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Term Definition/Description Source
Earth fixed coordinate system Any coordinate system in which the axes are stationary with respect to the Earth. HDBK-850
Earth inductor An instrument designed for use in magnetic surveys to determine magnetic dip. In principal, the instrument is a small dynamo by which the electrical flow can be introduced to the coil of the instrument. The presence or absence of current is indicated by a galvanometer which provides for direct reading of magnetic dip. HDBK-850
Earth inductor compass A compass depending for its indications upon the current generated in a coil revolving in the Earth's magnetic field. HDBK-850
Earth Model An approach to abstracting the Earth. The data model for the Earth. OpenGIS Guide
Earth Resources Observation Systems (EROS) Data Center (EDC) Besides collecting and distributing data from several series of satellites, the EDC archives more than 8 million photographs taken from airplanes. The EDC's huge and growing base of earth science information - the world's largest - is used by scientists at the EDC itself, within the private sector, and at government institutions and universities around the globe. By law, the EDC is home to the National Satellite Land Remote Sensing Data Archive, an immense storehouse of information on land-surface phenomena, now dating back three decades. In recent years the EDC also has become the distributed active archive center (DAAC) for land processes on behalf of the National Aeronautics and Space Administration's (NASA's) Mission to Planet Earth. The EDC also is designated a World Data Center - one of a global system of centers that have agreed to hold and share Earth observational data in compliance with international data exchange standards. The EDC is a component of the United States Geological Survey (USGS) and is located near Sioux Falls, SD. EDC Web Site
Earth Resources Technology Satellites ERTS was the original name for the LANDSAT program, from July 1972 to Jan 1975. USIS 95
Earth satellite A body that orbits about the Earth; specifically, an artificial satellite placed in orbit. HDBK-850
Earth tide A periodic movement of the Earth's crust caused by tide-producing forces of the Moon and Sun. HDBK-850
Earth-centered ellipsoid A reference ellipsoid whose geometric center coincides with the Earth's center of gravity and whose semiminor axis coincides with the Earth's rotational axis. HDBK-850
easement curve See spiral curve. HDBK-850
east point See prime vertical plane. HDBK-850
Eastern Missile Test Range Located at Cape Canaveral Air Force Station, FL. Responsible for launching of missiles and the space transportation system (shuttle). USIS 95
easting 1. (grid) Eastward (that is left to right) reading of grid values on a map. See also false easting. 2. (plane surveying) See departure, definition 1. HDBK-850
ebb tide The portion of the tide cycle between high water and the following low water. Also called falling tide. HDBK-850
eccentric Not having the same center. HDBK-850
eccentric anomaly See anomaly, definition 3. HDBK-850
eccentric error Centering error. HDBK-850
eccentric reduction (triangulation) The correction which must be applied to a direction observed by an instrument with either the instrument or signal (swing), or both, eccentric, to reduce the observed value to what it would have been if there had been no eccentricity. Also called eccentricity correction. HDBK-850
eccentric signal A signal (target) which is not in the same vertical line with the station which it represents. HDBK-850
eccentric station A survey point over which an instrument is centered and observations made, and which is not in the same vertical line with the station which it represents and to which the observations will be reduced before being combined with observations at other stations. Ln general, an eccentric station is established and occupied when it is impracticable to occupy the station center, or when it becomes necessary in order to see points which are not visible from the station center. HDBK-850
eccentricity 1. Amount of deviation from a center. See also eccentric station. 2. (surveyor's compass) An effect caused by one or a combination of the following conditions: (1) a straight line through the ends of the magnetic needle fails to pass through the center of rotation of the needle; (2) the center of rotation of the needle is not coincident with the center of figure of the graduated circle; (3) the line of sight fails to pass through the vertical axis of the instrument. 3. The ratio of the distances from any point of a conic section to a focus and the corresponding directrix. HDBK-850
eccentricity correction (triangulation) See eccentric reduction. HDBK-850
eccentricity of alidade The distance between the center of figure of the index points on an alidade and the center of figure of the graduated circle. See also eccentricity of instrument. HDBK-850
eccentricity of circle The distance between the center of figure of a graduated circle and its center of rotation. See also eccentricity of instrument. HDBK-850
eccentricity of ellipse The ratio of the distance between the center and a focus of an ellipse to the length of its semimajor axis. HDBK-850
eccentricity of instrument The combination of eccentricity of circle and eccentricity of alidade. HDBK-850
eccentricity of spheroid (ellipsoid) of revolution The eccentricity of an ellipse forming a meridian section of the spheroid. HDBK-850
echo See blip. HDBK-850
echo cancellation The process of reducing or eliminating sound originated at one end of a link, picked up by the far end microphone, and retransmitted to the originating end from being output to the speakers. Multimedia
echo sounder An echo sounding instrument used for depth measurements in water. HDBK-850
echo sounding A method for measuring depths by recording the time interval required for sound waves to go from a source of sound near the surface to the bottom and back again. HDBK-850
echo timing The measurement of time required for a short train of energy waves to travel the round trip path from an originating station to a reflector or transponder. HDBK-850
echogram A graphic record of depth measurements obtained by echo sounding equipment. Called fathogram when obtained from a Fathometer echo sounder. HDBK-850
eclipse 1. The reduction in visibility or disappearance of a nonluminous body by passing into the shadow cast by another nonluminous body. 2. The apparent cutting off, wholly or partially, of the light from a luminous body by a dark body coming between it and the observer. See also annular eclipse; lunar eclipse; solar eclipse. HDBK-850
eclipse year The interval between two successive conjunctions of the Sun with the same node of the Moon's orbit. HDBK-850
ecliptic The great circle formed by the intersection of the plane of the Earth's orbit around the Sun (or apparent orbit of the Sun around the Earth) and the celestial sphere. HDBK-850
ecliptic coordinate system See ecliptic system of coordinates. HDBK-850
ecliptic latitude See celestial latitude. HDBK-850
ecliptic longitude See celestial longitude. HDBK-850
ecliptic meridian A circle on the celestial sphere containing points of the same celestial longitude. HDBK-850
ecliptic node See node. HDBK-850
ecliptic parallel A circle on the celestial sphere containing points of the same celestial latitude. HDBK-850
ecliptic polar distance The complement of the celestial latitude. HDBK-850
ecliptic pole On the celestial sphere, either of the two points 90 from the ecliptic. HDBK-850
ecliptic system of coordinates A system of curvilinear celestial coordinates which uses the ecliptic as the primary reference plane and the ecliptic meridian through the vernal equinox as the secondary plane. The points 90 from the ecliptic are the north and south ecliptic poles. Angular distance north or south of the ecliptic analogous to latitude, is celestial latitude. Celestial longitude is measured eastward along the ecliptic from the vernal equinox through 360. HDBK-850
economic intelligence Intelligence regarding foreign economic resources, activities, and policies including the production, distribution, and consumption of goods and services, labor, finance, taxation, and other aspects of the international economic system. USIS 95
edge 1. (imagery) The boundary of an object in a photograph or image, usually characterized by a drastic change in the brightness value from the immediate interior of the boundary to the immediate exterior of the boundary. 2. (topology) A line used to represent the location of a linear feature and the borders of faces. Edges may be topologically linked to nodes, edges, and faces. HDBK-850
edge A 1-dimensional structure primitive being an oriented connection between two terminating nodes, which may be the same. ISO/TC 211
edge A one-dimentional primitive used to represent the location of a linear feature and/or the borders of faces. Depending upon the level of topology, edges may be topologically linked to nodes, edges, and faces. Edges are composed of an ordered collection of two or more coordinate tuples (pairs or triplets). At least two of the coordinate tuples must be distinct. The orientation of an edge can be recognized by the ordering of the coordinate tuples. VPF Glossary
edge enhancement The use of analytical techniques to emphasize edges in imagery. USIS 95
edge matching The comparison and graphic adjustment of features to obtain agreement along the edges of adjoining map sheets. HDBK-850
edge mating See matching. HDBK-850
editing The process of checking a map or chart in its various stages of preparation to insure accuracy, completeness, and correct preparation from and interpretation of the sources used, and to assure legible and precise reproduction. Edits are usually referred to by a particular production phase, such as compilation edit, scribing edit, etc. HDBK-850
effective area For any aerial photograph that is one of a series in a flight strip, that central part of the photograph delimited by the bisectors of overlaps with adjacent photographs. On a vertical photograph, all images within the effective area have less displacement than their conjugate images on adjacent photographs. HDBK-850
