Index USIGS Glossary

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Term Definition/Description Source
Pacific Air Forces (PACAF) Interim National Exploitation System (PINES) Self-contained receive, processing, storage and retrieval, exploitation, reporting, and dissemination unit with associated communications management and data base support. USIS 95
packet switching The process of routing and transferring data by means of addressed packets so that a channel is occupied during the transmission of the packet only, and upon completion of the transmission the channel is made available for the transfer of other traffic. FED STD 1037C
packet-switching network A switched network that transmits data in the form of packets. FED STD 1037C
packet-switching node In a packet-switching network, a node that contains data switches and equipment for controlling, formatting, transmitting, routing, and receiving data packets. FED STD 1037C
panchromatic (photography) Sensitive to light of all colors, as a film or plate emulsion. HDBK-850
pancratic system A variable power optical system. Also called zoom system. HDBK-850
panel 1. (cartography) See panel base. 2. (photogrammetry) An element of a target used for control station identification on aerial photography. Panels are made of cloth, plastics, plywood, or Masonite, and are positioned in a symmetrical pattern centered on the station. See also target. HDBK-850
panel base (cartography) The completed assembly of pieces of film positives onto a grid or projection which is used as a base for compilation. Also called film mosaic; panel. HDBK-850
paneling 1. (cartography) Cutting a film positive of a map, in which some distortion is involved, into several pieces and cementing them in place, on a projection constructed on a stable-base medium, in such a way that the error is distributed in small amounts throughout the area rather than being localized. 2. (surveying) The placement of panels on a control station to facilitate station identification on aerial photography. HDBK-850
panoramic camera A camera which takes a partial or complete panorama of the terrain. Some designs utilize a lens which revolves about an axis perpendicular to the optical axis; in other designs, the camera itself is revolved by clockwork to obtain a panoramic field of view. See also frame camera. HDBK-850
panoramic distortion The displacement of ground points from their expected perspective positions, caused by the cylindrical shape of the negative film surface and the scanning action of the lens in a panoramic camera system. HDBK-850
panoramic photograph Photography obtained from a panoramic camera. HDBK-850
pantograph An instrument for copying maps, drawings, or other graphics at a predetermined scale. Pantographs capable of adjustment for several scales are known as fixed ratio pantographs. See also two-dimensional pantograph. HDBK-850
paper-strip method (rectification) A graphical method of making a point-by-point rectification based on the invariance of the cross ratio. A modification of this technique permits map detail to be revised from an oblique aerial photograph based on the projectivity of straight lines. HDBK-850
parallactic aberration See differential aberration. HDBK-850
parallactic angle 1. (astronomy) The angle between a body's hour circle and its vertical circle. Also called position angle. 2. (photogrammetry) Also called angular parallax. See angle of convergence. HDBK-850
parallactic error An error caused by personal or instrument parallax. HDBK-850
parallactic grid (photogrammetry) A uniform pattern of rectangular lines drawn or engraved on some transparent material, usually glass, and placed either over the photographs of a stereoscopic pair or in the optical system of a stereoscope, in order to provide a continuous floating mark system. HDBK-850
parallactic inequality A secondary effect in solar perturbations in the Moon's longitude due to the ellipticity of the Earth's orbit. HDBK-850
parallax 1. (JCS) In photography, the apparent displacement of the position of an object in relation to a reference point due to a change in the point of observation. 2. The apparent displacement between objects on the Earth's surface due to their difference in elevation. Also called angular parallax; want of correspondence. See also absolute stereoscopic parallax; age of parallax inequality; annual parallax; equatorial horizontal parallax; false parallax; geocentric parallax; horizontal parallax; instrument parallax; lunar parallax; residual parallax; solar parallax; y-parallax. HDBK-850
parallax age See age of parallax inequality. HDBK-850
parallax bar See stereometer. HDBK-850
parallax difference The difference in the absolute stereoscopic parallaxes of two points imaged on a pair of photographs. Customarily used in determination of the difference in elevation of objects. HDBK-850
parallax in altitude Geocentric parallax at any altitude. The expression is used to distinguish the parallax at the given altitude from the horizontal parallax when the body is in the horizon. HDBK-850
parallax inequality The variation in the range of tide or in the speed of tidal currents because of the continual change in the distance of the Moon from the Earth. The range of tide and speed of tidal currents tend to increase as the Moon approaches perigee and to decrease as it approaches apogee. HDBK-850
parallel A circle on the surface of the Earth, parallel to the plane of the Equator and connecting all points of equal latitude, or a circle parallel to the primary great circle of a sphere or spheroid; also, a closed curve approximating such a circle. Also called inverse parallel. See also astronomic parallel; ecliptic parallel; fictitious parallel; geodetic parallel; geographic parallel; grid parallel; ground parallel; isometric parallel; oblique parallel; photograph parallel: principal parallel; standard parallel; transverse parallel. HDBK-850
parallel of altitude A circle of the celestial sphere parallel to the horizon connecting all points of equal altitude. Also called almucantar; altitude circle; circle of equal altitude. HDBK-850
parallel of declination A circle of the celestial sphere parallel to the celestial equator. Also called celestial parallel; circle of equal declination. HDBK-850
parallel of latitude See circle of longitude. HDBK-850
parallel plate An optical disk with optically flat, parallel surfaces; used especially in optical micrometers. Also called plane plate. See also optical flat. HDBK-850
parallel sphere The celestial sphere as it appears to an observer at the pole, where celestial bodies appear to move parallel to the horizon. HDBK-850
parameter In general, any quantity of a problem that is not an independent variable. More specifically the term is often used to distinguish from dependent variables quantities which may be assigned arbitrary values for purposes of the problem at hand. HDBK-850
parameter passing mode Describes the direction of information flow for an operation parameter. The parameter passing modes are IN, OUT, and INOUT. CORBA 2.2
parameterize The act or process of describing a geometric situation with a mathematical model containing adjustable constants. HDBK-850
parametric equations A set of equations in which the independent variables or coordinates are each expressed in terms of a parameter. HDBK-850
parametric latitude The angle at the center of a sphere which is tangent to the ellipsoid along the geodetic equator, between the plane of the equator and the radius to the point intersected on the sphere by a straight line perpendicular to the plane of the Equator and passing through the point on the ellipsoid whose parametric latitude is defined. Parametric latitude is an auxiliary latitude used in problems of geodesy and cartography. HDBK-850
paraxial ray A ray whose path lies very near the axis of a lens and which intersects the lens surface at a point very close to its vertex and at nearly normal incidence. HDBK-850
partial tide See constituent. HDBK-850
participating activity The activity responsible for resolving and consolidating coordination comments on standardization program plans within its Military Department or Defense Agency, and submitting those comments to the LSA [Lead Standardization Activity]. [DOD 4120.3-M] DISA CFS
