| -- H -- | ||
|---|---|---|
| Term | Definition/Description | Source |
| H and D curve | See characteristic curve. | HDBK-850 |
| H.221 | The ITU-T standard relating to communications protocol for video conferencing. | Multimedia |
| H.261 | The ITU-T Px64 standard relating to the video compression algorithm. | Multimedia |
| hachuring | (JCS) A method of representing relief upon a map or chart by shading in short disconnected lines drawn in the direction of the slopes. | HDBK-850 |
| hack chronometer | A chronometer used for visual reference, and not usually for record purposes. | HDBK-850 |
| halation | (photography) A spreading of a photographic image beyond its proper boundaries, due especially to reflection from the side of the film or plate support opposite to that on which the emulsion is coated. Particularly noticeable in photographs of bright objects against a darker background. | HDBK-850 |
| half mark | See index mark. | HDBK-850 |
| half model | The stereoscopic model formed by the overlap of two adjacent right- or left-hand exposures of convergent photographs. | HDBK-850 |
| half section | Any two quarter sections within a section which have a common boundary; usually identified as the north half, south half, east half, or west half of a particular section. | HDBK-850 |
| half tide level | See mean tide level. | HDBK-850 |
| halftone | (JCS) Any photomechanical printing surface or the impression therefrom in which detail and tone values are represented by a series of evenly spaced dots of varying size and shape, varying in direct proportion to the intensity of the tones they represent. See also halftone screen; middletone. | HDBK-850 |
| halftone screen | (JCS) A series of regularly spaced opaque lines on glass, crossing at right angles, producing transparent apertures between intersections. Used in a process camera to break up a solid or continuous tone image into a pattern of small dots. Also called crossline glass screen. See also contact screen; halftone. | HDBK-850 |
| Hammer projection | A variation, by E. Hammer in 1892, on the zenithal equal-area (Lambert) projection, made by doubling the horizontal distances along each parallel from the central meridian. This transforms the circular shape of the Lambert into an ellipse, similar in appearance to a Mollweide projection, but with all parallels curved except the Equator, which is a straight line. | HDBK-850 |
| hand level | A hand-held instrument for approximate leveling. It consists of a sighting tube with a split field of view; a horizontal cross hair in one-half of the field bisects the image of a spirit level in the other half when the instrument is held level. See also Abney level. | HDBK-850 |
| hand proof | In offset lithography, a proof of a plate made on a hand proof press where operations are manual for inking, dampening, and taking the impression. | HDBK-850 |
| hand templet | A templet made by tracing the radials from the photograph onto a transparent plastic medium. Hand templets are laid out and adjusted by hand to form the radial triangulation. | HDBK-850 |
| handle | An index entry or unique name in software that identifies a catalog entry or other resource so that it can be found and utilized by another software facility. | OpenGIS Guide |
| hand-templet plot | See hand-templet triangulation. | HDBK-850 |
| hand-templet triangulation | A graphical radial triangulation using any form of hand templet. Also called hand-templet plot. | HDBK-850 |
| hanging level | A spirit level so mounted that, when in use, its level tube is lower in elevation than its points of support. | HDBK-850 |
| Harbor and Approach Chart (HAC) | A chart which provides detailed portrayal of navigationally useful information supportive of maneuvering in close quarter areas to berth/anchor, channel keeping while entering/exiting port, or navigating in close proximity to dangers associated with close shore/harbor approach areas. Produced from 1:10,000 to 1:100,000 scale. | HDBK-850 |
| harbor chart | A nautical chart intended for navigation and anchorage in harbors and smaller waterways. | HDBK-850 |
| hardcopy | Products which are printed on paper, photographic materials or other media, and can be interpreted directly by the human user. | HDBK-850 |
| Hardcopy Exploitation Segment (HE/S) | Segment of DMA's [NIMA's] Digital Production System which provides software upgrades for existing [NIMA] photogrammetric equipment and will deliver a new computer for triangulation. Outputs include digital elevation data and rectified and orthorectified imagery. See also Digital Production System; MARK 85. | HDBK-850 |
| hardcopy map | A map printed on paper, photographic materials or other media and can be interpreted directly by the human user. | ISO/TC 211 |
| hardware | Physical equipment used in data processing as opposed to programs, procedures, rules, and associated documentation. | IEEE P1003.0 |
| Hardware Architecture | Assemblage of a computer's internal components and its attached peripheral devices which determine its capabilities and its limitations. [HCI Style Guide] | DISA CFS |
