilt angle (JCS) The angle between the optical axis of an air camera [or sensor] and the vertical at the time of exposure. See also angle of depression; tilt. HDBK-850
tilt circle In a tilted aerial photograph, a circle passing through the isocenter and having a diameter lying along the principal line. When this diameter is drawn to a convenient linear scale, then any chord through the isocenter gives the component of tilt for that particular direction. HDBK-850
tilt displacement Displacement radial from the isocenter of the photograph caused by the tilt of the photograph. HDBK-850
tilt slide rule A device which facilitates the determination for settings on a fixed-lens rectifier when certain tilt factors of an aerial photograph are known. HDBK-850
tilting level A leveling instrument in which the telescope with its attached bubble tube can be leveled by a fine screw at the eyepiece end of the telescope independently of the vertical axis, thus avoiding the need for careful leveling of the instrument as a whole. This type of level was first designed for precise work, but the principle has come into popular use for ordinary levels. HDBK-850
tilting-lens rectifier A class of rectifiers in which the principal point is fixed on its axis of swing, and cannot be displaced. HDBK-850
time (DOD) An epoch, i.e., the designation of an instant on a selected time scale, astronomical or atomic. It is used in the sense of time of day. See also apparent sidereal time; apparent solar time; astrograph mean time; astronomic time; atomic time; civil time; Coordinated Universal Time (UTC); day; ephemeris time; equation of time; Greenwich apparent time (GAT); Greenwich lunar time; Greenwich sidereal time (GST); Greenwich time; International Atomic Time (TAI); local apparent time; local astronomic time; local lunar time; local mean time; local sidereal time; local time; lunar time; mean sidereal time; mean solar time; month; rise time; sidereal time; solar time; standard time; Universal Time (UT1). JPUB 1-02
time diagram A diagram in which the celestial equator appears as a circle, and celestial meridians and hour circles as radial lines; used to facilitate solution of time problems and others involving arcs of the celestial equator or angles at the pole, by indicating relations between various quantities involved. Conventionally, the relationships are given as viewed from a point over the South Pole, westward direction being counterclockwise. Also called diagram on the plane of the equinoctial. See also diagram on the plane of the celestial meridian. HDBK-850
time distance Time required for any object to travel between two given points at a given rate of speed. HDBK-850
time gamma curve See characteristic curve. HDBK-850
time lag See access time lag. USIS 95
time meridian Any meridian used as a reference for reckoning time, particularly a zone or standard meridian. HDBK-850
time of closest approach The time at which the satellite and a ground point are closest to each other on a specific orbit. USIS 95
time of day The designation of a particular instant of time within a given calendar day ISO/TC 211
time phased force and deployment data The computer supported data base portion of an operation plan; it contains time phased force data, non unit related cargo and personnel data, and movement data for the operation plan, including: A. In place units. B. Units to be deployed to support the operation plan with a priority indicating the desired sequence for their arrival at the port of debarkation. C. Routing of forces to be deployed. D. Movement data associated with deploying forces. E. Estimates of non unit related cargo and personnel movements to be conducted concurrently with the deployment of forces. F. Estimate of transportation requirements that must be fulfilled by common user lift resources as well as those requirements that can be fulfilled by assigned or attached transportation resources. USIS 95
time phased force and deployment list Appendix 1 to Annex A of the operation plan. It identifies types and/or actual units required to support the operation plan and indicates origin and ports of debarkation or ocean area. It may also be generated as a computer listing from the time phased force and deployment data. USIS 95
time zone An area in all parts of which the same time is kept. In general, each zone is 15 of longitude in width, centered on a meridian whose longitude is generally divisible by 15. HDBK-850
time zone chart A small-scale chart of the world designed to show the legal time kept on land. HDBK-850
time-dominant requirements Refers to the nature of the urgency or priority with which processing and exploitation need to be addressed. Time-dominant requirements are those representing perishable information or information that concerns national security. Examples of time dominant requirements would be Indications and Warning or Support to Combat Operations. Generally, time dominant requirements are satisfied within 24 hours of receipt of imagery for department level exploitation, 6 hours for theater level and 15 minutes for unit level exploitation. USIS 95
time-on-target The local time when a collection platform has access to its objective. USIS 95
times (X) enlargement The multiplication factor by which an original is to be enlarged in reproduction. A two-times (2X) linear enlargement of a 4- by 5-inch original would be 8 by 10 inches. See also diameter enlargement; scale of reproduction. HDBK-850
timing correction A correction applied to the length of a trilateration measurement to compensate for the delay of the radar signal as it passes through the ground transponder unit of an electronic distance-measuring device. HDBK-850
tints Color gradations used on maps to designate depth or height. See also hypsometric tinting. HDBK-850
tip See pitch. HDBK-850
tipped panoramic distortion In a panoramic camera system, the displacement of images of ground points from their expected vertical panoramic positions caused by the tipping of the scan axis within the vertical plane of the flight path. This distortion is additive and modifies again the image positions of points already influenced by panoramic distortion, scan positional distortion, and image motion compensation distortion. HDBK-850
title block A space on a nonstandard graphic, such as a mosaic, photograph, or plan devoted to identification, reference, and scale information. HDBK-850
titling (title information) That information lettered on aerial photographic negatives for identification purposes. Also, the placing of such information on the negatives. Also called film titling; negative titling. HDBK-850
titling and marginal data Information included on a image that identifies characteristics of that image including image identification, classification, time of imaging, and orientation. USIS 95