part-of relationship A relationship between two entities or two features in which one is a component of the other. ISO/TC 211
pass 1. A single circuit of the Earth by a satellite. See also orbit. 2. The period of time a satellite is within telemetry range of a data acquisition station. 3. (mensuration) One complete set of pointings or measurements on a specific plate, reseau, or other media containing photographic imagery. HDBK-850
pass The term used to refer to a specific revolution in the course of an imaging day, beginning with pass one and continuing through the last revolution of the same day. USIS 95
pass point A point whose horizontal and/or vertical position is determined from photographs by photogrammetric methods and which is intended for use in the absolute orientation of a model. Also called photogrammetric point. See also annex point; supplemental elevation; supplemental position. HDBK-850
pass verdict A test verdict given when the observed test outcome gives evidence of conformance to the conformance requirement on which the test purpose is focused and is valid with respect to the relevant standard(s) and with respect to the specified statement. ISO/TC 211
passive remote sensing Remote sensing of energy naturally reflected or radiated from the terrain. USIS 95
passive satellite A satellite which contains no power sources to augment output power; a satellite which is a passive reflector. See also active satellite. HDBK-850
patch (digital) A small area of information spliced into a data base or software in order to update, complete, or densify the data content. HDBK-850
path The projection of the orbital plane of the satell'te on the Earth's surface; the locus of the satellite subpoint. HDBK-850
Pathfinder Pathfinder is a process that provides a critical link between commercial and government developers of technologies and the analyst users. With its beginning in Project Beacon (1995) and continuous improvement through Pathfinder 96, 97, and 98, key technologies continue to be identified, evaluated, and recommended for insertion to qualitatively and quantitatively improve the analysts' processes. The ultimate beneficiaries are the many different NIMA customers. NIMA Web Site
PC-1000 camera A trade name for a geodetic stellar camera having a focal length of 1,000 mm. HDBK-850
Peaucellier inversor A class of inversor providing a mechanical solution for the linear and angular elements of rectification. Also called scissors inversor. HDBK-850
Peaucellier-Carpentier inversor A modified Carpentier inversor coupled to the linkage system of a Peaucellier inversor to provide a mechanical means of solving the linear and angular elements of rectification. HDBK-850
peel (negative engraving) A technique of removing the opaque stratum from its supporting base. Peeling between etched outline images produces a negative; peeling outside of the etched outline images produces a positive. See also mask, definition 2. HDBK-850
peepsight alidade A type of alidade consisting of a peep sight mounted on a straightedge. HDBK-850
peepsight compass The sights of a compass formed by standards with slits for a sighting medium rather than a telescope. HDBK-850
peer protocol The protocol governing communications between program entities that have the same function in the same layer in each of two OSI networks. TAFIM 3.0
peg adjustment A method of adjusting a leveling instrument of the dumpy level type, to make the line of collimation parallel with the axis of the spirit level, and employing two stable marks (pegs) the length of one instrument sight apart. Also called 11/10 peg adjustment. HDBK-850
peg test A method of testing the collimation adjustment of a leveling instrument. HDBK-850
Pemberton leveling rod A speaking rod marked with alternate rows of circular and diamond-shaped dots, running diagonally across the rod. Read to hundredths of a foot. HDBK-850
pendulum 1. In general, a body so suspended as to swing freely to and fro under the influence of gravity and momentum. 2. A vertical bar so supported from below by a stiff spring as to vibrate to and fro under the combined action of gravity and the restoring force of the spring. See also compound pendulum; dummy pendulum; free-swinging pendulum; idle pendulum; Invar pendulum; invariable pendulum; Mendenhall pendulum; quartz pendulum; receiver; relative pendulum; reversible pendulum; simple pendulum; working pendulum. HDBK-850
pendulum alidade A telescopic alidade in which a pendulum device replaces the conventional bubble for establishing a horizontal reference line from which vertical angles may be measured. HDBK-850
pendulum astrolabe An astronomic instrument using a constant altitude for position determination. Its distinctive feature is a mirror suspended on top of a pendulum to form the artificial horizon. HDBK-850
pendulum level A leveling instrument in which the line of sight is automatically maintained horizontal by means of a built-in pendulum device. Also called automatic level. HDBK-850
percent of slope See gradient. HDBK-850
performance A measure of a computer system or subsystem to perform its functions; for example, response time, throughput, number of transactions per second. The efficiency of a system in accomplishing pieces of work is an attribute of performance. IEEE P1003.0
Performance Goal A Performance Goal is defined as a target level of performance and is expressed as a tangible, measurable objective, by which actual achievement or performance can be measured or compared. A performance goal is expressed as a quantitative rate, value or standard. [DISA/D5] DISA CFS
performance requirement A requirement that specifies a performance characteristic that a system or system component must possess; for example, speed, accuracy, frequency. IEEE P1003.0
periapsis See pericenter. HDBK-850
periastron That point of the orbit of one member of a double star system at which the stars are nearest together. Opposite of apastron. HDBK-850
pericenter In an elliptical orbit the point in the orbit which is the nearest distance from the focus where the attracting mass is located. The pericenter is at one end of the major axis of the orbital ellipse. Opposite of apoapsis; apocenter; apofocus. Also called periapsis; perifocus. HDBK-850
pericynthion See perilune. HDBK-850
perifocus See pericenter. HDBK-850
perigee The point at which a satellite orbit is the least distance from the center of the gravitational field of the earth. Opposite of apogee. HDBK-850
perigee-to-perigee period See anomalistic period. HDBK-850
perihelion The point in the elliptical orbit of a planet which is the nearest to the Sun, when the Sun is the center of attraction. Opposite of aphelion. HDBK-850
perilune The point of closest approach of an orbiting body to the Moon. Opposite of aplune; apocynthion. Also called pericynthion. HDBK-850
period 1. The interval needed to complete a cycle. 2. The interval between passages at a fixed point of a given phase of a simple harmonic wave; the reciprocal of frequency. See also anomalistic period; nodical period; orbital period; sidereal period; synodic period. HDBK-850
period Duration of time specified by its beginning and end points. [ISO 8601:1988] ISO/TC 211
period of satellite See orbital period. HDBK-850
periodic errors In a complete set of observations there corresponds to every individual error another error which is necessarily more or less equal and opposite. In a limited series the cancellation may not be quite exact, but the error of the mean of n observations may be expected to be 1/n of that of a single measure, or less. HDBK-850
periodic intelligence summary A report of the intelligence situation in a tactical operation, normally produced at Corps level or its equivalent, and higher, usually at intervals of 24 hours, or as directed by the commander. USIS 95
periodic perturbations Perturbations to the orbit of a planet or satellite which change direction in regular or periodic fashion in time, such that the average effect over a long period of time is zero. HDBK-850
periodic terms In the mathematical expression of an orbit, terms which vary with time in both magnitude and direction. HDBK-850