| harmonic | Of a sinusoidal wave, an integral multiple of the frequency of the wave. Note: The frequency of the sine wave is called the fundamental frequency or the first harmonic, the second harmonic is twice the fundamental frequency, the third harmonic is thrice the fundamental frequency, etc. 2. Of a periodic signal or other periodic phenomenon, such as an electromagnetic wave or a sound wave, a component frequency of the signal that is an integral multiple of the fundamental frequency. Note: The fundamental frequency is the reciprocal of the period of the periodic phenomenon. | FED STD 1037C |
| harmonic | A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related. See also compound harmonic motion; gravitational harmonics; sectorial harmonics; simple harmonic motion; spherical harmonics; tesseral harmonics; zonal harmonics. | HDBK-850 |
| harmonic coefficients | The coefficients of trigonometric terms of an infinite series used to approximate an irregular closed surface. See also spherical harmonics. | HDBK-850 |
| harmonic component | Any of the simple sinusoidal components into which a periodic quantity may be resolved. | HDBK-850 |
| harmonic constants | The amplitude and epochs of the harmonic constituents of the tide or tidal current at any place. | HDBK-850 |
| harmonic constituent | See constituent. | HDBK-850 |
| harmonic expressions | Trigonometric terms of an infinite series used to approximate irregular curves in two or three dimensions. | HDBK-850 |
| harmonic function | Any real function that satisfies Laplace's equation. | HDBK-850 |
| harmonic motion | The projection of circular motion on a diameter of the circle of such motion. | HDBK-850 |
| harmonization | The process of ensuring that [standards] profiles do not overlap or conflict. | IEEE P1003.0 |
| Hassler base-line measuring apparatus | An optical base-line measuring apparatus consisting of four rectangular iron bars mounted end to end in a wooden box. Each bar is 2 meters long. The combined length of the apparatus being 8 meters. | HDBK-850 |
| Hayford deflection templets | Templets used in connection with studies for the figure of the Earth and isostasy. In obtaining elevation readings from maps in connection with topographic and isostatic reductions, templets of plastic are used. The templets used in connection with deflection of the vertical studies have circles and radial lines drawn upon them, so proportioned with reference to scale of map and azimuth that land elevations and ocean depths within each compartment formed by adjacent arcs and radii can be easily averaged and the effect of the mass therein on a plumb line at the station (center of circles), under various hypotheses, can be computed. See also Hayford gravity templets. | HDBK-850 |
| Hayford effect | The direct effect on gravity of masses of unit density extending to various distances above and below sea level; it neglects the differences of elevation between the reference spheroid and the geoid. | HDBK-850 |
| Hayford gravity anomalies/Hayford anomalies | Isostatic anomalies obtained by computing the isostatic compensation according to the Pratt theory of isostasy as developed by Hayford, using various depths for purposes of comparative analysis. | HDBK-850 |
| Hayford gravity templets | Templets used in connection with gravity studies which are similar to Hayford deflection templets except that no account is taken of azimuth, all compartments bounded by a given pair of circles being of the same size and shape. A given templet can be used only on maps of the scale and projection for which it is constructed. See also Hayford deflection templets. | HDBK-850 |
| Hayford spheroid (ellipsoid) | A reference ellipsoid having the following approximate dimensions: semimajor axis 6,378,388.0 meters; semiminor axis-6,356,909.0 meters; and the flattening or ellipticity 1/297.00. | HDBK-850 |
| Hayford-Bowie method of isostatic reduction | A method of computing the effect of topography and isostatic compensation on gravity by which the effect of topography is computed directly and then corrected for the effect of isostatic compensation. The mechanics of this method involve the use of the Hayford gravity templets. | HDBK-850 |
| Hayford-Bullard (or Bullard) method of isostatic reduction | A method by which the topographic effect of an infinite slab of density 2.67 and a thickness equal to the elevation of the gravity station is first computed, and then corrected for curvature of the sea level surface and for difference of elevation between the station and the topography. | HDBK-850 |
| haze | The radiance of the atmosphere. | HDBK-850 |
| heading | (JCS) (navigation) The direction in which the longitudinal axis of an aircraft or ship is pointed, usually expressed in degrees clockwise from north (true, magnetic, compass, or grid). | HDBK-850 |
| height | The distance of a point from a chosen reference surface along a line perpendicular to that surface, with heights of points outside the surface treated as positive. | CEN/TC 287 |
| height | (JCS) The vertical distance of an object, point, or level above the ground or other established reference plane. Height may be indicated as follows: very low-below 500 feet but above ground level; low - 500 to 2,000 feet; medium - 2,000 to 25,000 feet; high - 25,000 to 50,000 feet; very high - above 50,000 feet. See also altitude; elevation; ellipsoidal height; geoidal height. | HDBK-850 |
| height anomaly | The difference between the height of a terrain point above the reference spheroid and the corresponding normal height, measured along the normal plumb line. | HDBK-850 |