effective damage That damage necessary to render a target element inoperative, unserviceable, nonproductive, or uninhabitable. USIS 95
effective Earth radius See effective radius of the Earth. HDBK-850
effective focal length (EFL) See principal distance, definition 1. HDBK-850
effective radius of the Earth A fictitious value for the radius of the Earth, used in place of the geometrical radius to correct for atmospheric refraction when the index of refraction in the atmosphere changes linearly with height. HDBK-850
Egault level A French instrument having the spirit level attached to a level bar which also carries wyes in which the telescope rests. HDBK-850
electrical distance Length measured in terms of the distance traveled by radio waves in unit time. HDBK-850
electrical survey net adjuster (ESNA) A device used for obtaining least squares adjustments of level, traverse, and vertical angle nets through the medium of an analogous electrical net. HDBK-850
electromagnetic Radiation waves accelerated by electric charges that vary by frequency. USIS 95
electromagnetic pulse Electromagnetic radiation from a nuclear explosion caused by compton-recoil electrons and photoelectrons from photons. The resulting electric and magnetic fields may produce damaging current and voltage surges in electronic/electrical circuits. USIS 95
electromagnetic radiation Radiation made up of oscillating electric and magnetic fields and propagated with the speed of light. Includes gamma radiation, X-rays, ultraviolet, visible, infrared radiation, and radar and radio waves. USIS 95
electromagnetic spectrum The range of electromagnetic radiation in our known universe, which includes radio waves with large wavelengths to cosmic rays with small wavelengths. Freedman 1995
electronic bearing A bearing obtained by means of electronic equipment. HDBK-850
Electronic Bulletin Board (EBB) Bulletin board system that can be accessed with a modem for the purpose of exchanging information and acquiring files by downloading. For example, an agency can upload an request for quotation (RFQ) to be released to vendors who will be able to download at a specific time in order to respond to the RFQ. [DISA/D2] DISA CFS
Electronic Chart Display and Information System (ECDIS) A system which in its most complete design integrates all essential aids to navigation into one system including chart information, positional information and ships' parameters such as course and speed. Echosounder, readings, radar, complete or selective and other inputs may also be included. HDBK-850
Electronic Chart Update Manual (ECHUM) The electronic version of the Chart Update Manual (CHUM). See Chart Update Manual (CHUM). HDBK-850
Electronic Commerce (EC) End-to-end, paperless business environment that integrates electronic transfer and automated business system. [DISA/D2] DISA CFS
electronic control Control obtained by electronic devices. HDBK-850
electronic counter-countermeasure Division of electronic warfare involving actions taken to ensure friendly effective use of the electromagnetic spectrum dispute the enemy's use of electronic warfare. USIS 95
electronic distance-measuring (EDM) equipment Devices that measure the phase difference between transmitted and returned (i.e., reflected or retransmitted) electromagnetic waves, of known frequency and speed, or the round trip transit time of a pulsed signal, from which distance is computed. A wide range of such equipment is available for surveying and navigational use. Also called distance measuring equipment (DME). See also electronic position indicator; Electrotape; Geodimeter; laser; sonar; Tellurometer. HDBK-850
electronic intelligence (ELINT) (DOD) Technical and geolocation intelligence derived from foreign non-communications electromagnetic radiations emanating from other than nuclear detonations or radioactive sources. See also electronic warfare (EW); intelligence; signals intelligence (SIGINT); telemetry intelligence (TELINT). JPUB 1-02
electronic line of position A line of position established by means of electronic equipment. HDBK-850
electronic mail (e-mail) The electronic generation, transmission, and display of correspondence and documents. Electronic mail is a Generic Application Environment (GAE). TAFIM 3.0
electronic map Consists of the information of a map or chart, that is captured, stored, and displayed by electronic means. See also raster; raster data structure; Raster Product Standard(s) (RPS); vector; vector data; Vector Product Format (VPF); Vector Product Standard (VPS). HDBK-850
electronic map data (EMD) See electronic map. HDBK-850
Electronic Order of Battle A listing of noncommunications electronic devices including site designation, nomenclature, location, site function, and any other pertinent information obtained from any source that has military significance when related to the devices. USIS 95
electronic position indicator (EPI) A type of electronic distance measuring equipment used primarily in hydrographic surveying. The offshore range has been extended from the limits of shoran distances to more than 500 miles by use of EPI. HDBK-850
electronic refraction The refraction due to the effects of the atmosphere and the ionosphere, which introduce appreciable changes in the quantities measured by means of electronic devices, such as in the phase differences measured with interferometers, in the rate of change of phase measured with the Doppler systems, and in the change in phase between the times of transmitting and receiving a signal by the ranging instruments. HDBK-850
electronic reporting product A product intended to be originally disseminated electronically. USIS 95
electronic sketchmaster See universal analog photographic rectification system. HDBK-850
electronic survey Any survey utilizing electronic equipment. HDBK-850
Electronic System Center The Air Force Material Command (AFMC) center for command, control, communications and intelligence research and development. Located at Hanscom Air Force Base, MA. USIS 95
electronic telemeter An electronic device that measures the phase difference or transit time between a transmitted electromagnetic impulse of known frequency and speed and its return. HDBK-850
electronic transmission Electronic transmission encompasses the capabilities required to send imagery operations data to other delivery nodes electronically. Electronic transmission focuses on expeditiously retrieving archive and/or unprocessed imagery data available to a delivery node and transmitting it, via electronic means (e.g., local area network, metropolitan area network) to another delivery node. USIS 95
electronic warfare (EW) (DOD) Any military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy. USIS 95
electro-optical imaging A type of sensor providing a digitized gray scale depiction of the Earth's surface. USIS 95
electro-optical intelligence (ELECTRO-OPTINT) (DOD) Intelligence information derived from the optical monitoring of the electromagnetic spectrum from ultraviolet (0.01 micrometer) through far (long wavelength) infrared (1,000 micrometers). JPUB 1-02
electro-optics The technology associated with those components, devices and systems that are designed to interact between the electromagnetic (optical) and the electric (electronic) state. USIS 95
Electrotape A trade name for a precise electronic surveying device which transmits a radio frequency signal to a responder unit which in turn retransmits the signal back to the interrogator unit. The time lapse between original transmission and receipt of return signal is measured and displayed in a direct digital readout for eventual reduction into a precise linear distance. It operates on the same principal as the Tellurometer. HDBK-850
element {JTA} A service area, interface, or standard within the JTA document. JTA 2.0
elements of a fix The specific values of the coordinates used to define a position. HDBK-850
elevated pole The celestial pole above the horizon. Opposite of depressed pole. HDBK-850
elevation Vertical distance from a datum, usually mean sea level, to a point or object on the Earth's surface; not to be confused with altitude which refers to points or objects above the Earth's surface. In geodetic formulas, elevations are heights: h is height above ellipsoid, H is height above the geoid or local datum. Occasionally the h and H may be reversed. See also adjusted elevation; assumed ground elevation: barometric elevation; checked spot elevation; critical elevation; difference of elevation; dynamic elevation; field elevation; fixed elevation; highest elevation; mean ground elevation; optimum ground elevation; orthometric elevation; preliminary elevation; spot elevation; standard elevation; supplemental elevation; unchecked spot elevation. HDBK-850
elevation angle See angle of elevation. HDBK-850
elevation density category A term used throughout sizing of digital elevation data transactions within the MARK 90 system. Elevation density category 1 represents elevation post spacing at 3 arc second intervals. A product having a scale smaller than 1:50,000 would typically be represented by this density. Elevation density category 2 represents elevation post spacing at 1 arc second intervals. A product having a scale of 1:50,000 or larger would typically be represented by this density. HDBK-850
elevation matrix A series of height values for points spaced at regular intervals and usually expressed in the form of a two-dimensional array of numbers. HDBK-850
elevation meter A mechanical or electromechanical device on wheels that measures slope and distance, and automatically and continuously integrates their product into difference of elevation. HDBK-850
elevation posts A point with a known horizontal and vertical position with respect to some defined reference system. Post points are common elevation points between two different digital terrain files. Digital Terrain Elevation Data are elevation posts in digital form. A digital elevation matrix consists of elevation posts evenly distributed in a rectangular pattern. HDBK-850