TK-350 Camera [Russian] The TK-350 is a 10 meter resolution topographic camera with a 350mm focal length. It captures images at approximately 1:660,000 scale in a 30 cm by 45 cm format. The images cover an area of 200 km by 300 km but imagery is available in sub-frames. The TK-350 camera provides accurate surface elevation data with stereo imagery using the true stereo pairs produced through this 80% longitudinal overlap. The data is single band with a spectral range of 510-760 nm. See also KVR-1000 Camera and Space Information - 2 Meter (SPIN-2®). SPIN-2 Web Site
to object type The object type associated with another object type that is regarded as a from object type. CEN/TC 287
token ring The token ring LAN interface is specified by IEEE 802.5 and supports data rates of four Mbps or sixteen Mbps. It utilizes a ring topology and a token passing technique. [DISA/DO3 (CIO)] DISA CFS
Tokyo datum This datum, with its origin in Tokyo, is defined in terms of the Bessel ellipsoid. It also covers Korea and Okinawa. Note: In the absence of information to confirm that this datum is identical to the Old Tokyo Observatory Datum of 1918, the two datums are to be considered separately. HDBK-850
tolerance The maximum allowable variation from a standard or from specified conditions. HDBK-850
tonal transfer curve A family of curves used by an image processing or softcopy display system. A TTC is automatically used by a system as selected by an image analyst or other user of imagery products to optimally display an image, or when required to adjust brightness or contrast of an image to exploit information available in the shadows or highlight of that image. A TTC curve can be a linear or non-linear look up table, depending on the nature of sensor and scene dynamic range constraint, applied to a unique display monitor or hardcopy printer device combination. USIS 95
tone (JCS) Each distinguishable shade variation from black to white on imagery. HDBK-850
tone copy That material in which tones or shades of solid color appear. HDBK-850
tool A software component, sometimes called an application object, which can act as either a service provider or service requester within an application platform. OpenGIS Guide
topic compendium with free-text summary A topic compendium supplemented by a free-text summary of the exploitation results that summarizes, integrates, or emphasizes significant intelligence results. USIS 95
topic report An account or analysis of imagery derived information pertaining to a single subject other than a specified target. USIS 2-1.1
topical map A map designed to portray a special subject; e.g., administrative subdivisions, railroads, telecommunications, power lines, navigable waterways. Also called special-subject map; thematic map. HDBK-850
topoangulator An instrument used to measure vertical angles in the principal plane of an oblique photograph. HDBK-850
topocentric Of measurements or coordinates, referred to the position of the observer on the Earth as the origin. HDBK-850
topocentric coordinates Coordinates whose origin is on the Earth's surface as distinguished from geocentric coordinates whose origin is at the center of the Earth. HDBK-850
topocentric equatorial coordinates A coordinate system centered at the observer's position on the surface of the Earth with one coordinate plane parallel to the Equator and one axis parallel to the north polar axis of the Earth. HDBK-850
topocentric horizon See apparent horizon. HDBK-850
topographic base film An aerial photographic film with a dimensionally stable base used primarily for mapping. HDBK-850
topographic correction See terrain correction. HDBK-850
topographic deflection That part of the deflection of the plumb line which is caused by the gravitational pull exerted by topographic masses. Topographic deflection is not the same as deflection of the plumb line or station error, but is the theoretical effect produced by the resultant gravitational pull of the unevenly distributed topographic masses around the station, no allowance being made for isostatic compensation. Also called indirect effect on the deflections. HDBK-850
Topographic Engineering Center (TEC) See United States Army Topographic Engineering Center (USATEC). HDBK-850
topographic expression The effect achieved by shaping and spacing contour lines so that topographic features can be interpreted with ease and fidelity. Good expression is achieved by delineating the contours in appropriate relationship to each other, with due consideration given to the scale and contour interval of the map. Also called configuration of terrain. See also topography. HDBK-850
topographic feature See topography, definition 1. HDBK-850
topographic map (JCS) A map which presents the vertical position of features in measurable form as well as their horizontal positions. See also map. HDBK-850
Topographic Map of the United States The recommended designation for the topographic map of the United States being prepared of quadrangle areas in atlas sheet form, chiefly by the U.S. Geological Survey. This map portrays all basic information about location, elevation, and extent of physical and cultural features that are required for preliminary economic and engineering studies, and for incorporation in a base for maps prepared for special purposes. HDBK-850
topographic plot Representation, by means of contour lines, of the ground relief of an area, shown in a stereoscopic model. See also compilation, definition 2. HDBK-850
topographic survey A survey which has for its major purposes the determination of the relief of the surface of the Earth and the location of natural and man-made features thereon. HDBK-850
topographical latitude See geodetic latitude. HDBK-850
topography 1. The configuration of the surface of the Earth, including its relief, the position of its streams, roads, cities, etc. The Earth's natural and physical features collectively. A single feature such as a mountain or valley is termed a topographic feature. Topography is subdivided into hypsography (the relief features), hydrography (the water and drainage features), culture (man-made features), and vegetation. 2. The science of delineation of natural and man-made features of a place or region especially in a way to show their positions and elevations. The term includes the scientific and technical fields of surveying, geodesy, geophysics, military geography, photogrammetry, cartography, graphic arts, and related activities to the extent that they are essential to the accomplishment of the military mapping, geodesy, and military geographic intelligence mission. 3. In oceanography, the term is applied to a surface such as the sea bottom or a surface of given characteristics within the water mass. HDBK-850
topologic error checking The process of ensuring that the logical consistency of the data is intact, that is, all polygons are closed, all arcs are connected to nodes, etc. HDBK-850
topological Properties of geometric figures as adjacency that are not altered by distortion as long as the surface is not torn. HDBK-850