| height differential | The difference in height between predominant height groupings in a homogeneous surface area. | HDBK-850 |
| height displacement | See relief displacement. | HDBK-850 |
| height finder | A stereoscopic range finder so constructed as to indicate vertical heights rather than slant range. See also stereometer. | HDBK-850 |
| height of instrument | 1. (spirit leveling) The height of the line of sight of a leveling instrument above the adopted datum. 2. (stadia surveying) The height of the center of the telescope (horizontal axis) of transit or telescopic alidade above the ground or station mark. 3. (trigonometric leveling) The height of the center of the theodolite (horizontal axis) above the ground or station mark. | HDBK-850 |
| height of the tide | The vertical distance from chart datum to the surface water level at any stage of the tide usually measured in feet. | HDBK-850 |
| height-of-eye correction | That correction to sextant altitude due to dip of the horizon. Also called dip correction. | HDBK-850 |
| heliocentric | Relative to the center of the Sun as origin. | HDBK-850 |
| heliocentric parallax | See annual parallax. | HDBK-850 |
| HELIOS | A French imaging reconnaissance satellite with an orbital altitude of 250 miles, designed to resolve objects in the 3-6 foot range. The HELIOS mission is military reconnaissance of Europe. | USIS 95 |
| heliotrope | A device used in geodetic surveying for reflecting the Sun's rays to a distant point, to aid in long-distance observations. See also selenotrope. | HDBK-850 |
| helipad | (JCS) A prepared area designated and used for take off and landing of helicopters. (Includes touchdown or hoverpoint.) | HDBK-850 |
| heliport | (JCS) A facility designated for operating, basing, servicing, and maintaining helicopters. | HDBK-850 |
| Helmert's gravity formula of 1901 | A formula for theoretical gravity developed from the gravity observations available at the time (1901), but not fitted to any preassigned value of the Earth's ellipticity. | HDBK-850 |
| Helmert's gravity formula of 1915 | A formula for theoretical gravity based on a triaxial ellipsoid and therefore includes a longitude term. See also longitude term gravity formula. | HDBK-850 |
| hemispherical map | A map of one-half of the Earth's surface, bounded by the Equator, or by meridians. | HDBK-850 |
| hertz (Hz) | The frequency of electrical vibrations (cycles) per second. One hertz is equal to one cycle per second. | USIS 95 |
| hidden lines | Line segments obscured from view in a projected image of a three-dimensional object. | HDBK-850 |
| hierarchy | (digital) A system of classifying features according to feature type and significance. For example, in some cases features with lower numbers are masked out by higher numbered features occupying the same position. | HDBK-850 |
| high altitude | (JCS) Conventionally, an altitude above 10,000 meters (33,000 feet). See also altitude. | HDBK-850 |
| high frequency | The frequency spectrum from 3 MHz to 30 MHz. | USIS 95 |
| High Level Architecture (HLA) | Major functional elements, interfaces, and design rules, pertaining as feasible to all DoD simulation applications, and providing a common framework within which specific system architectures can be defined. (HLA Glossary: www.dmso.mil/projects/hla/docslib/hlagloss.html) | JTA 2.0 |
| high resolution | National Imagery Interpretation Rating Scale (NIIRS) 6.0 to 8.0. | USIS 95 |
| high rod | See long rod. | HDBK-850 |
| high tide | See high water. | HDBK-850 |
| high water (HW) | The highest limit of the surface water level reached by the rising tide. High water is caused by the astronomic tide-producing forces and/or the effects of meteorological conditions. Also called high tide. | HDBK-850 |
| high water full and change (HWF&C) | See establishment of the port. | HDBK-850 |
| high water interval | See lunitidal interval. | HDBK-850 |
| high water line | The line on the bank or shore to which the waters normally rise at high water. In tidal waters, the high water line is, in strictness, the intersection of the plane of the mean high water with the shore. The high water line is the boundary line between the bed and the bank of a stream. | HDBK-850 |
| high water lunitidal interval | See lunitidal interval. | HDBK-850 |
| high water springs | See mean high water springs. | HDBK-850 |
| higher high water (HHW) | The higher of two high waters occurring during a tidal day where the tide exhibits mixed characteristics. | HDBK-850 |
| higher high water interval (HHWI) | The interval of time between the transit (upper or lower) of the Moon over the local or Greenwich meridian and the next higher high water. This expression is use when there is considerable diurnal inequality. See also lunitidal interval. | HDBK-850 |
| higher low water (HLW) | The higher of two low waters of a tidal day where the tide exhibits mixed characteristics. | HDBK-850 |
| higher low water interval (HLWI) | The interval of time between the transit (upper or lower) of the Moon over the local or Greenwich meridian and the next higher low water. This expression is used when there is considerable diurnal inequality. See also lunitidal interval. | HDBK-850 |
| highest elevation | That elevation which is the highest point of relief within the area of a map or chart. See also critical elevation. | HDBK-850 |