elevation tints

See hypsometric tinting.

HDBK-850

ellipsoid

An ellipsoid is a mathematical figure generated by the revolution of an ellipse about one its axes. The ellipsoid that approximates the geoid is an ellipse rotated about its minor axis, or an oblate spheroid. See also datum-centered ellipsoid; Earth-centered ellipsoid; Fischer ellipsoid of 1960; triaxial ellipsoid.

HDBK-850

ellipsoid

(UCDM Entity: "ELLIPSOID") An approximation of the shape of the Earth through the rotation of an ellipse about its minor axis.

USIGS/CDM-A

ellipsoid of revolution

See ellipsoid of rotation.

HDBK-850

ellipsoid of rotation

The surface generated by an ellipse rotating about one of its axes. Also called ellipsoid of revolution. See also oblate spheroid; prolate spheroid.

HDBK-850

ellipsoidal height

Distance of a point from the geodetic ellipsoid measured along the perpendicular to the ellipsoid at the point, with height of points outside the ellipsoid being treated as positive. Also called geodetic height.

CEN/TC 287

ellipsoidal reflector

A mirror surface which conforms to a portion of an ellipsoid of revolution, Principally employed in several types of stereoplotter projectors such as the ER-55 .

HDBK-850

elliptical error probable

Used to determine potential accuracy.

USIS 95

ellipticity of an ellipse

The ratio between the difference in length of the semi-axes of an ellipse and its semimajor axis.

HDBK-850

ellipticity of the spheroid

See flattening (of the Earth).

HDBK-850

elongation

1. (surveying) The position of a celestial body relative to the observer's meridian, is such that the apparent azimuthal movement is at a minimum. 2. The angular distance of a body of the solar system from the Sun; the angle at the Earth between lines to the Sun and another celestial body of the solar system. See also greatest elongation.

HDBK-850

emergency run

See tide over run.

HDBK-850

emergent nodal point

See nodal point, definition 1.

HDBK-850

emerging standard

A specification that is under consideration by an accredited standards development organization, but that has not completed the process of approval by the sponsoring body. Emerging standards are often subject to significant change prior to approval.

IEEE P1003.0

emissivity

The amount of energy given off by an object relative to the amount given off by a "blackbody" at the same temperature. Normally expressed as a positive number between zero and one.

HDBK-850

emissivity

The relative effectiveness of an object's surface in emitting thermal energy.

USIS 95

emitted radiance

The total thermal energy emitted (not reflected) from an object. An object emits thermal energy according to its temperature (e.g., hot stove) and emissivity.

USIS 95

emphasis

See target emphasis.

USIS 95

emphasis nominations

A special attention request for imagery or imagery-derived information.

USIS 95

empirical orientation (rectification)

The composited rectified adjustments of magnification, swing, easel tilt, y-displacement, and x-displacement used to correctly recreate the exact conditions in the projected image that existed in the negative at the instant of exposure.

HDBK-850

emulsion

A suspension of either light-sensitive silver salts, Diazos, or photopolymers, in a colloidal medium which is used for coating films, plates, and papers.

HDBK-850

emulsion-to-base

A contact exposure in which the base of the copying film is in contact with the emulsion side of the sheet being copied. See also emulsion-to-emulsion.

HDBK-850

emulsion-to-emulsion

A contact exposure in which the emulsion of the copying film is in contact with the emulsion of the sheet being copied. See also emulsion-to-base.

HDBK-850

encapsulation

A software development technique that consists of isolating a system function or a set of data and operations on those data within a module and providing precise specifications for the module. [IEEE 610.12]

IEEE 610-1990

encode

To convert data by the use of a code or a coded set in such a manner that reconversion to the original form is possible.

HDBK-850

encoding

The conversion of data into a series of codes.

ISO/TC 211

encoding [process]

The process of representing information content and structure into a format suitable for transfer or storage.