periodic time Tthe time of one cycle. [ISO 31-2:1992] ISO/TC 211
periodicity The frequency with which a target is due to be collected. USIS 95
permanent bench mark (PBM) A bench mark of as nearly permanent character as it is practicable to establish. Usually designated simply as a bench mark or BM. A permanent bench mark is intended to maintain its elevation with reference to an adopted datum without change over a long period of time. Also called monumented bench mark. HDBK-850
permission A prescription that a particular behavior is allowed to occur. A permission is equivalent to there being no obligation for the behavior not to occur. RM-ODP
perpendicular A perpendicular line, plane, etc. A distinction is sometimes made between perpendicular and normal, the former applying to a line at right angles to a straight line or plane, and the latter referring to a line at right angles to a curve or curved surface. HDBK-850
perpendicular equation (traverse) A condition equation to reduce to zero the algebraic sum of the projections of the separate lines of a traverse upon perpendiculars to a fixed line with which the traverse forms a closed figure. HDBK-850
persistence The property that an object continues to exist across changes of contractual context of an epoch. RM-ODP
Persistence Transparency A distribution transparency which masks, from an object, the deactivation and reactivation of other objects (or itself). Deactivation and reactivation are often used to maintain the persistence of an object when the system is unable to provide it with processing, storage, and communication functions continuously. RM-ODP
persistent object An object that can survive the process or thread that created it. A persistent object exists until it is explicitly deleted. CORBA 2.2
personal equation The time interval between the sensory perception of a phenomenon and the motor reaction thereto. A personal equation may be either positive or negative, as an observer may anticipate the occurrence of an event, or wait until he actually sees it occur before making a record. This is a systematic error, treated as the constant type. HDBK-850
personal error An error caused 'y an individual's personal habits, his inability to perceive or measure dimensional values exactly, or by his tendency to react mentally and physically in a uniform manner under similar conditions. It may be a systematic error, if it occurs regularly or a blunder if it occurs once. A certain amount of minor personal error can be included with random errors. HDBK-850
personal parallax See instrument parallax, definition 2. HDBK-850
perspective The appearance to the eye of objects in respect to their relative distance and position. HDBK-850
perspective axis See axis of homology. HDBK-850
perspective center The point of origin or termination of bundles of perspective rays. The two such points usually associated with a survey photograph are the interior perspective center and the exterior perspective center. In a perfect lens-camera system, perspective rays from the interior perspective center to the photographic images enclose the same angles as do the corresponding rays from the exterior perspective center to the objects photographed. In a lens having distortion, this is true only for a particular zone of the photograph. In a perfectly adjusted lens-camera system, the exterior and interior perspective centers correspond, respectively, to the front and rear nodal points of the camera lens. Also called center of projection. HDBK-850
perspective chart A chart on a perspective projection. HDBK-850
perspective drawing A line drawing showing several different views of a scene, a geometrical projection of an object on a plane perpendicular to the horizon, a technical presentation on a plane or curved surface of the spatial relationships of objects as they appear to the eye and give the impression of distance. USIS 95
perspective grid (JCS) A network of lines, drawn or superimposed on a photograph, to represent the perspective of a systematic network of lines on the ground or datum plane. Also called Canadian grid. See also grid method. HDBK-850
Perspective Image Generation & Exploitation A DIA image perspective transformation system. USIS 95
perspective map projection A map projection produced by straight lines radiating from a selected point and passing through poi'ts on the earth's surface to the projection surface. Also called geometric map projection. HDBK-850
perspective plane Any plane containing the perspective center. The intersection of a perspective plane and the ground will always appear as a straight line on an aerial photograph. HDBK-850
perspective projection The projection of points by straight lines drawn through them from some given point to an intersection with the plane of projection. Unless otherwise indicated, the point of projection is understood to be at a finite distance from the plane of projection. HDBK-850
perspective ray A line joining a perspective center and a point object. See also image ray. HDBK-850
perspective spatial model Optical reconstruction of an area of terrain showing depth by viewing a pair of aerial photographs through a stereoscope. HDBK-850
perspective view A three-dimensional representation generated with a reference to a specific viewer location on or above the surface portrayed. HDBK-850
perspectivity The correspondence between the points, lines, or planes of two geometric configurations in perspective. Usually referred to as linear perspectivity because the true perspective center must be recoverable before angular perspectivity can be included. HDBK-850
perturbation In celestial mechanics, differences of the actual orbit from a central force orbit, arising from some external force such as a third body attracting the other two; a resisting medium (atmosphere); failure of the parent body to act as a point mass, and so forth. See also gravitational perturbations; long period perturbations; lunisolar perturbations; nongravitational perturbations; periodic perturbations; secular perturbations; short period perturbations; terrestrial perturbations. HDBK-850
perturbed orbit The orbit of a satellite differing from its normal orbit due to various disturbing effects such as nonsymmetrical gravitational effects, atmospheric drag, radiation pressure, and so forth. See also perturbation. HDBK-850
perturbing factors (forces) In celestial mechanics, any force that acts on the orbiting body to change its orbit from a central force orbit. HDBK-850
phase 1. (general) Of a periodic quantity, for a particular value of the independent variable, the fractional part of a period through which the independent variable has advanced, measured from an arbitrary reference. 2. (surveying) The apparent displacement of an object or signal caused by one side being more strongly illuminated than the other. The resultant error in pointing is similar to the error caused by observing an eccentric signal. 3. (astronomy) A stage in a cycle of recurring aspects, caused by a systematic variation of the illumination of an object. The Moon passes through its phases, new Moon to full Moon and back to new Moon, as its position relative to the Sun and Earth changes. HDBK-850
phase age See age of phase inequality. HDBK-850
phase angle 1. The phase difference of two periodically recurring phenomena of the same frequency, expressed in angular measure. 2. The angle at a celestial body between the Sun and Earth. HDBK-850
phase inequality Variations in the tide or tidal currents associated with changes in the phase of the Moon. At new and full Moon (springs) the tide-producing forces of the Sun and Moon act in conjunction, resulting in greater than average tide and tidal currents. At first and last quarters of the Moon (neaps) the tide-producing forces oppose each other, resulting in smaller than average tide and tidal currents. HDBK-850
phenomenon A fact, occurrence or circumstance. EXAMPLE - Route 10; George Washington National Forest; Chesterfield County. ISO/TC 211
Philadelphia leveling rod A two-piece target rod, with graduation marks so styled that it may also be used as a speaking rod. For heights greater than 7 feet the target is clamped at 7 feet, and raised by extending the rod. As a target rod, it is read by vernier to thousandths of a foot; as a speaking rod, to half-hundredths of a foot. HDBK-850