topological concepts Properties of geometric figures that do not change under continuous (smooth) transformation; such as, is connected to, is inside of, is disconnected, has three connected parts (none connected to any other), is a point on the boundary of, is on the left of, is a node where five segments meet, etc. HDBK-850
topological data base A data base that employs the concepts of topology to indicate the relationships of cartographic features, geometrically expressed as points, lines, and polygons. Commonly employed as the basis for data bases to be used in geographic information systems. HDBK-850
topological data structure A vector data structure which has the same characteristics as the chain-node data structure, but also establishes the topological relationships (connectivity, adjacency, and inclusion) between features in a vector data set. HDBK-850
topological entities A collection of objects (i.e., nodes, edges and faces) used to define the spatial relationships among the features of the Earth's surface. HDBK-850
topological relationship Tthe geometric association between geographic features that remains unaffected by changes in shape and size. ISO/TC 211
topological relationships How data elements relate to each other within the data base. In particular, how a change to one element affects other elements. HDBK-850
topological structuring The process of organizing data topologically so that the relationships and reference linkages are specified. HDBK-850
topological verification The process of verifying the topological relationship between data elements. HDBK-850
Topologically Integrated Geographic and Resource Information System (TIGRIS) An object oriented geographic information system with a consolidated data structure. Developed by Intergraph Corporation. HDBK-850
Topologically Integrated Geographic Encoding and Referencing (TIGER® ) file The TIGER/Line files are a digital database of geographic features, such as roads, railroads, rivers, lakes, political boundaries, census statistical boundaries, etc. covering the entire United States. The data base contains information about these features such as their location in latitude and longitude, the name, the type of feature, address ranges for most streets, the geographic relationship to other features, and other related information. They are the public product created from the United States Census Bureau's TIGER data base of geographic information. TIGER was developed at the Census Bureau to support the mapping and related geographic activities required by the decennial census and sample survey programs. These files are not graphic images of maps, but rather digital data describing geographic features. To make use of these data, a user must have mapping or Geographic Information System (GIS) software that can import TIGER/Line data. With the appropriate software a user can produce maps ranging in detail from a neighborhood street map to a map of the United States. Census Web Site
topology The way in which geographical elements are linked together, including the spatial relationships existing among geographic features and the methods used within the computer environment to geometrically depict, store, and examine the data within this relational context. Topology includes adjacency, inclusion, and connectivity. See also adjacency; connectivity; inclusion. HDBK-850
topology The scientific explanation of the relationship between connected or adjacent points, lines, and areas; specifically properties of objects that remain invariant under transformation by continuous mapping . ISO/TC 211
topology Properties of geometric forms that remain invariant when the forms are deformed or transformed by bending, stretching, and shrinking. Among the topological properties of concern in GIS are connectivity, order, and neighborhood. OpenGIS Guide
toponym A name applied to a natural or cultural feature. For U.S. Government usage, policies and decisions governing place names on Earth are established by the United States Board on Geographic Names. Also called geographic name and place name. See also descriptive name. HDBK-850
toponymy 1. The study and treatment of toponyms. 2. A body of toponyms. HDBK-850
topple The vertical component of precession or wander, or the algebraic sum of the two. HDBK-850
topple axis That horizontal axis, perpendicular to the (horizontal) spin axis of a gyroscope, around which topple occurs. HDBK-850
torsion balance A device for measuring combinations of the second derivatives of the gravity potential, which are closely related to the horizontal components of the deflection of the vertical. It consists of a bar suspended horizontally by an elastic filament, one end of the bar being subjected to the influence of the attracting force to a greater degree than the other end. The attracting force is balanced and its comparative strength measured by the torsional reaction of the filament. HDBK-850
total departures See abscissa. HDBK-850
total drift The algebraic sum of drift due to precession and that due to wander. Also called drift. HDBK-850
total latitudes See ordinates. HDBK-850
total magnetic intensity The vector resultant of the intensity of the horizontal and vertical components of the Earth's magnetic field at a specified point. HDBK-850
Total Package Fielding (TPF) The method of fielding a new system, a system upgrade, or hardware providing improved reliability or extended capability. TPF involves the fielding of all the parts, tools, test equipment, and documentation, along with the system hardware and software. It includes the integrated scheduling of all facility modifications and training with the fielding plan and the full coordination of the entire fielding schedule and process with the user and the O & M activity. [DISA/D4] DISA CFS
total station instrument A survey instrument capable of measuring delta x, y, and z components without significant alterations. HDBK-850
Touch Interactive Display (TID) Use of a physical device between the user and the display which acts as the input mechanism. [HCI Style Guide] DISA CFS
touch plate See kiss plate. HDBK-850
touchscreen A device/technology that enables a user to touch a computer monitor to make a selection. Typically used in a kiosk. Multimedia
town plan inset See inset. HDBK-850
town site survey The marking of lines and corners within one or more regular units of the township subdivision by which the land is divided into blocks, streets, and alleys as a basis for the disposal of title in parcels of land. HDBK-850
township The unit of survey of the public lands; normally a quadrangle approximately 6 miles on a side with boundaries conforming to meridians and parallels within established limits, containing thirty-six sections, some of which are designed to correct for the convergence of meridians or range lines. See also fractional township. HDBK-850
township corner A corner of a township. See also closing township corner. HDBK-850