| High-Level Language | Programming language that does not reflect the structure of any one computer or class of computers. [HCI Style Guide] | DISA CFS |
| High-Level Operational Concept Graphic | The most general of the architecture-description products and the most flexible in format. Its main utility is as a facilitator of human communication, and it is intended for presentation to high-level decision makers. This kind of diagram can also be used as a means of orienting and focusing detailed discussions. | C4ISR AF |
| Highlight Cable | An electronic reporting product that disseminates one or more free-text target or topic reports that summarize the results of national exploitation deemed by the reporting organization to be of particular intelligence significance. | USIS 95 |
| high-oblique photograph | See oblique air photograph. | HDBK-850 |
| hill plane | The plane containing the positions of three ground marks constituting control points. This may be, but rarely is, a horizontal plane. | HDBK-850 |
| hill shading | (JCS) A method of representing relief on a map by depicting the shadows that would be cast by high ground if light were shining from a certain direction, Also called hillwork. See also shaded relief. | HDBK-850 |
| hillwork | See hill shading. | HDBK-850 |
| historical chart | A chart based on data from previous years to determine probable oceanographic patterns for a specified time. Also called first approximation chart. | HDBK-850 |
| history overlay | A specially prepared matte plastic material which shows the sources of all sounding data used in a bathymetric compilation. | HDBK-850 |
| holiday | (JCS) An unintentional omission in imagery coverage of an area. See also gap. | HDBK-850 |
| hologram | The hologram offers a reconstruction of the external appearance of an object with unique three-dimensional properties. This is accomplished by illuminating the object with coherent light. | HDBK-850 |
| hologrammetry | The art or science of interpreting the three-dimensional holographic image and obtaining reliable measurements by means of holography. | HDBK-850 |
| homogeneous area | An area which has uniform radar reflecting power at all points. | HDBK-850 |
| homogeneous surface area | A grouping of features having the same general surface composition. | HDBK-850 |
| homologous | The condition where an image of a given object point or series of such points is common to two or more projections having different perspective centers. | HDBK-850 |
| homologous images | The images of a single object point that appears on each of two or more overlapping photographs having different perspective centers. | HDBK-850 |
| homologous photographs | Two or more overlapping photographs having different camera stations. | HDBK-850 |
| homologous rays | The two perspective rays corresponding to a pair of homologous image points. | HDBK-850 |
| homolographic (homalographic) map projection | An equal-area map projection. This term is found in the designations given some particular map projections, such as the Mollweide homalographic projection. | HDBK-850 |
| horizon | (JCS) In general, the apparent or visible junction of the earth and sky, as seen from any specific position. Also called the apparent, visible, or local horizon. A horizontal plane passing through a point of vision or perspective center. [The apparent or visible horizon approximates the true horizon only when the point of vision is very close to sea level.] See also apparent horizon; attitude indicator; celestial horizon; false horizon; geocentric horizon; geoidal horizon; geometrical horizon; radar horizon; sensible horizon; true horizon. | HDBK-850 |
| horizon camera | A camera used in conjunction with another aerial camera to photograph the horizon simultaneously with the other photographs. The horizon photographs indicate the tilts of the other photographs. | HDBK-850 |
| horizon closure | See error of closure, definition 6. | HDBK-850 |
| horizon coordinate system | See horizon system of coordinates. | HDBK-850 |
| horizon photograph | 1. A photograph of the horizon taken simultaneously with another photograph for the sole purpose of obtaining an indication of the orientation of the other photograph at the time of exposure. 2. (surveying) A continuous matched set of horizon photographs defining obstructions 360° around a given station. | HDBK-850 |
| horizon prism | A prism which can be inserted in the optical path of an instrument, such as a bubble sextant, to permit observation of the visible horizon. | HDBK-850 |
| horizon profile | A plot of vertical angles against the horizontal angles taken 360° around a point with annotation. See also horizon photograph; horizon sweep. | HDBK-850 |
| horizon sweep | (surveying) A preliminary reconnaissance technique where the instrument is pointed initially at the farthest visible known point and recording clockwise angles to tanks, spires, buildings, signals, etc., for purposes of identification and subsequent use. See also horizon profile. | HDBK-850 |
| horizon system of coordinates | A set of celestial coordinates, usually altitude and azimuth or azimuth angle, based on the celestial horizon as the primary great circle. Also called horizon coordinate system. | HDBK-850 |