ISO/TC 211
encoding formalism Methods needed and applied in defining an encoding schema. CEN/TC 287
encoding rule An identifiable collection of rules that are used in the encoding process to convert instances of information into instances of data in a data structure. NOTE - An encoding rule specifies the syntax, codes and encapsulations used to produce a data structure. ISO/TC 211
encoding schema Schema that defines the structure of the encoded data by naming feasible data segments and their elements, by giving their possible order and by listing possible data values of the data elements. CEN/TC 287
encryption The process of "encoding" data so it cannot be interpreted by anyone or any machine that does not have the "code." Multimedia
end lap See overlap, definition 1. HDBK-850
end node 1. The second node of an edge (an edge is traversed from the start node to the end node). 2. The last node of a feature with several edges. 3. The last node of an areal feature which is coincident with the first node. HDBK-850
Enemy Situation Correlation Element An intelligence division within the AOC responsible for supporting the execution of the Air Tasking Order (ATO). USIS 95
energy storage The safe, compact storage of electrical or chemical energy, including energetic materials for military systems. USIS 95
Engineer Topographic Laboratories (ETL) Now the United States Army Topographic Engineering Center (USATEC). USATEC Web Site
engineer's chain Similar to a Gunter's chain except that it is 100 feet in length and contains 100 links, each 1 foot long. HDBK-850
engineer's level Any of a group of precision leveling instruments for establishing a horizontal line of sight, used to determine differences of elevation. HDBK-850
Engineering Change Proposal (ECP) types A term covering the subdivision of Class I Engineering Change Proposals on the basis of the completeness of the available information delineating and defining the engineering change. They will be identified as preliminary or formal. (MIL-STD-973) DISA CFS
Engineering Development The term associated with DoD Category 6.4 includes those projects in engineering and manufacturing development for Service use. This area is characterized by major line item projects and program control will be exercised by review of individual projects. Engineering Development includes engineering and manufacturing development projects (DoD 5000.1). USIS 95
engineering map A map showing information that is essential for planning an engineering project or development and for estimating its cost. HDBK-850
Engineering Review Board (ERB) A subpanel of a Configuration Control Board (CCB) to review proposed changes to an item, segment or system under configuration management prior to submission to the CCB. The ERB recommends approval/disapproval of proposed changes. USIS 95
engineering survey A survey executed for the purpose of obtaining information that is essential for planning an engineering project or development and estimating its cost. The information obtained may, in part, be recorded in the form of an engineering map. HDBK-850
Engineering Viewpoint A viewpoint on a system and its environment that focuses on the mechanisms and functions required to support distributed interaction between objects in the system. RM-ODP
engraver See scriber. HDBK-850
engraver subdivider A specially designed scribing instrument which permits the selection of uniform tick spacing in subdividing or ticking map projections. HDBK-850
Enhanced Tactical Radar Correlator (ETRAC) A U.S. Army mobile system designed to receive and process synthetic aperture radar phase history data into imagery for exploitation by the Imagery Processing and Dissemination system (IPDS). The projected fielding date of the first system is May 1995 and will go to the 18th Airborne Corps, Ft. Bragg, NC. USIS 95
Enhanced Tactical Users Terminal (ETUT) A U.S. Army ground transportable, system-high security level data processing terminal that provides expanded communications interconnectivity and automated collection management support. USIS 95
Enhanced Visualization for Intelligence and Operational Needs An imagery perspective transformation system for real-time scene generation and 3-D modeling of operational scenes. USIS 95
enlargement A negative, diapositive, or paper print made at a larger scale than the original. Also called blow up. HDBK-850
enlargement factor See scale of reproduction. HDBK-850
enlargement/reduction diagram Chart showing the necessary lens extension and copy board extension required for various enlargements and reductions. HDBK-850
enroute chart A chart of air routes in specific areas that shows the exact location of electronic aids to navigation, such as radio direction finder stations, radio and radar marker beacons, and radio range stations. Also called radio facility chart. HDBK-850
enterprise Any system of components - cultural, process and technology - that interact to accomplish strategic goals and objectives. An enterprise may be a company, an organization, a government office, a project, a dicision of a company, etc. ISEE 97
enterprise Literally, a business organization. In the computer industry, the term is often used to describe any large organization that utilizes computers. An intranet, for example, is a good example of an enterprise computing system. PC Webopaedia
enterprise The highest level in an organization-includes all missions and functions. TAFIM 3.0
enterprise An organization that performs some task or group of tasks in relation to the rest of the world. Webster Computer
enterprise integration (EI) A tactical strategy and an implementing process for using information as a strategic asset to manage DOD far more effectively and efficiently. It bridges functional and technical boundaries in DOD and with industry, allies, and coalition partners to promote communication, increase flexibility, and avoid waste and duplication. [DISA/D7] DISA CFS
Enterprise Integration Corporate Management Council (EICMC) Senior leadership forum for identifying and resolving DOD-wide issues arising from accelerated process reengineering, data standardization and sharing, and migration system implementation. Co-chaired by the ASD(C3I) and the PDUSD(A & T). [DISA/D7] DISA CFS
enterprise model In general an enterprise model consists of a description of things over which the organisation has control (such as people, material or processes) and a description of what the organisation can do with those things (such as hire, purchase or analyse respectively). The model need not be all encompassing: it could be a significant subset of things over which the organisation has control. Fraser94
enterprise model A model of how an organization does business. Information systems are designed from this model. Freedman 1995
enterprise model A high level model of an organizatio''s mission, function, and information architecture. The model consists of a function model and a data model. TAFIM 3.0
Enterprise Viewpoint A viewpoint on a system and its environment that focuses on the purpose, scope, and policies for that system. RM-ODP
entity 1. A representation of a collection of data elements in a conceptual schema. 2. A class of objects with common properties. [ISO 10303:11] ISO/TC 211
entity Any concrete or abstract thing of interest. While in general the word entity can be used to refer to anything, in the context of modeling it is reserved to refer to things in the universe of discourse being modeled. RM-ODP
entity An active element within an open system layer (e.g., session entity, transport entity). It can represent one layer, one part of a layer, or several layers of the OSI Reference Model. One layer can include several entities. TAFIM 3.0
entity A set of real or abstract things (people, objects, ideas, pairs of things, etc.) which have common characteristics or "attributes" and are of interest to the organization. USIGS/CDM-A
entity attribute A description of an element of an entity. ISO/TC 211
entity node One of the two node primitive types. It is used to represent isolated features that are zero dimentional at a particular scale. Entity nodes are topologically linked to a containing face when face topology is present. Entity nodes cannot occur on edges. See also node and connected node. VPF Glossary
entity point Points used to represent features that are zero-dimensional (such as survey points). Entity points may be topologically linked to a containing face. HDBK-850
entity relationship A logical link between entities. ISO/TC 211
entity set An attribute table or group of attributes. HDBK-850
entity type A definition and description of a set into which similar entity instances are classified. ISO/TC 211
entrance pupil The image of the aperture stop formed by all the lens elements on the object side of the aperture stop. HDBK-850
entrance slit Slit through which energy enters a spectroscopic instrument. HDBK-850
entrance window The image of the field stop formed by all the lens elements on the object side of the field stop. HDBK-850
envelope In a Message Handling System, part of a message that contains information necessary to deliver the message to the recipient. In addition, the envelope may contain information that identifies the message originator and potential recipients, records details of the routing by the message transfer system, and characterizes the message content. [DISA/D2] DISA CFS
environment {DII COE} In the context of the COE, all software that is running from the time the computer is rebooted to the time the system is ready to respond to operator queries after operator login. This software includes the operating system, security software, installation software, windowing environment, COE services, etc. The environment is subdivided into a runtime environment and a software development environment. DII COE IRTS
environment The circumstances or conditions in which a software system executes. This includes interfaces with an operating system, interfaces with other systems, dependency on database management systems, hardware or network constraints, or any factor that affects the functioning of the software system. S/W Reuse