township lines The township boundaries that run north and south are termed range lines; with few exceptions the range lines are run on cardinal and have been intended to be on cardinal. The boundaries running east and west are termed township lines. By law, they were intended to be on true parallels of latitude. HDBK-850
trace See selection overlay. HDBK-850
track (JCS) The actual path of an aircraft above, or a ship on the surface of the Earth. The course is the path which is planned; the track is the path which is actually taken. HDBK-850
track adjustment Adjustment to a ship's track resulting from set and drift of the vessel. HDBK-850
track chart A chart showing recommended, required, or established tracks, and usually indicating turning points, courses, and distances. HDBK-850
tracking camera See ballistic camera. HDBK-850
tracking station A ground-based complex set up to track an object moving through the atmosphere or space, by visual, photographic, photoelectric, or electronic methods. HDBK-850
trader A kind of intermediary service which acquires services from one or more providers for "resale" to a service requester. The trader service insulates requester and provider services from having to interact directly with one another. The trader is responsible to the requester for all aspects of the requested service. OpenGIS Guide
Trading Partner Agreement (TPA) Agreement between the government and a trading partner that defines general EDI [Electronic Data Interchange] procedures, term and conditions, and the EDI transaction sets that will be used. [DISA/D2] DISA CFS
traffic separation schemes Portrayal on nautical charts of schemes aimed at reducing the risk of collision in congested and/or converging areas by separating traffic moving in opposite, or nearly opposite, directions. HDBK-850
traffic-circulation map (JCS) A map showing traffic routes and the measures for traffic regulation. It indicates the roads for use of certain classes of traffic the location of traffic control stations, and the directions in which traffic may move. Also called circulation map. See also map. HDBK-850
training executive agent The training authority identified by the Community Imagery Training Committee on behalf of the Director, CIO [NIMA], and formally designated by the Office of the Secretary of Defense and the Director, Central Intelligence to conduct inter service and interagency training as a service of common concern for a specific imagery discipline. USIS 95
Training Management Plan (TMP) The TMP is government generated documentation associated with an acquisition program that provides for a systematic process for determining training requirements, identifying those responsible for training development and funding, and developing training strategy for the life cycle of the program. NIMC
trajectory In general, the curve that a body describes in space. An orbit is a trajectory which does not intersect the Earth. HDBK-850
transaction A set of related operations that result in the update of data. CEN/TC 287
transaction A unit of work consisting of an arbitrary number of individual operations all of which will either complete successfully or abort with no effect on the intended resources. A transaction has well defined boundaries. A transaction starts with a request from the application program and either completes successfully (commits) or has no effect (abort). Both the commit and abort signify a transaction completion. IEEE P1003.0
Transaction Transparency A distribution transparency which masks coordination of activities amongst a configuration of objects to achieve consistency. RM-ODP
transcriber See point-transfer device. HDBK-850
transcription 1. The process of recording the sounds and/or grammatical elements of a language in terms of a specific writing system. 2. An item of a language which has undergone this process. HDBK-850
transducer Any device for converting energy from one form to another (electrical, mechanical, or acoustic). In sonar, it usually combines the functions of a hydrophone and a projector. HDBK-850
transfer schema A conceptual schema for rules and operators for transferring geographic data and metadata. CEN/TC 287
transfer standard A set of formats and protocols used to move data from one system to another without loss. May be defined at the logical level, the physical level, or both. HDBK-850
transformation 1. (photogrammetry) The process of projecting a photograph (mathematically, graphically, or photographically) from its plane onto another plane by translation, rotation, and/or scale change. The projection is made onto a plane determined by the angular relations of the camera axes and not necessarily onto a horizontal plane. See also rectification. 2. (surveying) The computational process of converting a position from UTM or other grid coordinates to geodetic, and vice versa; from one datum and ellipsoid to another using datum shift constants and ellipsoid parameters. The survey position of a point is frequently given in several different grids or ellipsoids; local datum and Doppler-derived WGS 84 are common requirements. HDBK-850
transformation schema A conceptual schema defining rules and operators for changing the form of data from one syntax and/or method of representation to another. CEN/TC 287
transformed print A photographic print made by projection in a transforming printer. HDBK-850
transforming printer A specially designed projection printer of fixed geometry used for transforming the oblique components of a coupled camera installation, a multiple-lens camera, or a panoramic camera onto a plane perpendicular to the axis of the system. See also rectifier; universal transforming printer. HDBK-850
transient object An object whose existence is limited by the lifetime of the process or thread that created it. CORBA 2.2
transit 1. The apparent passage of a star or other celestial body across a defined line of the celestial sphere, as a meridian, prime vertical, or almucantar. The apparent passage of a star or other celestial body across a line in the reticle of a telescope, or some line of sight. The apparent passage of a smaller celestial body across the disk of a larger celestial body. The transit of a star across the meridian occurs at the moment of its culmination, and the two terms are sometimes used as having identical meanings; such usage is not correct, even where the instrument is in perfect adjustment. At the poles, a star may have no culmination but it will transit the meridians. See also culmination; lower transit; meridian transit; upper transit. 2. A surveying instrument composed of a horizontal circle graduated in circular measure and an alidade with a telescope which can be reversed in its supports without being lifted therefrom. See also theodolite. 3. The act of reversing the direction of a telescope by rotation around its horizontal axis. Also called plunge; inverting; telescoping. 4. An astronomic instrument having a telescope which can be so adjusted in position that the line of sight may be made to define a vertical circle. Also called astronomic transit. See also broken telescope transit; solar transit. HDBK-850