photo altitude Height of an aircraft above the mean elevation of the terrain to be photographed. HDBK-850
photo index 1. An index map made by assembling the individual aerial photographs into their proper relative positions and copying the assembly photographically at a reduced scale. Also called index to photography; photo plot; plot map. 2. See sortie plot. HDBK-850
photo plot See photo index, definition 1. HDBK-850
photo pyramid A component of an analytical method of precise determination of photographic tilt which represents a specific spatial configuration formed by three control points of known position on the photograph (forming a triangle) and the exposure station. When used with the ground pyramid, it permits the exact position of the exposure station to be determined and, by analytical techniques, the exact tilt of the photograph. See also ground pyramid. HDBK-850
photo revision The process of making changes on a map based upon information obtained from a study of aerial photographs. HDBK-850
photo scale See scale, definition 1. HDBK-850
photoalidade A photogrammetric instrument having a telescopic alidade, a plateholder, and a hinged ruling arm mounted on a tripod frame. It is used for plotting lines of direction and measuring vertical angles to selected features appearing on oblique and terrestrial photographs. HDBK-850
photoangulator See angulator. HDBK-850
photobase The distance between the principal points of two adjacent prints of a series of vertical aerial photographs. It is usually measured on one print after transferring the principal point of the other print. See also base line, definition 2. HDBK-850
photocompose To mechanically impose one or more images by step-and-repeat exposures in predetermined positions on a press plate or negative by means of a photocomposing machine. HDBK-850
photocontour map Essentially, a topographic map upon which the planimetric detail is depicted photographically in its correct position. It is usually prepared from convergent photography although conventional vertical photography can be used. HDBK-850
photocontour process A process developed to combine, in a photocontour map, that information normally portrayed on a topographic drawing and an aerial photograph. The system usually is composed of three elements: (1) a conventional stereoplotter for contouring; (2) a rectifier for tilt rectification of the aerial photographs; and (3) a zone printer to eliminate relief displacement. It is designed to utilize convergent photographs although normal vertical photographs can be utilized as well. HDBK-850
photocontrol base See control base. HDBK-850
photocontrol diagram Any selected base map or photo index on which proposed ground control networks, to include proposed positions for pass points, are delineated. See also photocontrol index map. HDBK-850
photocontrol index map Any selected base map or photo index on which ground control and photo identified ground points are depicted and identified. See also photocontrol diagram. HDBK-850
photocontrol point See picture control point. HDBK-850
photogoniometer An instrument for measuring angles from the true perspective center to points on a photograph. HDBK-850
photogrammetric camera A general term applicable to any camera used in any of the several branches of photogrammetry. HDBK-850
photogrammetric compilation See compilation, definition 2. HDBK-850
photogrammetric control (JCS) Control established by photogrammetric methods as distinguished from control established by ground methods. Also called minor control; multiplex control. HDBK-850
photogrammetric control point A horizontal control point which has been established by photogrammetric triangulation. HDBK-850
photogrammetric map A topographic map produced from aerial photographs and geodetic control data by means of photogrammetric instruments. Also called stereometric map; stereotopographic map. HDBK-850
photogrammetric point See pass point. HDBK-850
photogrammetric pyramid An analytical method for the precise determination of photographic tilt, consisting of a ground pyramid and a photo pyramid, which represent a spatial configuration formed by three control points of known position on the photograph (forming a triangle) and the exposure station. See also ground pyramid; photo pyramid. HDBK-850
photogrammetric rectification See rectification. HDBK-850
photogrammetric survey A survey utilizing either terrestrial or aerial photographs. HDBK-850
photogrammetric triangulation See phototriangulation. HDBK-850
photogrammetrically digitized Digitized from aerial photographs and geodetic control data by means of photogrammetric instruments, providing three-dimensional coordinates. HDBK-850
photogrammetry 1. (JCS) The science or art of obtaining reliable measurements from photographic images. 2. The preparation of charts and maps from aerial photographs using stereoscopic equipment and methods. See also aerial photogrammetry; analytical photogrammetry; stereophotogrammetry; terrestrial photogrammetry. HDBK-850
photogrammetry The science of mensuration and geometric adjustment of, an aerial photograph or satellite image. Photogrammetry requires: a mathematical model of the image formation process, computation of the internal geometry of an image, and subsequent correction of imagery based upon the ground relationship for every part of the image. Correction of imagery based on computational algorithms and measurement of geometrical position in an image. OGC RFI
photogrammetry Use of aerial photographs to produce planimetric and topographic m'ps of the earth's surface and of features of the built environment. Effective photogrammetry makes use of ground control by which aerial photographs are carefully compared and registered to the locations and characteristics of features identified in ground-level surveys. OpenGIS Guide
photograph A general term for a positive or negative picture made with a camera on sensitized material, or prints from such a camera original. See also aerial photograph; annotated photograph; equivalent vertical photograph; homologous photographs; horizon photograph; horizontal photograph; molded aerial photograph; multiple-lens photograph; oblique air photograph; orthophotograph; panoramic photograph; pinpoint photograph; terrestrial photograph; vertical photograph; wing photo-graph. HDBK-850
photograph Imagery of a scene formed by the reaction of electromagnetic energy on a photosensitive surface. USIS 95
photograph center The center of a photograph as indicated by the images of the fiducial mark(s) of the camera. In a perfectly adjusted camera, the photograph center and the principal point are identical. HDBK-850
photograph coordinates A system of coordinates, either rectangular or polar, describing the position of a point on a photograph. HDBK-850
photograph meridian The image on a photograph of any horizontal line in the object space which is parallel to the principal plane. Since all such lines meet at infinity, the image of the meeting point is at the intersection of the principal line and the horizon trace and all photograph meridians pass through that point. HDBK-850
photograph nadir The point at which a vertical line through the perspective center of the camera lens pierces the plane of the photograph. Also called nadir point; photographic plumb point; plumb point. HDBK-850
photograph parallel The image on a photograph of any horizontal line in the object space which is perpendicular to the principal plane. All photograph parallels are perpendicular to the principal line. HDBK-850
photograph perpendicular The perpendicular from the interior perspective center to the plane of the photograph. HDBK-850
photograph plane The plane in the camera in which the plate or film is held. It is not exactly the primary focal plane of the lens, but is a plane placed so as to secure the best balance of sharp focus on all parts of the plate or film. Also called image plane. HDBK-850
photograph plumb point See photograph nadir. HDBK-850