Environment Extension {DII COE} The process of a segment issuing requests to the COE tools to expand the environment. The principle of environment extension is important because it allows for segments to be easily added or removed, and it eliminates unarbitrated environmental conflicts between segments. DII COE IRTS
Environment Extension File {DII COE} A file that contains runtime environmental extensions for the COE. Segments use extension files to add their own environment variables to the runtime environment, additions to the X Windows environment, etc. Environment extension files are the technique for encapsulating a segment's contribution to the runtime environment so that its environment effects can be easily added or removed. DII COE IRTS
environment of an object The part of the model which is not part of that object. The set of actions associated with an object is partitioned into internal actions and interactions. An internal action always takes place without the participation of the environment of the object. An interaction takes place with the participation of the environment of the object. RM-ODP
environmental effects The study, modeling, and simulation of atmospheric, oceanic, terrestrial, and space environmental effects, both natural and man made, including the interaction of a weapon system with its operating medium and man produced phenomena such as obscurant found on the battlefield. USIS 95
Environmental Protection Agency (EPA) The EPA is an independent United States Government Agency founded in 1970. The mission of the EPA is to protect human health and to safeguard the natural environment - air, water, and land - upon which life depends. The EPA is headquartered in Washington, DC. EPA Web Site
EnviSat Scheduled for launch by the European Space Agency (ESA) in 1999, EnviSat's primary objectives are: to provide for continuity of the observations started with the ESA Remote Sensing (ERS) satellites, including those obtained from radar-based observations; to provide for enhancement of the ERS mission, notably the ocean and ice mission; to extend the range of parameters observed to meet the need to increase knowledge of the factors determining the environment; to make a significant contribution to environmental studies, notably in the area of atmospheric chemistry and ocean studies (including marine biology). EnviSat-1 will fly in a sun-synchronous polar orbit of about 800 km altitude. The repeat cycle of the reference orbit is 35 days, and for most sensors, being wide swath, it provides a complete coverage of the globe within one to three days. ESA Web Site
Eötvös correction Component of uncorrected observed gravity obtained on a moving platform that is attributed to the east-west component of the velocity that either increases or decreases the effect of the centrifugal force caused by the Earth's rotation. The formula for the correction usually includes the term for the secondary velocity correction. HDBK-850
Eötvös effect A vertical force experienced by a body moving in an east-west direction on the rotating Earth. In gravity measurements, a positive correction is applied if moving eastward, and a negative correction if moving westward. HDBK-850
Eötvös unit The unit of gravitational gradient 10-9 meters per second per second per meter. HDBK-850
ephemeris (JCS) A publication giving the computed places of the celestial bodies for each day of the year, or for other regular intervals. [A publication giving similar information in a form suitable for use by a navigator is called an almanac. An ephemeris is also a statement, not necessarily in a publication, presenting a correlation of time and position of celestial bodies or man-made satellites. A short ephemeris of future location/time of satellite is known as a set of alerts.] See also broadcast ephemeris; precise ephemeris. HDBK-850
ephemeris A tabular statement giving the computed places of space objects for regular intervals (such as a table of calculated coordinates and velocity vector of a space object with equidistant times specified.) USIS 95
ephemeris time The uniform measure of time defined by the laws of dynamics and determined in principal from the orbital motions of the planets, specifically in the orbital motion of the Earth as represented by Newcomb's "Tables of the Sun" Ephemeris time for close-Earth satellites, or more correctly the time associated with satellite ephemerides, is observation dependent. For example, if the observations were made in universal time (UT), the ephemeris time is UT; if the observations were made in international atomic time (TAI), the ephemeris time is in TAI. HDBK-850
epipolar plane (photogrammetry) Any plane which contains the epipoles, therefore, any plane containing the air base. Also called basal plane. HDBK-850
epipolar ray The line on the plane of a photograph joining the epipole and the image of an object. Also expressed as the trace of an epipolar plane on a photograph. HDBK-850
epipoles In the perspective setup of two photographs (two perspective projections), the points on the planes of the photographs where they are cut by the air base (extended line joining the two perspective centers). In the case of a pair of truly vertical photographs, the epipoles are infinitely distant from the principal points. HDBK-850
epoch 1. A particular instant for which certain data are given. 2. A given period of time during which a series of related acts or events takes place. 3. An arbitrary moment in time to which measurements of position for a body or orientation for an orbit are referred. HDBK-850
Equal Arc Second Raster Chart/Map (ARC) A rectangular coordinate and projection system at any scale for the entire ellipsoid based on the World Geodetic System 1984 (WGS84). The ARC system divides the ellipsoid surface into 18 overlapping latitudinal band scaled zones. HDBK-850
equal energy Spectral distribution characterized by equal flux per unit wavelength interval. HDBK-850
equal-altitude observations Observations of celestial objects at a fixed altitude (such as by an astrolabe) taken at more or less uniformly spaced azimuths around the horizon HDBK-850
equal-altitude observations of the Sun Azimuth observations that consist of measuring horizontal angles from a southerly reference point to the Sun's limbs at an identical vertical angle, if measured to the right limb in the a.m., then the angle should be measured to the left limb in the p.m. The same limb should be observed in vertical angle. The mean of the two horizontal angles, with small correction for the change in the Sun's declination during the interval from the a.m. to the p.m. readings, gives a resulting horizontal angle to the meridian. HDBK-850
equal-area map projection A map projection having a constant area scale. Such a projection is not conformal and is not used for navigation. Also called authalic map projection; equivalent map projection. HDBK-850
equation See angle equation; azimuth equation; condition equation; correlate equation; error equation; Eule''s equation; hydrostatic equation; Laplace equation; latitude equation; length equation; longitude equation; lunar equation; normal equation; observation equation; parametric equations; perpendicular equation; personal equation; side equation; side equation tests. HDBK-850
equation of the equinox The difference between the mean and true right ascensions of a body on the Equator, thus the difference between mean and apparent sidereal time. Also called nutation in right ascension. HDBK-850
equation of time The algebraic difference in hour angle between apparent solar time and mean solar time, usually labeled "+" or "-" as it is to be applied to mean solar time to obtain apparent solar time. HDBK-850
Equator The great circle on the Earth midway between the poles and in a plane perpendicular to the Earth's axis of rotation. It is the line of 0 latitude. See also astronomic equator; celestial equator; fictitious equator; galactic equator; geodetic equator; geomagnetic equator; grid equator; lunar celestial equator; magnetic equator; oblique equator; transverse equator. HDBK-850
equator system See celestial equator system of coordinates. HDBK-850
equatorial axis 1. The diameter of the Earth described between two points on the Equator. 2. (astronomy) A telescope mounting axis oriented parallel to the Earth's rotational axis. HDBK-850
equatorial bulge The excess of the Earth's equatorial diameter over the polar diameter. HDBK-850
equatorial chart 1. A chart of equatorial areas. 2. A chart on an equatorial projection. HDBK-850
equatorial cylindrical orthomorphic chart See Mercator chart. HDBK-850
equatorial cylindrical orthomorphic map projection See Mercator map projection. HDBK-850
equatorial diameter The diameter of the Earth at the great circle comprising the terrestrial equator. HDBK-850
equatorial gravity value The mean acceleration of gravity at the Equator, approximately equal to 9.780 3 m/sec2. HDBK-850
equatorial horizontal parallax The angle at a celestial object subtended by the equatorial semidiameter of the Earth used to indicate the distance of the object from the Earth. HDBK-850
equatorial intervals The angles, expressed in units of time, between the various lines which compose the reticle of an astronomic transit and the mean position of those lines. HDBK-850
equatorial map projection A map projection centered on the Equator. HDBK-850
equatorial node Either of the two points where the orbit of the satellite intersects the equatorial plane of its primary. HDBK-850
equatorial radius The radius assigned to the great circle comprising the terrestrial equator. HDBK-850
equatorial satellite A satellite whose orbit plane coincides, or almost coincides, with the Eart''s equatorial plane. HDBK-850
equatorial stars Stars having declinations close to zero and whose diurnal path is a parallel of declination close to the Equator. Equatorial stars, because of their apparently greater speed of travel, are preferred for time and longitude determinations. HDBK-850
equatorial system See celestial equator system of coordinates. HDBK-850
equiangular spiral See rhumb line. HDBK-850
equiangulator An optical instrument, employing a 60 prism, used to determine astronomic latitude and longitude by equal altitudes of heavenly bodies when the time of the prime meridian (Greenwich) is known at the place of observation. HDBK-850