| horizon trace | An imaginary line, in the plane of a photograph, which represents the image of the true horizon; it corresponds to the intersection of the plane of a photograph and the horizontal plane containing the internal perspective center or rear nodal point of the lens. See also true horizon. | HDBK-850 |
| horizontal | A level in the sense of being perpendicular to the direction of gravity at a specific local point. NOTE - An important property of a horizontal line is that it belongs to, or is parallel to, a plane tangential to the geoid. | ISO/TC 211 |
| horizontal angle | Angle in a horizontal plane. | HDBK-850 |
| horizontal axis | The axis about which the telescope of a theodolite or transit rotates when moved vertically. | HDBK-850 |
| horizontal bridging | See bridging. | HDBK-850 |
| horizontal circle | A graduated circle affixed to the lower plate of a transit by which horizontal angles can be measured. | HDBK-850 |
| horizontal closure error | See error of closure, definition 8. | HDBK-850 |
| horizontal control | A network of stations of known geographic or grid positions referred to a common horizontal datum, which control the horizontal positions of mapped features with respect to parallels and meridians, or northing and easting grid lines shown on the map. Horizontal control includes basic (marked) and supplementary (unmarked) stations. | HDBK-850 |
| horizontal control datum | A geodetic reference point which is the basis for horizontal control surveys, and of which five quantities are known: latitude, longitude, azimuth of a line from this point, and two constants which arc the parameters of the reference ellipsoid. The horizontal control datum may extend over a continent or be limited to a small area. Also called horizontal datum; horizontal geodetic datum. | HDBK-850 |
| horizontal control point | See horizontal control station. | HDBK-850 |
| horizontal control station | A station whose position has been accurately determined in x- and y-grid coordinates, or latitude and longitude. Also called horizontal control point. | HDBK-850 |
| horizontal control survey net | See survey net, definition 1. | HDBK-850 |
| horizontal coordinate system | (A&D LDM Entity: "HORIZONTAL-COORDINTE-SYSTEM") Reference frame or system from which linear or angular quantities are measured and assigned to the position that a point occupies. | A&D LDM |
| horizontal coplane | See basal coplane. | HDBK-850 |
| horizontal datum | See datum, definition 2. | HDBK-850 |
| horizontal deformation | In relative orientation, the cumulative model warpage affecting the horizontal datum from z-motion error, bridging error, and swing error. | HDBK-850 |
| horizontal direction | Observed horizontal angles at a triangulation station reduced to a common initial direction. | HDBK-850 |
| horizontal domain | A domain that provides information or services to more than one domain. Examples of horizontal domains include communications, graphical user interfaces, and databases. Compare with vertical domain. | S/W Reuse |
| horizontal error | An analyst-derived value pertaining to the distance, usually in feet or meters, between a known geodetic position on the ground and the corresponding position calculated from an image. | USIS 95 |
| horizontal extension | See extension, definition 2. | HDBK-850 |
| horizontal geodetic datum | See horizontal control datum. | HDBK-850 |
| horizontal intensity | The intensity of the horizontal component of the magnetic field in the plane of the magnetic meridian. | HDBK-850 |
| horizontal line | A line perpendicular to the vertical. | HDBK-850 |
| horizontal parallax | 1. (astronomy) The geocentric parallax of a body on the observe''s horizon. This is equal to the angular semidiameter of the Earth as seen from the body. 2. (photogrammetry) See absolute stereoscopic parallax. | HDBK-850 |
| horizontal pass point | See supplemental position. | HDBK-850 |
| horizontal photograph | A photograph taken with the axis of the camera horizontal. | HDBK-850 |
| horizontal plane | 1. A plane perpendicular to the direction of gravity; and plane tangent to the geoid or parallel to such a plane. 2. (surveying) A plane perpendicular to the plumb line within which, or on which, angles and distances are observed. For any planimetric survey it is assumed that all plumb lines therein are parallel, and all horizontal planes therein are parallel. | HDBK-850 |
| horizontal reference datum | (UCDM Entity: "HORIZONTAL-REFERENCE-DATUM") A frame of reference for geodetic latitude and longitude. | USIGS/CDM-A |
| horizontal refraction | A natural error in surveying which is the result of the horizontal bending of light rays between a target and an observing instrument. Usually caused by the differences in density of the air along the path of the light rays, resulting from temperature variations. See also terrestrial refraction. | HDBK-850 |
| horizontal stadia | A method of measuring distances wherein the stadia rod is held in a horizontal position and the stadia hairs of the instrument are vertical during observations. | HDBK-850 |
| horizontal taping and plumbing | A method whereby the tape is held horizontally, and the positions of its pertinent graduations are projectcd to the ground with plumb bobs. | HDBK-850 |
| horizontal/vertical bridging | See bridging. | HDBK-850 |
| horizontal/vertical extension | See extension definition 2. | HDBK-850 |
| horizontalizing the model | See leveling, definition 2. | HDBK-850 |