transit instrument See transit, definition 4. HDBK-850
transit line Any line of a traverse which is projected, either with or without measurement, by the use of a transit or other device. It is not necessarily an actual line of final survey but may be an accessory line. Also called traverse line. HDBK-850
transit micrometer A form of registering micrometer with its movable wire placed in the focal plane of an astronomic transit and at right angles to the direction of motion of the image of a star which is observed at or near culmination. Also called impersonal micrometer, because it almost completely eliminates the effect of the personal equation on time observations made with it. HDBK-850
transit micrometer contact correction A quantity applied to the chronograph record of a star transit observed with the aid of a transit micrometer to allow for the time required for the contact spring to cross one-half of the width of a contact strip in the head of the micrometer. HDBK-850
transit rule A method of balancing a survey. Corrections corresponding to the closing errors in latitude and departure are distributed according to the proportion: latitude and departure of each line of the traverse to the arithmetical sums of the latitudes and departures of the entire traverse. The transit rule is used when it is assumed that the closing errors are due less to the errors in the observed angles than to errors in the measured distances. HDBK-850
transit traverse A survey traverse in which the angles are measured with an engineer's transit or theodolite and the lengths with a metal tape. A transit traverse is usually executed for the control of local surveys and is of second-order or third-order quality. HDBK-850
transit-and-stadia survey A survey in which horizontal and vertical directions or angles are observed with a transit and distances are measured by transit and stadia. HDBK-850
transition curve See spiral curve. HDBK-850
translation 1. The process of rendering oral or written text of one language in terms of text of corresponding meaning of another language. See also romanization transcription; transliteration. 2. Movement in a straight line without rotation. HDBK-850
translation The process of converting data or commands from one computer format to another, or from one computer language to another. OpenGIS Guide
translational movement The systematic movement of projector assemblies in line-of-flight directions in a stereoplotting instrument. HDBK-850
transliteration 1. The process of recording the graphic symbols of one writing system in terms of corresponding graphic symbols of a second writing system. 2. An item of a language which has undergone this process. HDBK-850
translocation The determination of the relative position between two points from simultaneous Doppler satellite observations. HDBK-850
translunar Outside the Moon's orbit about the Earth. See also cislunar. HDBK-850
translunar space As seen from the Earth at any moment, space lying beyond the orbit of the Moon. HDBK-850
translunar trajectory A trajectory extending outside the Moon's orbit about the Earth. HDBK-850
transmission (optics) The ratio of transmitted light to the incident light. If 100 units of light fall upon a translucent material and 10 of them succeed in passing through, then it can be said that the material has 1/10 or 10 percent transmission. HDBK-850
transparency (JCS) An image fixed on a clear base by means of a photographic, printing, chemical, or other process, especially adaptable for viewing by transmitted light. See also diapositive. HDBK-850
transparency The ability of systems or components of systems to hide the details of their implementations from other client or server systems or components of systems. OpenGIS Guide
transparency The property of hiding from a particular user the potential behavior of some parts of the system. RM-ODP
transponder (JCS) A receiver-transmitter which will generate a reply signal upon proper interrogation. See also responsor. HDBK-850
transport layer The fourth layer of the Open Systems Interconnect (OSI) Reference Model that provides an end-to-end control for information interchange at the reliability and quality level required for the upper three layers (5 to 7). Layer 4 includes such functions as multiplexing and segmenting data into appropriately sized units for handling by the network layer and provides a level of isolation designed to keep the user independent of the physical and operational functions of the network itself. [DISA/D2] DISA CFS
transverse In cartography, pertaining to or measured on a map projection in which a meridian is used as a fictitious equator. Also called inverse. HDBK-850
transverse axis The distance between the apsides. It is identical to the semimajor axis for elliptical orbits. HDBK-850
transverse chart A chart on a transverse projection. Also called inverse chart. HDBK-850
transverse cylindrical orthomorphic chart (TCOC) See transverse Mercator chart. HDBK-850
transverse cylindrical orthomorphic map projection See transverse Mercator map projection. HDBK-850
transverse equator The plane which is perpendicular to the axis of a transverse projection. Also called inverse equator. HDBK-850
transverse graticule A fictitious graticule based upon a transverse projection. See also fictitious graticule. HDBK-850
transverse latitude Angular distance from a transverse equator. Also called inverse latitude. See also fictitious latitude. HDBK-850
transverse longitude Angular distance between a prime transverse meridian and any given transverse meridian. Also called inverse longitude. See also fictitious longitude. HDBK-850
transverse map projection A map projection in which the projection axis is rotated 90 in azimuth. HDBK-850
transverse Mercator chart A chart on the transverse Mercator projection. Also called inverse cylindrical orthomorphic chart; inverse Mercator chart; transverse cylindrical orthomorphic chart. HDBK-850
transverse Mercator grid An informal designation for a state coordinate system based on a transverse Mercator map projection. Also called Gauss-Kruger grid. HDBK-850
transverse Mercator map projection A conformal cylindrical map projection, being in principle equivalent to the regular Mercator map projection turned (transversed) 90 in azimuth. In this projection, the central meridian is represented by a straight line, corresponding to the line which represents the Equator on the regular Mercator map projection. Neither the geographic meridians (except the central meridian) nor the geodetic parallels (except the Equator) are represented by straight lines. Also called inverse cylindrical orthomorphic map projection; inverse Mercator map projection; transverse cylindrical orthomorphic map projection. HDBK-850