equigeopotential surface See equipotential surface. HDBK-850
equilibrium A state of balance between forces. A body is said to be in equilibrium when the vector sum of all forces acting upon it is zero. HDBK-850
equilibrium spheroid The shape that the Earth would attain if it were entirely covered by a tideless ocean of constant depth. See also geoid. HDBK-850
equilibrium theory A hypothesis which assumes an ideal Earth which has no continental barriers and is uniformly covered with water of considerable depth. It also assumes that the water responds instantly to the tide-producing forces of the Moon and Sun to form a surface in equilibrium and moves around the Earth without viscosity or friction. See also geoid. HDBK-850
equinoctial See celestial equator. HDBK-850
equinoctial colure The hour circle through the equinoxes. HDBK-850
equinoctial day See sidereal day. HDBK-850
equinoctial point See equinox. HDBK-850
equinoctial system of coordinates See celestial equator system of coordinates. HDBK-850
equinoctial year See tropical year. HDBK-850
equinox One of the two points of intersection of the ecliptic and the celestial equator, occupied by the Sun when its declination is 0. Also called equinoctial point. See also autumnal equinox; mean equinox; vernal equinox. HDBK-850
equipotential surface A surface having the same potential of gravity at every point, Also called level surface. See also geoid; geop; geopotential surface. HDBK-850
equiscalar A surface along which a scalar quantity has a constant value. HDBK-850
equivalent focal length (JCS) The distance measured along the optical axis of the lens from the rear nodal point to the plane of best average definition over the entire field used in a camera. See also focal length. HDBK-850
equivalent map projection See equal-area map projection. HDBK-850
equivalent scale The relationship which a small distance on a graphic bears to the corresponding distance on the Earth, expressed as an equivalence, such as 1 inch (on the graphic) equals 1 mile (on the ground). Also called verbal scale. HDBK-850
equivalent vertical photograph A theoretically, truly vertical photograph taken at the same camera station with a camera whose focal length is equal to that of a camera taking a corresponding tilted photograph. HDBK-850
era A named period. NOTE - The duration of an era, and the point in time at which it begins and ends may be unknown or indefinite. ISO/TC 211
erasable optical disc (EOD) A class of compact discs which allow users to rerecord data onto the disk. HDBK-850
erect image An image that appears upright, or in the same relative position as the object. HDBK-850
erecting telescope An observer sees objects right side up when looking through an erecting telescope and upside down when looking through an inverting telescope. The eyepiece in the optical system of an erecting telescope usually has four lenses, and the eyepiece in the optical system of an inverting telescope has two lenses. See also inverting telescope. HDBK-850
erratic error An error caused by an incomplete element in an instrument, such as backlash in a gear train. See also instrument error. HDBK-850
error 1. The difference between an observed or computed value of a quantity and the ideal or true value of that quantity. 2. An error is generally classified as one of three types: (1) a blunder (mistake) which can be identified and corrected; (2) a systematic error, either constant or variable, which must be compensated for; and (3) a random error, one of the class of small inaccuracies due to imperfections in equipment, surrounding conditions, or human limitations. See also absolute error; actual error; accumulative error; blunder; chronometer error; circuit closure; circular error; circular error probable; circular near-certainty error; circular standard error; clamping error; collimation error; compass index error; compensating error; constant error; curved-path error; eccentric error; erratic error; external error; graduation error; gross error; index error; inherited error; instrument error; law of propagation of error; linear error; mean square error; modulation error; natural error; near-certainty error; orthometric error; parallactic error; periodic errors; personal error; pointing error; positional error; principal-distance error; principal-point error; prismatic error; probable error; random error; residual error; resultant error; scale error; shade error; standard error; systematic error; theoretical error. HDBK-850
error Part of an object state which is liable to lead to failures; a manifestation of a fault in an object. Corrective action may prevent an error from causing a failure. RM-ODP
error budget A correlated set of the individual major error sources with the quantified error or uncertainty which each contributes to a totaI system accuracy or probable error. HDBK-850
error detection and correction A system of codes inserted in telegraph or data signals that conform to specific rules of construction, so that departures in the received signal can be detected and corrected automatically at the receiving terminal before delivery. [Joint Pub 6-02.1] DISA CFS
error equation The probability equation which expresses the laws of the occurrence of random errors. This equation expresses the relationship between observed values, plus first-order correction terms, and theoretical values. The error equation is the basis of the method of least squares, used in the adjustment of observations for determining the most probable value of a result from those observations. HDBK-850
error interval See confidence interval. HDBK-850
error of closure 1. (general) The amount by which a quantity obtained by a series of related measurements differs from the true or fixed value of the same quantity. Also called closing error; closure. 2. (angles) The amount by which the actual sum of a series of angles fails to equal the theoretically exact value of that sum. Also called angular error of closure. 3. (azimuth) The amount by which two values of the azimuth of a line, derived by different surveys or along different routes, fail to be exactly equal to each other. Also called azimuth error of closure. 4. (leveling) The amount by which two values of the elevation of the same bench mark, derived by different surveys or through different survey routes or by independent observations, fail to be exactly equal to each other. Also called leveling error of closure. See also circuit closure. 5. (loop) The error in the closure of a survey on itself. Loops do not protect against systematic errors in distance measurement or blunders in starting position or azimuth. Also called loop error of closure. 6. (horizon) The amount by which the sum of a series of adjacent measured horizontal angles around a point fails to equal exactly 360. Measurement of the last angle of the series is called closing the horizon; also called closure of horizon; horizon closure. 7. (triangle) The amount by which the sum of the three observed angles of a triangle fails to equal exactly 180 plus the spherical excess of the triangle. Also called closure of triangle; triangle closure; triangle error of closure. 8. (traverse) The amount by which a value of the position of a traverse station, as obtained by computation through a traverse, fails to agree with another value of the same station as determined by a different set of observations or routes of survey. Also called closure of traverse; error of survey; horizontal closure error; traverse error of closure. See also linear error of closure; relative error of closure. HDBK-850
error of collimation See collimation error. HDBK-850
error of observation The difference between an observed value of a quantity and a value adopted as representing the ideal or true value of that quantity. HDBK-850
error of run (micrometer) The difference, in seconds of arc, between the intended value of one turn of the micrometer screw and its actual value as determined by measuring the space between two adjacent graduation marks of the circle with the micrometer. Also called run; run of micrometer. HDBK-850
error of survey See error of closure, definition 8. HDBK-850
error of the mean See standard error of the mean. HDBK-850
escape and evasion graphic A map, chart or other graphic, usually produced on a lightweight durable material, specifically designed to guide personnel to safety from enemy held territory. HDBK-850
essential elements of friendly information Key questions likely to be asked by adversary officials and intelligence systems about specific friendly intentions, capabilities, and activities, so they can obtain answers critical to their operational effectiveness. USIS 95
Essential Elements of Information (EEIs) Exploitation requirements or imagery analyst instructions. Standing EEIs are generic observable's for each order of battle and other reportable activities. Ad hoc EEIs reflect the exact intelligence need and state specific questions to be answered. USIS 2-1.1
Essential Products {C4ISR AF} These products constitute the minimal set of products required to develop architectures that can be commonly understood and integrated within and across DoD organizational boundaries and between DoD and multi-national elements. These products must be developed for all architectures. C4ISR AF
establishment See lunitidal interval. HDBK-850
establishment of the port The average interval between upper and lower lunar transit near time of new and full Moon and the next high water. Also called common establishment; high water full and change: vulgar establishment. See also lunitidal interval. HDBK-850
estimate 1. An analysis of a foreign situation, development, or trend that identifies its major elements, interprets the significance, and appraises the future possibilities and the prospective results of the various actions that might be taken. 2. An appraisal of the capabilities, vulnerabilities, and potential courses of action of a foreign nation or combination of nations in consequence of a specific national plan, policy, decision, or contemplated course of action. 3. An analysis of an actual or contemplated clandestine operation in relation to the situation in which it is or would be conducted in order to identify and appraise such factors as available and needed assets and potential obstacles, accomplishments, and consequences. USIS 95