| horizontally controlled photography | Cartographic aerial photography obtained simultaneously with recording of distance measurements between the taking aircraft and each of two or more geodetically positioned ground stations. Shoran or shiran are normally used as the distance measuring equipment. The result is precise relative horizontal positioning of each photograph which has associated recorded distances. This positioning information is used as horizontal control data in the mapping process. | HDBK-850 |
| Horrebow level attachment | A level used in conjunction with a micrometer in a telescope whereby latitude observations by the Horrebow-Talcott method can be made. | HDBK-850 |
| Horrebow-Talcott method of latitude determination | See latitude determination; zenith-telescope method. | HDBK-850 |
| host | A computer, particularly a source or destination of messages, on a communications network. | TAFIM 3.0 |
| Host Data Base System | A class of information systems that support the exploitation process and maintain databases of imagery-derived reporting and requirements data and other imagery assessment data. | USIS 95 |
| Hostname | Logical name given to a host. [DISA/DO3 (CIO)] | DISA CFS |
| Hot Photographic Interpretation Report | A report that alerts requesters of significant highlights of a particular mission or target. It is not formatted and can be sent via message, telephone, or both. Since it is not formatted, a second message is required. | USIS 95 |
| hot spot | (photography) A small area of undesired brilliancy of illumination in the image projected by a printer or a reader. | HDBK-850 |
| Hotine Oblique Mercator | A mapping projection developed specifically for LANDSAT imagery, dividing the Earth into five zones of latitude. Within each zone, oblique strips corresponding to individual LANDSAT spacecraft paths are projected onto a plane. The axis of projection corresponds approximately to the path of scene centers. | HDBK-850 |
| hour angle | The hour angle of a celestial body is the time elapsed since its upper transit. It is the angle between the observer's (astronomic) meridian and the declination circle of the body, measured positive westward from the meridian. See also Greenwich hour angle; local hour angle; sidereal hour angle. | HDBK-850 |
| hour angle difference | See meridian angle difference. | HDBK-850 |
| hour angle system (of coordinates) | An equatorial system of curvilinear celestial coordinates which has the Equator and the local meridian as primary and secondary reference planes, respectively. The position of a celestial body is given by its hour angle and declination. | HDBK-850 |
| hour circle | Any great circle on the celestial sphere whose plane is perpendicular to the plane of the celestial equator. Also called circle of declination; circle of right ascension. See also celestial meridian; colures. | HDBK-850 |
| hub | 1. A distribution point in a network. 2. A device that accepts a signal from one point and redistributes it to one or more points | FED STD 1037C |
| hub | A temporary traverse station marker, usually of wood. The stake is driven flush with the ground with a tack or small nail on top to mark the exact point of reference for angular and linear measurements. | HDBK-850 |
| Huffman coding | A coding technique used to compact data by representing the more common events with short codes and the less common events with longer codes | FED STD 1037C |
| Hull Integrity Test Site Charts (HITS) | Charts which provide detailed bathymetric and environmental data for submarine test dive areas. | HDBK-850 |
| Human Factors Engineering (HFE) | Approach that makes use of scientific facts in the design of items (i.e., computer systems, software, etc.) to produce effective human-machine integration and utilization. [HCI Style Guide] | DISA CFS |
| human intelligence (HUMINT) | (DOD, NATO) A category of intelligence derived from information collected and provided by human sources. | JPUB 1-02 |
| human system interfaces | The machine integration and interpretation data and its presentation in a form convenient to the human operator; displays; human intelligence emulated in computational devices; and simulation of synthetic environments. | USIS 95 |
| human technology environment | The environment within which people interact with information technology, typically a mouse and windowing system. | OpenGIS Guide |
| human technology interface (HTI) | The interface across which people interact with information technology. The service provided through this interface is access to the information infrastructure and to other people. | OpenGIS Guide |
| human/computer interface (HCI) | The boundary across which physical interaction between a human being and the application platform takes place. | IEEE P1003.0 |
| Huygen's principle | A general principle applying to all forms of wave motion which states that every point on the instantaneous position of an advancing phase front (wave front) may be regarded as a source of secondary spherical wavelets. The position of the phase front a moment later is then determined as the envelope of all of the secondary wavelets (ad infinitum). This principle is extremely useful in understanding effects due to refraction, reflection, diffraction, and scattering of all types of radiation, including sonic radiation as well as electromagnetic radiation and applying even to ocean wave propagation. | HDBK-850 |