photographic coverage (JCS) The extent to which an area is covered by photography from one mission or a series of missions or in a period of time. Coverage in this sense conveys the ideal of availability of photography and is not a synonym for the word photography. HDBK-850
photographic datum The effective datum for each photograph. It is a horizontal plane at the average elevation of the terrain, on which distances measured will be at the average scale of the photograph. HDBK-850
photographic exposure The time of exposure multiplied by irradiance or illuminance. HDBK-850
photographic interpretation The examination of photographic images for the purpose of identifying objects and deducing their significance. Also called photointerpretation. See also imagery interpretation. HDBK-850
photographic reading (JCS) The simple recognition of natural or man-made features from photographs not involving imagery interpretation techniques. HDBK-850
photographic reduction The production of a negative, diapositive, or print at a scale smaller than the original. HDBK-850
photographic scale (JCS) The ratio of a distance measured on a photograph or mosaic to the corresponding distance on the ground, classified as follows: very large-scale-1:4,999 and larger; large-scale - 1:5,000 to 1:9,999; medium-scale - 1:10,000 to 1:24,999; small-scale - 1:25,000 to 1:49,999; very small-scale - 1:50,000 and smaller. See also scale. HDBK-850
photographic survey A survey accomplished from either aerial photographs or terrestrial photographs, or from a combination of both. HDBK-850
photographic zenith tube (PZT) The most precise instrument for meridian observations. No corrections are required for level, azimuth, collimation, or flexure. Each observation gives a measure of both the time and the latitude. HDBK-850
photography The art or process of producing images on sensitized material through the action of light. The term photography is sometimes incorrectly used in place of the term photographs. See also analytical photography; composite air photography; continuous strip photography; control point photography; convergent photography; cross-flight photography; direct photography; fan camera photography; horizontally controlled photography; indirect photography; inertial reference photography; lorop photography; mapping photography; metric photography; multiband photography; positional camera photography; process photography; radar photography; radarscope photography; reconnaissance photography; shoran controlled photography; split vertical photography; supplemental photography; terrain profile photography; tricamera photography. HDBK-850
photoidentification (surveying) The detection, identification, and marking of ground survey stations on aerial photographs. Positive identification and location is required if survey data are to be used to control photogrammetric compilation. Also called control-station identification. HDBK-850
photointerpretation See photographic interpretation. HDBK-850
photointerpretation key Reference materials designed to facilitate rapid and accurate identification and the determination of the significance of objects or conditions from an analysis of their photo images. HDBK-850
photointerpretometer A device, used in conjunction with a pocket stereoscope, for making vertical and horizontal measurements. HDBK-850
photolithography A lithographic process in which photographic products are used to produce an image on the printing surface. See also lithography; offset lithography. HDBK-850
photomap (JCS) A reproduction of a photograph or photomosaic upon which the grid lines, marginal data, contours, place names, boundaries, and other data may be added. HDBK-850
photomap backup A photomap printed on the back of a line map of the same area and at the same scale. HDBK-850
photomapping The process of making maps or charts from various types of photographs, with reference to other source maps, charts, or surveys. HDBK-850
photomechanical Pertaining to or designating any reproduction process by a combination of photographic and mechanical operations. HDBK-850
photorevised map A topographic or planimetric map which has been revised by photoplanimetric methods. HDBK-850
photosphere The intensely bright portion of the Sun visible to the unaided eye. HDBK-850
phototheodolite A ground surveying instrument combining a survey camera and a transit; used for measuring the angular orientation of the camera at the moment of exposure. Also called camera transit. HDBK-850
phototopography The science of surveying in which the detail is plotted entirely from photographs taken at suitable ground stations. See also terrestrial photogrammetry. HDBK-850
phototriangulation The process for the extension of horizontal and/or vertical control whereby the measurements of angles and/or distances on overlapping photographs are related into a spatial solution using the perspective principles of the photographs, Generally, this process involves using aerial photographs and is called aerotriangulation, aerial triangulation, or photogrammetric triangulation. See also analytical nadir-point triangulation; analytical phototriangulation; analytical radial triangulation; Arundel method; bridging; cantilever extension; direct radial triangulation; extension of control; graphical radial triangulation; hand-templet triangulation; isocenter triangulation; mechanical templet triangulation; nadir-point triangulation; radial triangulation; slotted-templet triangulation; spider-templet triangulation; stereotemplet triangulation; stereotriangulation; strip radial triangulation; templet method. HDBK-850
phototrig traverse A vertical-angle traverse employing phototrig methods; a procedure for determining elevations trigonometrically, wherein horizontal distances are determined photo- grammetrically and vertical angles are either measured instrumentally in the field, or are obtained from measurements on terrestrial photographs. HDBK-850
phototypesetter A type setting unit comprising two separate and independent units, the keyboard unit and the photographic unit. Composition is accomplished at the keyboard unit, essentially an electric typewriter, which produces a typewritten proof copy and a perforated tape. The tape is then fed at any convenient time thereafter to the photographic unit which produces a right-reading film positive suitable for stickup work. HDBK-850
physical characteristic (target) The visible material aspects of a target or installation, including, but not limited to, dimensions, structural materials, predominant height, configuration, and orientation of its various components such as buildings, structures, runways, and associated facilities and services. HDBK-850
physical data model (PDM) A data model that represents the implementation of the data contained in a data structure. [IEEE 610.5] Compare to conceptual data model (CDM) and logical data model (LDM). IEEE 610-1990
physical geodesy See gravimetric geodesy. HDBK-850
physical layer The first layer of the OSI Reference Model. It governs hardware connectors and byte-stream encoding for transmission. It is the only layer that involves a physical transfer of information between network nodes. TAFIM 3.0
physical view The physical viewpoint represents the overall structu'e of the system's implementation. It shows the system in terms of physically identifiable components and their connectors. IEEE 1471
physiographic pictorial map A map with relief depicted by the systematic application of a standardized set of conventional pictorial symbols, based on the simplified appearance of the physical features they represent, as viewed obliquely from the air at an angle of about 45°. HDBK-850
piano-wire tape Piano wire used instead of a metallic ribbon tape when it is advisable to control hydrography by precise traverse rather than by a weak extension of triangulation, HDBK-850
pictochrome process The process employed to produce pictomaps. Consists of three tonal separations photographically extracted from a photomosaic, blockout masks, drafted symbols, and names data. HDBK-850
pictogram A map of distributions, especially commodities in which small pictorial representative symbols (e.g., sacks, bricks, barrels) are located over the area of production. HDBK-850
pictoline process A photographic masking process utilizing a rotating vacuum frame to produce an edge-enhanced line image from a continuous tone image. HDBK-850