etch 1. To remove selected areas of the emulsion either chemically or manually. 2. Chemical treatment of a lithographic plate to make nonprinting areas grease-repellent and water-receptive or to produce the image on deep etch plates. 3. An acid solution mixed with the dampening fountain water on an offset press to help control ink on the pressplate. HDBK-850
etch slip A pencil-shaped abrasive used in removing unwanted marks on a metal pressplate. Also called snakeslip. HDBK-850
etched zinc plate An etched copy of the contour drawing of the base map, used as the guide in cutting the stepped terrain base of a model for making relief models. HDBK-850
Ethernet A local-area network (LAN) protocol developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus topology and supports data transfer rates of 10 Mbps. The Ethernet specification served as the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. Ethernet uses the CSMA/CD access method to handle simultaneous demands. It is one of the most widely implemented LAN standards. A new version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. And a proposed standard, called Gigabit Ethernet will support data rates of 1 gigabit (1,000 megabits) per second. PC Webopaedia
Ethernet A type of network system that allows audio and video information to be carried as well as computer data. Webster Computer
Eulerian angles A system of three angles which uniquely defines with reference to one coordinate system (e.g. Earth axis) the orientation of a second coordinate system (e.g. the axis of an orbit). HDBK-850
Euler's equation A relation in a parabolic orbit involving two radius vectors, their chord, and the time interval between them. HDBK-850
Euler's theorem A mathematical expression to obtain the radius of curvature of a normal section in any azimuth on the reference ellipsoid. The azimuth angle, and the radius of curvature in the meridian and in the prime vertical must be known. HDBK-850
European datum The initial point of this system is located at Potsdam, Germany. Numerous national systems have been joined into a large datum based upon the international ellipsoid which was oriented by the astrogeodetic method. The European and African triangulation chains have been connected and the gap of the African arc measurement from Cairo to Cape Town has been filled. Thus, all of Europe, South Africa, and North Africa are molded into one system. Through common survey stations, it was also possible to convert data from the Russian Pulkovo 1932 system to the European datum and, as a result, the European datum includes triangulation as far east as the 84th meridian. Additional ties across the Middle East have permitted connection of the Indian and European datums. See also preferred datum. HDBK-850
European Intelligence Support System Capabilities include indications and warning, automated message handling, and General Military Intelligence (GMI). USIS 95
European Space Agency (ESA) Established in 1980, the ESA is a multi-national organization whos mission is to provide for and to promote, for exclusively peaceful purposes, cooperation among European States in space research and technology and their space applications, with a view to their being used for scientific purposes and operational space applications systems. The ESA has its headquarters in Paris, France. ESA Web Site
European Space Agengy (ESA) Remote Sensing Satellite (ERS) ERS-1 and ERS-2 are the most sophisticated Earth observation satellites ever developed in Europe. ERS-1 was launched in July 1991 on an Ariane 4 launcher. Its payload consists essentially of two specialized radars plus an infrared sensor. In April 1995, ESA launched ERS-2, a carbon copy of its predecessor with one important difference: ERS-2's payload includes a new instrument named GOME, for Global Ozone Monitoring Equipment, purpose designed to measure stratospheric and tropospheric ozone, an important step in the race to fully assess yet another environmental challenge. The Active Microwave Instrument - the biggest system on-board ERS - produces extremely detailed images of a 100 km swath of the Earth's surface : 4.5 million pixels per second, downlinked directly to Earth. In wind and wave modes, the instrument measures continuously and globally wind speed and direction and ocean wave parameters. The Radar Altimeter, the second instrument on ERS, measures with fantastic precision variations in the satellit''s height above sea-level and ice. And the third Instrument, the Along-Track Scanning Radiometer, constructs detailed pictures of the thermal structure of the seas and oceans from surface temperature measurements correct to better than 0.5 degrees Celsius. ESA Web Site
European Space Operations Centre (ESOC) ESOC is the European Space Agency's (ESA) establishment responsible for controlling ESA satellites. ESOC is located in Darmstadt, Germany.' ESA Web Site
European Space Research and Technology Centre (ESTEC) ESTC is the biggest of the European Space Agency's (ESA) establishments. ESTEC is responsible for the technical preparation and management of ESA space projects. ESTEC is located in Noordwijk in the Netherlands. ESA Web Site
European Space Research Institute (ESRIN) ESRIN is the European Space Agency's (ESA) Centre in charge of the exploitation of the Agency's Earth Observation satellites and of all of ESA's non-operational data processing and information systems. ESRIN's primary objective is the exploitation of remote sensing data from ESA and non-ESA Earth Observation missions. ESRIN is located in Frascati, Italy. ESA Web Site
evaluation In intelligence usage, appraisal of an item of information in terms of credibility, reliability, pertinency, and accuracy. Appraisal is accomplished at several stages within the intelligence cycle with progressively different contexts. 1. Appraisal of the worth of an intelligence activity, information, or product in terms of its contribution to a specific goal; or the credibility, reliability, pertinency, accuracy, or usefulness of information in terms of an intelligence need 2. Evaluation may be used without reference to cost or risk, particularly when contrasted with assessment; it is also a process in the production step of the intelligence cycle. USIS 95
evaluation of data set quality The determination of the conformance of a data set to a quality level prescribed by the product specification based on estimated data quality metric value. ISO/TC 211
evection A perturbation of the Moon in its orbit due to the attraction of the Sun. This results in an increase in the eccentricity of the Moon's orbit when the Sun passes the Moon's line of apsides and a decrease when perpendicular to it. See also lunar inequality, definition 1. HDBK-850
event Something (e.g., a change in the state of a geographic feature) which occurs at an instant in time. ISO/TC 211
event (UCDM Entity: "EVENT") A significant occurance. USIGS/CDM-A
Everest spheroid (ellipsoid) A reference ellipsoid having the following approximate dimensions: semimajor axis - 6,377,276.3 meters; flattening or ellipticity - 1/300.80. Used in India, Burma, Pakistan, Laos, Cambodia, Thailand, and Vietnam. HDBK-850
evolution (system) Spreading in scope while increasing functionality and flexibility. C4ISR AF
exaggerated stereo See hyper-stereoscopy. HDBK-850
exchange structure Computer-interpretable format used for storing, accessing, transferring and archiving data. CEN/TC 287
Executable Test Suite (ETS) The set of executable test cases necessary to perform conformance testing of an implementation against a standard or group of standards. ISO/TC 211
Executive Council on Modeling and Simulation (EXCIMS) The mission of the DoD EXCIMS is to advise and assist the Under Secretary of Defense for Acquisition and Technology (USD(A&T)) in strengthening the uses of modeling and simulation (M&S) in the Department of Defense (DoD). DMSO Web Site
Executive Information System (EIS) An information system which supports executive decision-making, provides meaningful presentations of data, and depends upon underlying sources of data. [DISA/DO3 (CIO)] DISA CFS
existent corner A corner whose position can be identified by verifying the evidence of the monument or its accessories, by reference to the description that is contained in the field notes; or where the point can be located by an acceptable supplemental survey record, some physical evidence, or testimony. HDBK-850
existing data Source material and/or information assumed or known to be in the possession of a given source and subject to "off-shelf" collection, as in contrast to data obtained by operational field surveys. HDBK-850
exit pupil The image of the aperture stop formed by all the lens elements on the image side of the aperture stop. HDBK-850
exit window The image of the field stop formed by all the lens elements on the image side of the field stop. HDBK-850
exmeridian altitude An altitude of a celestial body near the celestial meridian of the observer to which a correction is to be applied to determine the meridian altitude. HDBK-850
exmeridian observation Measurement of the altitude of a celestial body near the celestial meridian of the observer, for conversion to a meridian altitude; or the altitude so measured. HDBK-850
Expeditionary Tactical Airborne Reconnaissance System A Tactical Intelligence and Related Activities (TIARA) program associated with the Marine Corps and their AV-8B Harriers. USIS 95
experience radar prediction The determination of size, shape, and relative intensity of radar returns and a determination of radar shadow and no-return areas based primarily on the radar knowledge and experience of the individual making the prediction rather than on proven formulas, power tables, or graphs. Also called artwork prediction. HDBK-850
experimental map A sample of a new map product prepared either to obtain user approval of the adequacy of content and symbolization or to disclose any problems which may occur in the various production stages. Also called prototype. See also pilot sheet. HDBK-850