transverse meridian A great circle perpendicular to a transverse equator. The reference transverse meridian is called prime transverse meridian. Also called inverse meridian. See also fictitious meridian. HDBK-850
transverse model datum See model datum, definition 1. HDBK-850
transverse parallel A circle or line parallel to a transverse equator, connecting all points of equal transverse latitude. Also called inverse parallel. See also fictitious parallel. HDBK-850
transverse pole One of the two points 90 from a transverse equator. HDBK-850
transverse polyconic map projection A polyconic map projection which is turned (transversed) 90 in azimuth by substituting for the central meridian, a great circle perpendicular to the geographic meridian to provide a control axis for the projection, along which axis will lie the centers of the circular arcs representing lines of tangency of cones with the surface of the sphere. HDBK-850
transverse position A split camera installation so positioned that the plane containing the camera axis is perpendicular to the line of flight. HDBK-850
transverse rhumb line A line making the same oblique angle with all fictitious meridians of a transverse Mercator projection. Transverse parallels and meridians may be considered special cases of the transverse rhumb line. Also called inverse rhumb line. See also fictitious rhumb line. HDBK-850
traverse (JCS) A method of surveying in which lengths and directions of lines between points on the Earth are obtained by or from field measurements, and used in determining positions of the points. [A survey traverse may determine the relative positions of the points which it connects in series, and if tied to control stations on an adopted datum, the positions may be referred to that datum. Survey traverses are classified and identified in a variety of ways: according to methods used, as astronomic traverse; according to quality of results, as first-order traverse; according to purpose served, as geographical exploration traverse; and according to form, as closed traverse, etc.] See also angle-to-right traverse; azimuth traverse; closed traverse; connecting traverse; deflection angle traverse; first-order traverse; fourth-order traverse; geographical exploration traverse; interior angle traverse; loop traverse; open traverse; phototrig traverse; planetable traverse; random traverse; second-order traverse: spur traverse; stadia traverse; subtense bar traverse; subtense base traverse; third-order traverse; transit traverse. HDBK-850
traverse adjustment See balancing a survey. HDBK-850
traverse angle Measurement of the horizontal angle from a preceding adjacent station to the following adjacent station. HDBK-850
traverse error of closure See error of closure, definition 8. HDBK-850
traverse line See transit line. HDBK-850
traverse net See survey net, definition 1. HDBK-850
traverse station A point on a traverse over which an instrument is placed (a setup). Also, on a traverse, a length of 100 feet measured on a given line, either straight, broken, or curved. HDBK-850
traverse tables Mathematical tables listing the lengths of the sides opposite the oblique angles for each of a series of right-angle plane triangles as functions of the length and azimuth (or bearing) of the hypotenuse. HDBK-850
traverse the instrument To rotate a survey instrument about its vertical axis; that is, turning the instrument in azimuth. HDBK-850
triangle See astronomic triangle; celestial triangle; navigational triangle; preliminary triangle; spherical triangle; spheroidal triangle; terrestrial triangle. HDBK-850
triangle closure See error of closure, definition 7. HDBK-850
triangle error of closure See error of closure, definition 7. HDBK-850
triangle of doubt In a simple two-point problem, the triangle resulting when the check ray fails to pass through the point of intersection of the two intersecting rays. HDBK-850
triangle of error The triangle formed when three plotted rays fail to intersect perfectly. The center of the triangle may be considered to be the adjusted position. See also resection. HDBK-850
triangle-of-error method In surveying, a technique for solving the three-point problem graphically by a triangle of error. These methods are generally referred to by name, such as Bessel's method, Coast-Survey method, and Lehmann's method, each of which is based upon its own factors. See also triangle of error. HDBK-850
triangulated irregular network (TIN) A terrain model created from continuously connected triangles derived from the Delauney algorithm. The vertices of the triangles form irregularly spaced elevation posts. Unlike a grid, the TIN allows extra information to be displayed in areas of complex relief without displaying dense or redundant data gathered in areas of simple relief. HDBK-850
triangulation A method of surveying in which the stations are points on the ground which are located at the vertices of a chain or network of triangles. The angles of the triangles are measured instrumentally and the sides are derived by computation from selected sides which are termed base lines, the lengths of which are obtained from direct measurements on the ground. See also analytical three-point resection radial triangulation; arc triangulation; area triangulation; base net; direct radial triangulation; first-order triangulation; flare triangulation; graphical radial triangulation; hand-templet triangulation; isocenter triangulation; mechanical-templet triangulation; nadir-point triangulation; phototriangulation; radial triangulation; satellite triangulation; second-order triangulation; semianalytical triangulation; ship-to-shore triangulation; slotted-templet triangulation; spider-templet triangulation; third-order triangulation; trilateration. HDBK-850
triangulation base line See base line. HDBK-850
triangulation net See survey net, definition 1. HDBK-850
triangulation reconnaissance A preliminary survey to select the location of stations to give the most feasible triangulation scheme. HDBK-850
triangulation signal A rigid structure erected over or close to a triangulation station and used for supporting an instrument and observer, or target, or instrument and observer and target, in a triangulation survey. Also, any object, natural or artificial, whose position is obtained in a triangulation survey. The term may be applied to a structure whose position is determined by triangulation, but whose primary purpose is to serve later in a hydrographic or topographic survey, when it may become known as a hydrographic or topographic signal. HDBK-850
triangulation station (JCS) A point on the Earth whose position is determined by triangulation. Also called trig point. HDBK-850
triangulation system The main scheme, or net, of primary stations and the auxiliary stations. The main scheme is the framework of the system and is tied at several points to previously established triangulation stations of equal or higher order. See also survey net, definition 1. HDBK-850