pictomap (JCS) A topographic map in which the photographic imagery of a standard mosaic has been converted into interpretable colors and symbols by means of a pictomap process. See also pictochrome process. HDBK-850
pictorial symbolization (JCS) The use of symbols which convey the visual character of the features they represent. HDBK-850
pictotone process A photo- lithographic method from which film for reproduction and transfer to printing plates is derived for the printing of monochrome photomaps and pictomaps. The process provides a random granular-like effect which visibly sharpens the definition of features and separation of tones, and, in many instances, is superior to halftone printing. HDBK-850
picture control points Supplementary horizontal and vertical control points that are required for the immediate control of mapping operations in a given area. These points are established by field survey parties in specific locations and are precisely identified on the aerial photographs for the project. Also called photocontrol point; picture point. HDBK-850
picture element (pixel) See pixel. [IEEE 610.4] IEEE 610-1990
picture plane A plane upon which can be projected a system of lines or rays from an object to form an image or picture. In perspective drawing, the system of rays is understood to converge to a single point. In photogrammetry, the photograph is the picture plane. HDBK-850
picture point See control point; picture control points. HDBK-850
pilot See sailing directions. HDBK-850
pilot chart Special charts, covering the oceans of the world for each month of the year, issued on one sheet for 3 months at a time on a quarterly basis. They show meteorologic, oceanographic, and hydrographic data for use in conjunction with conventional charts. Timely articles of professional interest to the seafarer are published on the backs. HDBK-850
pilot sheet A sample of a new series, made as a trial in anticipation of a map series, to disclose the problems which occur in the various stages of compilation, drafting, and reproduction. It is later used as a guide in developing the series. Also called prototype. See also experimental map. HDBK-850
pilot's trace (JCS) A rough overlay to a map made by the pilot of a photographic reconnaissance aircraft during or immediately after a sortie. It shows the location, direction, number, and order of photographic runs made, together with the camera(s) used on each run. HDBK-850
pin (surveying) A metal pin used for marking taped measurements on the ground. A set consists of 11 pins. Also called chaini'g pin; surveyor's arrow; taping arrow; taping pin. See also turning point pin. HDBK-850
pinholes Tiny clear spots on negative images caused by dust, air bubbles, or undissolved chemicals. HDBK-850
pinpoint photograph (JCS) A single photograph or a stereopair of a specific object or target. HDBK-850
pinpoint target (JCS) In artillery and naval gunfire support, a target less than 50 meters in diameter. See also area target; precise installation position. HDBK-850
pitch 1. (JCS) The rotation of an aircraft or ship about its lateral axis. 2. (JCS) In air photography, the camera rotation about the transverse axis of the aircraft. 3. (photogrammetry) A rotation of the camera, or of the photograph coordinate system, about either the photograph y-axis or the exterior y-axis. In some photogrammetric instruments and in analytical applications, the symbol phi (f) may be used. Also called longitudinal tilt; tip (which is an obsolete term); y-tilt. HDBK-850
pixel (PIX [picture] Element) The smallest element on a video display screen. A screen is broken up into thousands of tiny dots, and a pixel is one or more dots that are treated as a unit. A pixel can be one dot on a monochrome screen, three dots (red, green and blue) on color screens, or clusters of these dots. Freedman 1995
pixel A picture element, smallest unit of information in a grid cell map or scanner image. Also known as PEL. HDBK-850
pixel In image processessing, the smallest element of a digital image that can be assigned a gray level. Note: This term originated as a contraction for "picture element". Syn: pel; picture element; resolution cell. [IEEE 610.4] IEEE 610-1990
pixel A 2-dimensional picture element that is the smallest nondivisible element of a digital image. ISO/TC 211
pixelization The appearance of individual pixels in an image scene, that determines the limit of image quality. USIS 95
place See position, definition 2. HDBK-850
place name See toponym. HDBK-850
plain attribute An attribute that has a domain that is defined as a simple type in the EXPRESS language. CEN/TC 287
plan position indicator (PPI) 1. (JCS) A cathode-ray tube on which radar returns are so displayed as to bear the same relationship to the transmitter as the objects giving rise to them. 2. A cathode-ray indicator in which a signal appears on a radial line. Distance is indicated radially and bearing as an angle. HDBK-850
plan range (JCS) In air photographic reconnaissance, the horizontal distance from the point below the aircraft to an object on the ground. HDBK-850
planar extent The horizontal extent of a dataset. CEN/TC 287
planar graph A representation of node, link and chain objects as though they occur upon a planar surface. NOTE - Not more than one node may exist at any given point on the surface. Links or chains may only intersect at nodes. See also Level 2 topology. ISO/TC 211
plane See astronomic meridian plane; basal plane; collimation plane; epipolar plane; focal plane; geodetic meridian plane; ground plane; hill plane; horizontal plane; meridional plane; nodal plane; orbital plane; perspective plane; photograph plane; picture plane; principal plane; tangent plane; vertical plane. HDBK-850
plane coordinates See plane rectangular coordinates. HDBK-850
plane curve See plane elliptical arc. HDBK-850
plane elliptical arc Any part of the line formed by the intersection of a plane and an ellipsoid. Also called plane curve. HDBK-850
plane parallel plate See parallel plate. HDBK-850
plane polar coordinates A system of polar coordinates in which the points all lie in one plane. In the terminology of analytical geometry, the distance from the origin to the point is the magnitude of the radius vector and the polar distance is the vectorial angle. HDBK-850
plane rectangular coordinates A system of coordinates in a horizontal plane, used to describe the positions of points with respect to an origin. Also called plane coordinates. HDBK-850
plane survey A survey in which the surface of the Earth is considered a plane. For small areas, precise results may be obtained with plane-surveying methods, but the accuracy and precision of such results will decrease as the area surveyed increases in size. HDBK-850
planet A celestial body of the solar system revolving around the Sun in a nearly circular orbit, or a similar body revolving around a star. See also asteroid; inferior planets; inner planets; major planets; navigational planets; outer planets; principal planets; superior planets; terrestrial planet. HDBK-850
planetable A field device for plotting the lines of a survey directly from observations. It consists essentially of a drawing board mounted on a tripod, with a leveling device designed as part of the board and tripod. See also alidade; Philadelphia leveling rod; stadia. HDBK-850
planetable map A map compiled by planetable methods. The term includes maps made by complete field mapping on a base projection and field contouring on a planimetric base map. HDBK-850
planetable traverse A graphical traverse accomplished by planetable methods. HDBK-850
planetary aberration The angular displacement of the geometric direction between the object and the observer at the instant of light emission, from the geometric direction at the instant of observation. HDBK-850
planetary configurations Apparent positions of the planets relative to each other and to other bodies of the solar system, as seen from the Earth. HDBK-850
planetary geometry 1. Mathematical treatment of the shape and figure of a planet. 2. Mathematical treatment of relationships between two or more planets and/or their orbits. HDBK-850