| hybrid graphical user interface | A GUI that is composed of toolkit components from more than one user interface style. | JTA 2.0 |
| hybrid tridimensional datum | A tridimensional datum consisting of a horizontal datum and a vertical datum which are defined by two different surfaces. | CEN/TC 287 |
| hydrographic chart | (JCS) A nautical chart showing depths of water, nature of bottom, contours of bottom and coastline, and tides and currents in a given sea or sea and land area. Also called marine map; nautical chart. | HDBK-850 |
| hydrographic datum | The plane of reference of soundings, depth curves, and elevations of foreshore and offshore features. Also called chart datum. See also international low water; low water datum; National Geodetic Vertical datum of 1929; sounding datum; tidal datum. | HDBK-850 |
| hydrographic detail | The features along the shore and the submerged parts of bodies of water. Also called hydrographic feature. | HDBK-850 |
| hydrographic digital data | Data in discrete numerical form derived from the measurements and description of the physical features of the oceans, seas, lakes, rivers and other waters, and their adjoining coastal areas (with particular reference to navigational usage.) | HDBK-850 |
| hydrographic feature | See hydrographic detail. | HDBK-850 |
| Hydrographic Information Handling System (HIHAN) | HIHAN is a software/hardware system under development by the Detachment Stennis Space Center (NRL) which will automate the preprocessing, merging, integration and preparation of hydrographic data from a variety of sources. | HDBK-850 |
| hydrographic reconnaissance | A reconnaissance of an area of water to determine depths, beach gradients, the nature of the bottom, and the location of coral reefs, rocks, shoals, and man-made obstacles. | HDBK-850 |
| hydrographic sextant | See surveying sextant. | HDBK-850 |
| hydrographic sounding | See sounding, definitions 1 and 2. | HDBK-850 |
| hydrographic survey | A survey made in relation to any considerable body of water, such as a bay, harbor, lake, or river for the purposes of determination of channel depths for navigation, location of rocks, sand bars, lights, and buoys; and in the case of rivers, made for flood control, power development, navigation, water supply, and water storage. | HDBK-850 |
| hydrography | 1. (JCS) The science which deals with the measurements and description of the physical features of the oceans, seas, lakes, rivers, and their adjoining coastal areas, with particular reference to their use for navigational purposes. 2. That part of topography pertaining to water and drainage features. | HDBK-850 |
| hydrology | Hydrology in its broadest extent deals with the properties, laws, and phenomena of water; of its physical, chemical, and physiological relations; of its distribution throughout the habitable Earth; and of the effect of this circulation on human lives and interests. | HDBK-850 |
| hydrophone | An electroacoustic transducer that converts sound energy into electrical energy. See also transducer. | HDBK-850 |
| hydrosphere | That part of the Earth that consists of the oceans, seas, lakes, and rivers; a similar part of any other spatial body if such a body exists. Distinguished from the atmosphere and lithosphere. | HDBK-850 |
| hydrostatic equation | In numerical equations, the form assumed by the vertical component of the vector equation of motion when all Coriolis force, Earth curvature, frictional, and vertical acceleration terms are considered negligible compared with those involving the vertical pressure force and the force of gravity. | HDBK-850 |
| hydrostatic equilibrium | The state of a fluid whose surfaces of constant pressure and constant mass (or density) coincide and are horizontal throughout. Complete balance exists between the force of gravity and the pressure force. The relation between the pressure and the geometric height is given by the hydrostatic equation. | HDBK-850 |
| hygrometric | Relating to the relative humidity or comparative amount of moisture in the atmosphere. Since the atmosphere penetrates the pores or cells of material bodies in varying degrees depending upon the substances of which they are composed, the amount of moisture which it contains will affect the shapes and dimensions of certain instruments and equipment used in surveying and mapping. For this reason it is necessary to select materials which are not sensitive to hygrometric conditions for the construction of leveling rods, planetable sheets, etc., and for the construction and printing of maps. | HDBK-850 |
| hygroscopic | The property of materials such as paper and films to absorb or release moisture and, in so doing, to expand or contract. | HDBK-850 |
| hyperbolic line of position | A line of position in the shape of a hyperbola, determined by measuring the difference in distance to two fixed points. Loran lines of position are an example. | HDBK-850 |
| hyperfocal distance | The distance from the camera lens to the nearest object in focus when the camera lens is focused at infinity. | HDBK-850 |
| hyperspectral data | Remotely sensed or in situ data collected at contiguous, narrowband wavelengths for a portion of the electromagnetic spectrum. Most operational systems today typically collect data in the range of 100 to 300 or more bands (channels). | MUG 95 |