triangulation theodolite See direction instrument theodolite. HDBK-850
triangulation tower A structure used to elevate the line of sight above intervening obstacles. Usually consists of two independent structures, one within the other; the center structure supports the theodolite and the outer structure supports the observer and the signal. See also Bilby steel tower. HDBK-850
triaxial ellipsoid An ellipsoid having three unequal axes, the shortest being its polar axis, while the two longer ones lie in the plane of its equator. HDBK-850
tricamera photography (JCS) Photo-graphy obtained by simultaneous exposure of three cameras systematically disposed in the air vehicle at fixed overlapping angles relative to each other in order to cover a wide field. See also fan camera photography. HDBK-850
tridimensional datum A datum which serves as a reference for defining 3-dimensional coordinates. EXAMPLE: geocentric ellipsoidal datum for defining f,l,h, geocentric cartesian datum for defining X,Y,Z, local datum for defining u,v,w. CEN/TC 287
trig control See field control. HDBK-850
trig dossier A detailed record on the triangulation of an area, giving the coordinates of the triangulation stations. HDBK-850
trig list (JCS) A list published by certain Army units which includes essential information of accurately located survey points. [A publication containing all available positional data and elevations with the respective descriptions of horizontal and/or vertical control points, usually arranged according to the location of the control points within the limits of map sheets of large-scale series.] HDBK-850
trig point See triangulation station. HDBK-850
trigonometric leveling The determination of differences of elevations from observed vertical angles combined with Iengths of lines. A type of indirect leveling. HDBK-850
trilateration A method of surveying wherein the lengths of the triangle sides are measured, usually by electronic methods, and the angles are computed from the measured lengths. See also triangulation. HDBK-850
trilateration net A network of points whose positions relative to one another are determined by measurement and adjustment of the length of the sides of the triangles formed by these points. HDBK-850
trilinear surveying The determination of the position of a point of observation by measuring the angles at that point between lines to three points of known position. See also resection. HDBK-850
trim marks Lines placed on original copy to serve as guides in cutting or trimming the printed sheets to their prescribed size. HDBK-850
trim size (JCS) The size of a map or chart sheet when the excess paper outside the margin has been trimmed off after printing. HDBK-850
trimetrogon camera A triple camera assembly with one vertical and two fixed-angle obliques whose imagery overlapped the vertical and with all three axes lying in a plane perpendicular to the line of flight. Most camera assemblies of this design were referred to as trimetrogon camera because of the widespread usage of the Metrogon lens in early tricamera photography. HDBK-850
trimetrogon photography See fan camera photography. HDBK-850
trimming and mounting diagram A sketch showing how the prints of a transformed multiple-lens photograph should be corrected to obtain, in effect, a photograph made by a single lens. The information is given in the form of distances referred to the fiducial marks on the photograph, and is the result of the calibration test for the particular camera used. HDBK-850
Tri-Service Tactical Communication A tactical switch communications system for support of all U.S. Services. The system has six different interface terminals to accommodate the gradual transition to a fully digital and automatic system. USIS 95
TROJAN SPIRIT An Army Special Purpose Integrated Remote Intelligence Terminal (SPIRIT) that transfers data, text, and secondary imagery worldwide and has a secure voice capability. USIS 95
Tropic of Cancer The northern parallel of declination, approximately 2327' from the celestial equator, reached by the Sun at its maximum declination, or the corresponding parallel on the Earth. HDBK-850
Tropic of Capricorn The southern parallel of declination, approximately 2327' from the celestial equator, reached by the Sun at its maximum declination, or the corresponding parallel on the Earth. HDBK-850
tropical month The average period of the revolution of the Moon about the Earth with respect to the vernal equinox, approximately 27 1/3 days. HDBK-850
tropical year The interval of time between two successive passages of the vernal equinox by the Sun. The tropical year is the year of the seasons, and the basis of the conventional calendar year. Also called astronomic year; equinoctial year; natural year; solar year. HDBK-850
tropopause (JCS) The transition zone between the stratosphere and the troposphere. The tropopause normally occurs at an altitude of about 25,000 to 45,000 feet in polar and temperate zones, and at 55,000 feet in the tropics. See also atmosphere. HDBK-850
troposphere (JCS) The lower layers of atmosphere, in which the change of temperature with height is relatively large. It is the region where clouds form, convection is active, and mixing is continuous and more or less complete. See also atmosphere. HDBK-850
tropospheric scatter (JCS) The propagation of radio waves by scattering as a result of irregularities or discontinuities in the physical properties of the troposphere. HDBK-850
trough compass See declinatoire. HDBK-850
Troughton level An English instrument having the spirit level permanently attached to the top of the telescope tube HDBK-850
true 1. Related to true north as opposed to magnetic north. 2. Actual, as contrasted with fictitious, as true Sun. 3. Related to a fixed point, either on the Earth or in space, as true wind; in contrast with relative, which is related to a moving point. 4. Corrected, as true altitude. 5. One of two alternate values (True/False) used in Boolean logic. HDBK-850
true altitude 1. (JCS) The height of an aircraft as measured from mean sea Ievel. 2. The actual altitude of a celestial body above the celestial horizon. Also called observed altitude. HDBK-850
true amplitude Amplitude relative to true east or west. See also amplitude. HDBK-850
true anomaly See anomaly, definition 3. HDBK-850
true azimuth The horizontal direction of any line measured clockwise from true north. HDBK-850
true bearing The horizontal angle between the meridian line and a line on the Earth. The term true bearing is used in many of the early descriptions of land boundaries in the United States. It is associated with true north, referring to the direction of the north point as determined by astronomic observations. If an astronomically determined bearing is used, however, the term astronomic bearing is preferred over true bearing. HDBK-850