expert system An AI [automated information] application that uses a knowledge base of human expertise for problem solving. Its success is based on the quality of the data and rules obtained from the human expert. In practice, expert systems perform both below and above that of a human. An expert system contains a knowledge base of if-then-else rules that are processed through an inference engine (software) that uses a variety of techniques to obtain the result. Freedman 1995
explement The difference between an angle and 360. HDBK-850
exploitation The process of obtaining usable data from imagery. HDBK-850
exploitation The evaluation of an image or multiple images to extract the information contained within the image(s) as it pertains to a specific list of questions or general categories of questions. Exploitation may result in the creation of a report or product to disseminate the information, whether it be to a requester or to a database. USIS 95
Exploitation and Reporting (XREP) Coordinating Committee The imagery community's point of coordination for exploitation and reporting activities. USIS 2-1.1
Exploitation and Reporting Structure (EARS) The Exploitation and Reporting Structure is the framework of policy, principles, operating procedures, and standardization that governs the conduct of geospatial exploitation and reporting activities. USIS 95
Exploitation Center Analysis Tool (ECAT) CIO's [NIMA's] discrete event simulation tool that provides the capability to model the business processes within an exploitation center. The building blocks are based on the Exploitation Process Reengineering Study (ExPReS) IDEF model. ECAT can be used in conjunction with the Architecture Simulation Analysis Platform (ASAP). USIS 95
exploitation element Exploitation elements provide the capability to analyze imagery, extract and record information derived from imagery and attach information to imagery, for use by other system elements. USIS 95
exploitation operations support Those required capabilities needed to support the planning for and subsequent acquisition, retrieval, and manipulation of imagery and collateral data (defined here as any data required in support of exploitation other than the primary images identified for exploitation). USIS 95
Exploitation Problem Set (EPS) An independent group of targets, directly linked or affiliated with an Intelligence Problem, that specifies the phase of exploitation. The EPS is one of the elements that comprise the formal structure for organizing and managing national imagery collection, exploitation, and reporting requirements. USIS 95
exploitation product Result of exploitation in the form of an IMINT product or imagery interpretation report. USIS 95
exploitation reporting All activities involved in producing and communicating imagery intelligence reports. USIS 95
Exploitation Requirement Replaces Exploitation Problem Set (EPS) terminology. Identifies the information to be extracted from an image or from imagery including target(s), exploitation phase, and explicit or implied exploitation product requirement. USIS 95
Exploitation Research and Development Subcommittee (EXRAND) EXRAND was the Community subcommittee chartered by the former Committee for Imagery Requirements and Exploitation (COMIREX). EXRAND functions will continue under the guidance of CIO [NIMA] and the Imagery Research and Development Council (IMRAD) . It is the central working group to support and conduct IMRAD-directed actions. USIS 95
Exploitation Supervisor Terminal Associated with several softcopy exploitation systems. USIS 95
exploitation support and management Exploitation support and management functions provide for the control and direction of all (to include national, departmental, and tactical) imagery exploitation and operational support to that task. Encompasses the planning, task assignment, task monitoring, and workload allocation of imagery and personnel resources against imagery exploitation requirements. USIS 95
Exploitation Support Segment A Joint Service Imagery Processing System (JSIPS) segment. USIS 95
exploitation systems Automated or semiautomated computer systems that support image processing, imagery analysis, reporting, imagery dissemination, and intelligence data base maintenance. USIS 95
Exploratory Development The DoD term associated with DoD [R&D] Category 6.2. This activity translates promising basic research into solutions for broadly defined military needs, short of major development projects. This type of effort may vary from fairly fundamental applied research to sophisticated bread-board hardware, study, programming and planning efforts that establish the initial feasibility and practicality of proposed solutions to technological challenges. It would thus include studies, investigations, and development effort. The dominant characteristic of this category of effort is that it be pointed toward specific military needs with a view toward developing and evaluating the feasibility and practicability of proposed solutions and determining their parameters. Exploratory Development precedes the system-specific research described in DoD 5000.1. Program control of the Exploratory Development element will normally be exercised by general level of effort. USIS 95
exploratory survey A survey executed for the purpose of obtaining general information concerning areas about which such information is not a matter of record. HDBK-850
exposure 1. The total quantity of light received per unit area on a sensitized plate or film; may be expressed as the product of the light intensity and the exposure time. 2. The act of exposing a light-sensitive material to a light source. 3. One individual picture of a strip of photographs, usually called frame. HDBK-850
exposure interval The time required between successive exposures of a series of photographs for the purpose of obtaining desired forward lap. HDBK-850
exposure station See air station. HDBK-850
exposure time The time during which a light-sensitive material is subjected to the action of light. HDBK-850
extended color See bleed. HDBK-850
Extended Tether Program A program to evaluate using a longer "line of sight" for an imaging platform. USIS 95
extensibility The ability for a system or components of a system to expand by assimilating new data, software or hardware components. OpenGIS Guide
extension 1. (surveying) See prolongation. 2. (photogrammetry) Extending existing control from a controlled area into an area without control. The term is usually further qualified as horizontal or vertical according to the primary purpose. Also called horizontal extension; horizontal/vertical extension; vertical extension. See also cantilever extension. HDBK-850
extension An addition to the core specifications of a standard. ITSG Vol. 1
extension of control Execution of additional control from existing control by any method. HDBK-850
extent Space covered by a dataset. Space is meant here as Euclidian space but also as a period of time. CEN/TC 287
extent date Date of validity of extent status and extent description. CEN/TC 287
extent status Degree to which a dataset meets its proposed final extent. CEN/TC 287
exterior orientation The determining (analytically or in a photogrammetric instrument) of the position of the camera station and the attitude of the taking camera at the instant of exposure. In stereoscopic instrument practice, exterior orientation is divided into two parts, relative and absolute orientation. Also called outer orientation. See also resection, definition 3. HDBK-850
exterior perspective center See perspective center. HDBK-850
exterior to a curve Any area adjacent to a curve lying toward its convex side, the area not included within the circle of which the curve is part of the circumference. HDBK-850
external distance The distance from the vertex of a circular curve to the middle point of the curve. HDBK-850
external environment A set of entities external to the application platform with which services are provided. External entities include people, exchangeable media that is not mounted in the platform, communication wiring, and other platforms. IEEE P1003.0
External Environment Interface (EEI) The interface between the application platform and the external environment across which services are provided. The EEI is defined primarily in support of system and application interoperability. The primary services present at the EEI comprise Human/Computer Interaction Services Information Services Communication Services IEEE P1003.0
External Environment Interface (EEI) The interface that supports information transfer between the application platform and the external environment. (NIST Special Publication 500-230; TAFIM, Version 3.0, Volumes 1 and 3)) JTA 2.0
external error The repeatability of a measurement with any condition extraneous to the measuring method itself changed; contrasted to internal error. See also standard error. HDBK-850
External Gateway Protocol (EGP) A routing protocol used between gateways on the Internet. OSI Dictionary
externalized object reference An object reference expressed as an ORB-specific string. Suitable for storage in files or other external media. CORBA 2.2
extra foresight (leveling) The rod reading made at an instrument station in a line of levels and on a leveling rod standing on a bench mark or another point not in the continuous line of levels. In spirit leveling there may be one or more extra foresight from a single instrument station or setup, but there can be only one backsight and one foresight from any one instrument station. HDBK-850
extracted target report A target report that contains an account or analysis of imagery-derived information extracted from a data base. USIS 95
extraction Two Dimensional collection of information from a processed image. OGC RFI
extrapolation The process of estimating the value of a quantity beyond the limits of known values by assuming that the rate or system of change between the last few known values continues. HDBK-850
extremely high frequency The frequency band extending from 30 to 300 GHz. USIS 95
eye base See interocular distance. HDBK-850
eyepiece In an optical device, the lens group which is nearest the eye and with which the image formed by the preceding elements is viewed. HDBK-850
eyepiece micrometer See ocular micrometer. HDBK-850

Last Updated by Mark Owens 17 February 1999.