planetary precession That component of general precession caused by the effect of other planets on the equatorial protuberance of the Earth, producing an eastward motion of the equinoxes along the ecliptic. HDBK-850
planetoid See asteroid. HDBK-850
planimeter A mechanical integrator for measuring the area of a plane surface. See also polar planimeter. HDBK-850
planimetric The horizontal (x,y) locations of non-topographic features, such as rivers, lakes, buildings, roads, etc. USIS 95
planimetric map (JCS) A map representing only the horizontal position of features. Also called line map. See also topographic map. HDBK-850
planimetric-base map A map prepared from aerial photographs by photogrammetric methods, as a guide or base for contouring. HDBK-850
planimetry 1. The science of measuring plane surfaces; horizontal measurements. 2. Parts of a map which represent everything except relief; that is, works of man, and natural features such as woods and water. HDBK-850
planisphere A representation, on a plane, of the celestial sphere, especially one on a polar projection, with means provided for making certain measurements such as altitude and azimuth. Also, a map representation, on a plane, of the Earth's sphere. HDBK-850
planispheric astrolabe An astrolabe consisting of a full graduated circle with a centrally mounted alidade and accessory adjustable plates on which are engraved stereographic projections of the heavens and of the sphere for local latitudes. HDBK-850
planning and direction Establishing the command relationships between all intelligence elements within the joint force and identifying, prioritizing, and validating intelligence and intelligence system requirements. JPUB 2-0
planning chart A chart designed specifically for planning flight operations. HDBK-850
planning map Small-scale military map used for general planning purposes. HDBK-850
Planning Terrain Analysis Data Base (PTADB) A 1:250,000 scale hardcopy, geographic information system consisting of a set of selected single thematic terrain information overlays. HDBK-850
Planning, Programming, and Budgeting System (PPBS) DoD budgetary system for tactical intelligence and related activities (TIARA) funds. USIS 95
plastic block The block of bonded cellulose acetate sheets, each sheet equal in thickness to the contour interval at the scale of the relief model, from which the terrain base is cut. Also called laminate. HDBK-850
plastic relief map A topographic map printed on plastic and molded into a three-dimensional form. The plastic medium is generally formed by heat and vacuum over a terrain model to achieve the three-dimensional representation. HDBK-850
plat A diagram drawn to scale showing land boundaries and subdivisions, together with all data essential to the description and identification of the several units shown thereon, and including one or more certificates indicating due approval. A plat differs from a map in that it does not necessarily show additional cultural, drainage, and relief features. See also cadastral map. HDBK-850
plate 1. (lithography) A thin metal, plastic, or paper sheet, that carries the printing image and whose surface is treated to make only the image areas ink receptive. Also called press plate. See also color plate; combination plate. 2. (photography) A transparent medium, usually glass, coated with a photographic emulsion. See also diapositive; stellar plate. HDBK-850
plate coordinates The x- and y-coordinates of control points appearing on a photographic plate. HDBK-850
plate level A spirit level attached to the plate of a surveying instrument for leveling the graduated circle or, indirectly, making the vertical axis truly vertical. HDBK-850
plate reduction Scaling of control point images on a stellar plate. HDBK-850
platform (A&D LDM Entity: "PLATFORM") A commercial collection platform. A&D LDM
platform A system that is a physical structure that hosts systems or systems components. Note: A kind of system element in the CADM. C4ISR AF
platform The vehicle that holds a sensor. It is usually a satellite, but may be a plane or a helicopter. Sensors can be mounted on tripods for certain uses, such as examining electromagnetic radiation from various types of vegetation. HDBK-850
platform Another term for computer hardware, including microcomputers, workstations, and mainframe computers, or for underlying software, like an operating system, that provides services to layered software. When discussing software, platform independence implies the software can be run on any computer. OpenGIS Guide
platform The entity of the Technical Reference Model that provides common processing and communication services that are provided by a combination of hardware and software and are required by users, mission area applications, and support applications. TAFIM 3.0
platform The objects, structure, vehicle, or base upon which a remote sensor is mounted. USIGS/CDM-A
platform internal interface (PII) The interface between application platform service components within that platform. IEEE P1003.0
platform profile A profile whose focus is on functionality and interfaces for a particular type of platform, which may be a single processor shared by a group of applications or a large distributed system with each application dedicated to a single processor. IEEE P1003.0
platform, imagery The space, air, land, or seaborne host for imagery sensors (e.g., "U2-R", "C-130"). USIS 95
Platonic year See great year. HDBK-850
plot (JCS) 1. A map, chart, or graph representing data of any sort. 2. To represent on a diagram or chart the position or course of a target in terms of angles and distances from known positions; locate a position on a map or chart. 3. The visual display of a single geographical location of an airborne object at a particular instant of time. 4. A portion of a map or overlay on which are drawn the outlines of the areas covered by one or more photographs. See also master plot. HDBK-850
plot map See photo index. HDBK-850
PLOTSHEET Imagery exploitation reporting tool that is a gateway for data input on precise reporting locations of ships, aircraft, etc., into an imagery exploitation support data base. USIS 95
plotting chart 1. (JCS) A chart designed for the graphical processes of navigation. 2. A chart designed primarily for plotting and dead reckoning or lines of position from celestial observations or radio aids. Relief, culture, and drainage are shown as necessary. HDBK-850
plotting scale The relationship of the size of the compilation to the size of the ground area it represents. HDBK-850
plug and play {DII COE} The ability for a COE-derived system to be scaled by the addition/removal of hardware or software components. To have the property of "plug and play," the system must be able to reconfigure itself automatically after component addition/removal with required human intervention limited to no more than a system power down or reboot. DII COE IRTS
plumb bob A conical device, usually of brass and suspended by a cord, by means of which a point can be projected vertically into space over relatively short distances. HDBK-850
plumb line 1. The line of force in the geopotential field. The continuous curve to which the direction of gravity is everywhere tangential. 2. A cord with a plumb bob at one end for determining the direction of gravity. HDBK-850
plumb point See photograph nadir. HDBK-850
plunge See transit, definition 3. HDBK-850
plus angle See angle of elevation. HDBK-850
plus declination See declination, definition 3. HDBK-850
plus distance Fractional part of 100 feet used in designating the location of a point on a survey line as "4 + 47.2," meaning 47.2 feet beyond Station No. 4 or 447.2 feet from the initial point, measured along a specified line. See also plus station. HDBK-850
plus point An intermediate point on a traverse course located by a plus distance from the beginning of the course. HDBK-850
plus sight See backsight. HDBK-850
plus station An intermediate point on a traverse, not at an even tape length distance from the initial point. See also plus distance; taping station. HDBK-850
point A 0[zero]-dimensional geometric primitive. CEN/TC 287