true depression angle The setting of the oblique cameras in the photographic aircraft with relation to the true horizon. It is defined by a ray from the exposure station through the principal point of the oblique photograph and a ray to the true horizon. HDBK-850
true direction horizontal direction expressed as angular distance from true north. HDBK-850
true error See resultant error. HDBK-850
true horizon (JCS) 1. The boundary of a horizontal plane passing through a point of vision. 2. In photogrammetry, the boundary of a horizontal plane passing through the perspective center of a lens system. See also horizon trace. HDBK-850
true line A line of constant bearing (rhumb line) between two corners of a survey. HDBK-850
true meridian A term used to distinguish the great circle through the geographical poles from magnetic meridian, compass meridian, or grid meridian. HDBK-850
true north (JCS) The direction from an observer's position to the geographical North Pole. The north direction of any geographic meridian. [The term was originally applied to astronomic north to distinguish it from magnetic north.] HDBK-850
true place See true position. HDBK-850
true position The position of a celestial body after all known corrections including precession and nutation have been made. Also called true place. HDBK-850
true prime vertical The vertical circle through the true east and west points of the horizon, as distinguished from magnetic or grid prime vertical through the magnetic or grid east and west points, respectively. HDBK-850
true sidereal time See apparent sidereal time. HDBK-850
true solar time See apparent solar time. HDBK-850
true sun See apparent sun. HDBK-850
true value That value of quantity which is completely free from errors. Since the errors to which physical measurements are subject cannot be known exactly, it follows that the true value of a quantity cannot be known with exactness. In survey work, the most probable value is used as best representing the true value of the quantity. HDBK-850
true-to-scale A condition where map measurements are in exact agreement with the stated map scale. Since all map projections involve some scale change, the scale is not true at all places on a map. HDBK-850
trunk A circuit connecting two switching facilities; a communications medium (single or multichannel) between two successive terminals where channels may be tested, rerouted, dropped out, or switched to another route. [Joint Pub 6-02.1] DISA CFS
tuple An ordered set. Such as a set of coordinates that define a point. See also coordinate tuple. OpenGIS Guide
turning point (TP) A point on which both a minus sight (foresight) and a plus sight (backsight) are taken on a line of direct levels. Also, in topographic surveys, any point on which the rod is held while the instrument is moved to another station. These turing points are often marked for future use as tie or check points. HDBK-850
turning point pin A steel pin about one foot long. In leveling operations, the turning point is driven into the ground where it is necessary to establish a point that will be stable in elevation for a short period of time. When it has served its usefulness at one point, it is removed and carried by the rodman for subsequent reuse. HDBK-850
turret graver A scribing instrument which permits the use of points of several weights interchangeably without the inconvenience of interrupting the scribing to replace points. The turret head is revolved to position the desired point, and scribing is resumed. HDBK-850
tusche An ink for drafting printing areas on lithographic plates. HDBK-850
tusching The operation of adding work to the image on a press plate, correcting lines and lettering, and adding solids by means of tusche. Also called lithographic drafting. HDBK-850
Twelfth Air Force (12AF) Twelfth Air Force is a major component command of United States Southern Command (USSOUTHCOM). Twelfth Air Force's mission is to employ decisive air power through effective command and control in support of USSOUTHCOM and Commander In Chief (CINC) worldwide. Twelfth Air Force is headquartered at Davis-Monthan AFB, AZ. 12AF Web Site
two-base method A technique of barometric leveling utilizing three barometers. Two barometers, one high established over a known elevation, and one low established over a known elevation, and a roving barometer operating between the two known positions. High and low barometers are read and recorded, with temperature, every five minutes. The roving barometer and temperature are read and recorded at each station occupied. Data are reduced to position and elevation by office computation. The only barometric Ieveling method able to consistently produce errors less than 1 meter. See also fly-by-method; loapfrog method. HDBK-850
two-body orbit The motion of a point mass in the presence of the gravitational attraction, of another point mass, and in the absence of any other forces. This orbit is usually an ellipse, but may be a parabola or hyperbola. HDBK-850
two-body problem That problem in celestial mechanics which treats of the relative motion or of two-point masses under their mutual gravitional attraction. HDBK-850
two-dimensional (2-D) data Areal data in two dimension, such as northing-easting or latitude-longitude. HDBK-850
two-dimensional (2-D) pantograph In relief model making, a machine permitting the cutting, at a predetermined scale, of the three-dimensional terrain base from the flat map contour drawing HDBK-850
two-point problem A problem in determining the position of a point with the known factor being the length of one line that does not include the point to be located. HDBK-850
two-step enlargement/reduction A technique of projecting and printing a small image; then copying and projecting it again to the required size. This is often necessary when copy size/copy camera limitations do not permit enlargement or reduction in a single operation. HDBK-850
two-transit method A method of ship-to-shore triangulation whereby the position of the sounding boat or pole is determined by angle observations from two transits on shore set up over points previously positioned. HDBK-850
type In printing (typography) a metal block having a raised letter or figure which, when inked, is used to make an impression on paper or other material. Type can also be in the form of negative or positive stripping film. Categories of type include hand-set cold type; hot type, such as Linotype; Monotype (punched tape to metal); phototype (film negative or positive); and Photontype (tape to film). Type is identified by its style and size. HDBK-850
type A predicate characterizing a collection of entities. An entity is of the type (or satisfies the type) if the predicate holds for that entity. Types are needed (at least) objects, interfaces, and actions. An entity may have several types and may acquire and lose types (for example: person, employee, homeowner). RM-ODP
typography The art of type composition and printing from raised type surfaces. HDBK-850

Last Updated by Mark Owens 7 January 1999.