| Hyperspectral Digital Imagery Collection Experiment | A program to provide a state-of-the-art imaging spectrometer for the .4 to 2.5 micron region, integrated into an aircraft for use in experiments by civil agencies to evaluate the utility of hyperspectral data for their applications. See Hyperspectral MASINT Support to Military Operations (HYMSMO). | USIS 95 |
| Hyperspectral Image Processing System (HIPS) | A hyperspectral image processing system that has been developed and is being distributed commercially. HIPS was designed and developed specifically to handle hyperspectral image cubes of any number of dimensions and to emphasize spectral processing. The entire cube is treated and spectra and image planes are extracted for more traditional spectrum or image analysis. Spectral libraries are integrated into HIPS and are an integral part of the analysis process. SETS Technology, Inc., is the builder. | USIS 95 |
| hyperspectral imaging sensor | Hyperspectral imaging sensors have 100-200 spectral bands with a spectral resolution delta lamba/lambda (e.g., 0.005 µm in the visible and 0.1 µm in the thermal infrared). The finer spectral resolution available with hyperspectral imaging provides significantly more capability for materials identification. See also hyperspectral sensor, imaging spectrometer. | Anderson 94 |
| Hyperspectral MASINT Support to Military Operations (HYMSMO) | An umbrella program for sponsoring a suite of collection and exploitation experiments, based on MASINT needs, that will be used to assess the utility of HYMSMO, resulting in acquisition recommendations for less complex, inexpensive MASINT prototype development and testing, leading to fielded MASINT systems and applications. | USIS 95 |
| hyperspectral scanner | See imaging spectrometer. | Lillesand 94 |
| hyperspectral sensor | A sensor which collects and records data in hundreds of spectral bands. The increased number of sensor bands provides higher spectral resolution and more opportunities to detect subtle spectral differences in signatures that are too narrow to be differentiated on multispectral imagery. See also imaging spectrometer, hyperspectral imaging sensor. | MUG 95 |
| hyperstereoscopy | (JCS) Stereoscopic viewing in which the relief effect is noticeably exaggerated, caused by the extension of the camera base. Also called appearance ratio; exaggerated stereo; relief stretching; stereoscopic exaggeration. See also vertical exaggeration, definition 1. | HDBK-850 |
| hypertext | Internally cross-referenced written information that allows a user to jump from topic to related topic. Text and pictures can act as links to other places in the same or different documents. | Multimedia |
| Hypertext Markup Language (HTML) | The authoring language used to create documents on the World Wide Web. HTML is similar to SGML, although it is not a strict subset. | PC Webopaedia |
| Hypetext Transfer Protocol (HTTP) | The underlying protocol used by the World Wide Web (WWW). HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. The other main standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed. HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the main reason that it is difficult to implement Web sites that react intelligently to user input. This shortcoming of HTTP is being addressed in a number of new technologies, including ActiveX, Java, JavaScript and cookies. Currently, most Web browsers and servers support HTTP 1.1. One of the main features of HTTP 1.1 is that it supports persistent connections. This means that once a browser connects to a Web server, it can receive multiple files through the same connection. This should improve performance by as much as 20%. | PC Webopaedia |
| hypsograph | An instrument of the slide rule type used to compute elevations from vertical angles and horizontal distances. | HDBK-850 |
| hypsographic detail | The features pertaining to relief or elevation of terrain. | HDBK-850 |
| hypsographic map (or chart) | A map or chart showing land or submarine bottom relief in terms of height above, or below, a datum by any method, such as contours, hachures, shading, or tinting. Also called hypsometric map (or chart). | HDBK-850 |
| hypsography | 1. The science or art of describing elevations of land surfaces with reference to a datum, usually sea level. 2. That part of topography dealing with relief or elevation of terrain. | HDBK-850 |
| hypsometer | An instrument used in determining elevations of points on the Earth's surface in relation to sea level by determining atmospheric pressure through observation of the boiling point (temperature) of water at each point. | HDBK-850 |
| hypsometric map (or chart) | See hypsographic map. | HDBK-850 |
| hypsometric tint scale | A graphic scale in the margin of maps and charts which indicates heights or depths by graduated shades of colors. See also hypsometric tinting. | HDBK-850 |
| hypsometric tinting | (JCS) A method of showing relief on maps and charts by coloring, in different shades, those parts which lie between selected levels. Also called altitude tints; color gradients; elevation tints; gradient tints; layer tints. | HDBK-850 |
| hypsometry | The art of determining, by any method, surface elevations on the Earth with reference to sea level. | HDBK-850 |
Last Updated by Mark Owens 17 February 1999.