point A position on a reference system determined by a survey. See also amphidromic point; angle point; annex point: antisolar point; astrogravimetric points; cardinal points; check point; control point; datum point; detail points; distant points; fix; image point; initial point; intercardinal point; map point; middle point; nodal point; orientation point; pass point; plus point; principal point; sublunar point; subsatellite point; subsolar point; substellar point; tie point; turning point; wing point; witness point. HDBK-850
point anomaly The value of the gravity anomaly at a specific location as observed or predicted. HDBK-850
point base A manuscript which contains radial centers, picture points, pass points, control points, and tie points from the photographs used in the radial triangulation method. HDBK-850
point feature An object whose location can be described by a single set of coordinates. HDBK-850
point marker A device used for identifying points on diapositives by either marking a small hole in the emulsion or marking a small ring around the detail point itself Also called snap marker. See also point-transfer device. HDBK-850
point of certainty In a simple two-point intersection problem, that point where the two intersecting rays cross and the point is confirmed by the intersection of a third or check ray passing through the same point. HDBK-850
point of compound curvature (PCC) The point on a line survey where a circular curve of one radius is tangent to a circular curve of a different radius, both curves lying on the same side of their common tangent. HDBK-850
point of contact Any level surface along a terrain profile recorder (TPR) flight line that can be flown over both before and after the changing or adjustment of a TPR positional camera magazine, a chart roll, or a recording pen. HDBK-850
point of curvature (PC) The point in a line survey where a tangent ends and a circular curve begins. See also point of tangency. HDBK-850
point of cusp The point of tangency of two curves, the direction of the extension of said curves being of opposite sign; such as the vertex of a Y of a railroad track or a point on the edge of a convex-concave lens. May also be applied to the point of tangency of a straight line and a curve where the direction of extension of the line and curve are of opposite sign. HDBK-850
point of inflection The point at which a reversal of direction of curvature takes place. HDBK-850
point of intersection (Pl) The point where the two tangents of a circular curve meet. Also called vertex of curve. HDBK-850
point of origin See initial point. HDBK-850
point of reverse curvature (PRC) The point of tangency common to two curves, the curves lying on the opposite side of the common tangent. HDBK-850
point of symmetry The point in the focal plane of a camera about which all lens distortions are symmetrical. If the lens were perfectly mounted, the point of symmetry would coincide with the principal point. HDBK-850
point of tangency (PT) The point in a line survey where a circular curve ends and a tangent begins. The point of tangency and point of curve are both points of tangency, their different designations being determined by the direction of progress along the line; the point of curvature is reached first. HDBK-850
point of vertical curve (PVC) The point of change from a line of uniform slope to a vertical curve. HDBK-850
point of vertical intersection (PVI) The point of intersection of two lines, each having different uniform slopes. HDBK-850
point of vertical tangent (PVT) The point of change from a vertical curve to a line of uniform slope. HDBK-850
point position (Doppler) The geocentric or geodetic position of a point determined from satellite tracking data by a Doppler receiver and the satellite(s) ephemerides. HDBK-850
point position data (PPD) The collective result of an analytical triangulation effort that provides evaluated geodetic positions of photoidentifiable ground points or reseau intersections. These positions are the result of an evaluated adjustment of the points to a specific mathematical surface and are expressed in terms of latitude, longitude, elevation, and positional accuracy for each point. HDBK-850
point positioning (surveying) The process of establishing independent survey position. See also short arc; short arc geodetic adjustment; translocation. HDBK-850
Point Positioning Data Base (PPDB) A deployable set of geodetically controlled photographs with associated parameters, indices and application software. Each PPDB contains a series of stereo models covering a specified geographic area and an accompanying reference manual with software disks to be used by the Analytical Photogrammetric Positioning System (APPS). NIMA LOP
point target A target with an area defined by a center point, a major and minor axis, and a target azimuth. Each point target will be described by its Installation or Facility Identification Elements (IIE/FIE) which include BE number, Geographic Coordinates, Target Name, Country Code, and for FIE, Suffix and Category Code. See also target. USIS 2-1.1
point the instrument Turning the survey instrument to where the cross hairs (vertical, horizontal, or both) are accurately aligned with the target. HDBK-850
point-designation grid (JCS) A system of lines having no relation to the actual scale or orientation, drawn on a map, chart, or air (aerial) photograph, dividing it into squares so that points can be more readily located. HDBK-850
pointer (digital) The address of a record or other data groupings contained in another record. HDBK-850
pointing 1. (mensuration) Placing the reticle or index mark of a precision measuring instrument, such as a comparator, within the symmetrical center or center of gravity of a point being measured to determine its position relative to the position of other points in some system of coordinates. 2. (stereocompilation) A general term applied to the movement of the tracing table of a stereoplotting instrument to specific control and/or picture points on the datum during orientation of a stereomodel. 3. See line of sight, definition 2. HDBK-850
pointing accuracy The exactness, in surveying or photogrammetry, with which the line of sight or floating mark can be directed toward a target or image point. HDBK-850
pointing errors Errors which reflect the accuracy with which the floating mark of a stereoplotting system can be located on a sharp model point. These errors generally follow a more or less random distribution but show a systematic trend with progressive working time on the instrument due to eye fatigue and its effect on stereoscopic perception. HDBK-850
pointing line See line of collimation. HDBK-850
point-in-polygon A geographic information system (GIS) routine which assesses whether a point falls within a polygon. HDBK-850
point-matching method (rectification) The technique of utilizing an autofocus rectifier for tilt removal by the manual matching of projected image points to those plotted in their correct horizontal position on a film templet. HDBK-850
Point-to-Point Protocol (PPP) A protocol which encapsulates common network-layer protocols in specialized packets to pass through certain network commands. Multimedia
point-transfer device A stereoscopic instrument used to make corresponding image points on overlapping photographs. Also called transcriber. See also point marker. HDBK-850
polar axis The primary axis of direction in a system of polar or spherical coordinates. HDBK-850
polar bearing In a system of polar or spherical coordinates, the angle formed by the intersection of the reference meridional plane and the meridional plane containing the point. HDBK-850
polar chart 1. A chart of polar areas. 2. A chart on a polar projection. The projections most used for polar charts are the gnomonic, stereographic, azimuthal equidistant, transverse Mercator, and modified Lambert conformal. HDBK-850
polar circle Either the Arctic Circle (north polar circle) or the Antarctic Circle (south polar circle) . HDBK-850
polar coordinates (JCS) 1. Coordinates derived from the distance and angular measurements from a fixed point (pole). 2. In artillery and naval gunfire support, the direction, distance, and vertical correction from the observer/spotter position to the target. HDBK-850
polar diameter The diameter of the Earth between the poles.