radial-line plotting
Determination of the location of points by the successive intersection and resection of direction lines radiating from the radial centers of overlapping aerial photographs.

rectification, differential
The process of scanning and reprojecting a photograph onto a horizontal plane in differential elements to remove displacements caused by tilt and relief. The process may be accomplished by any one of a number of instruments developed specifically for the purpose.

rectification, simple
Projection of an aerial photograph (mathematically, graphically, or photographically) from its plane onto a horizontal plane by translation, rotation, and (or) scale change to remove displacement due to tilt of the camera.

relief
Elevations and depressions of the land or sea bottom.

relief shading
Technique for making hypsography on a map appear three dimensional by the use of graded shadow effects. Generally, the features are shaded as though illuminated from the northwest.

remote sensing
Process of detecting and (or) monitoring chemical or physical properties of an area by measuring its reflected and emitted radiation.

representational fraction
Scale of a map or chart expressed as a fraction or ratio that relates unit distance on the map to distance measured in the same unit on the ground.

reproduction
Summation of all processes involved in printing copies from an original drawing. A printed copy of an original drawing made by the processes of reproduction

scale
Relationship existing between a distance on a map, chart, or photograph and the corresponding distance on the Earth.

sea level (water level)
Height of the surface of the sea at any given time.

section
Unit of subdivision of a township; normally a quadrangle 1 mile square with boundaries conforming to meridians and parallels within established limits, and containing 640 acres as nearly as practicable.

sensor
Technical means, usually electronic, to extend man's natural senses by detecting emitted or reflected energy. The energy may be nuclear, electromagnetic (including the visible and invisible portions of the spectrum), chemical, biological, thermal, or mechanical

shoreline
Intersection of the land with the water surface.

slope map
See: map, slope

soil map
See: map, soil

spheroid
Mathematical figure closely approaching the geoid in form and size and used as a surface of reference for geodetic surveys. A reference spheroid or ellipsoid is a spheroid determined by revolving an ellipse about its shorter (polar) axis and used as a base for geodetic surveys of a large section of the Earth (such as the Clarke spheroid of 1866 which is used for geodetic surveys in the United States).

spot elevation
Point on a map or chart whose height above a specified datum is noted, usually by a dot or a small sawbuck and elevation value. Elevations are shown, on a selective basis, for road forks and intersections, grade crossings summit of hills, mountain

stadia
Technique of distance measurement wherein the observer reads the intercept subtended on a graduated rod between two marks on the reticle of the telescope.

standard-accuracy adjustment
See: adjustment, standard-accuracy

state plane coordinate system
Coordinate systems established by the U.S. Coast and Geodetic Survey (now the National Ocean Survey), usually one for each state, for use in defining positions of points in terms of plane rectangular (x,y) coordinates.

stereocompilation
Production of a map or chart manuscript from aerial photographs and geodetic control data by means of photogrammetric instruments.

stereoplotter
Instrument for plotting a map by observation of stereomodels formed by pairs of photographs.

stereoscopic
Pertaining to the use of binocular vision for observation of a pair of overlapping photographs or other perspective views, giving impression of depth.

storm evacuation map
See: map, storm evacuation

subsidence
Decrease in the elevation of land surface due to tectonic, seismic, or artificial forces, without removal of surface material.

survey
Orderly process of determining data relating to any physical or chemical characteristics of the Earth. The associated data obtained in a survey. An organization engaged in making a survey.

tacheometer (tachymeter)
Surveying instrument designed for use in the rapid determination of distance, direction, and difference of elevation from a single observation, using a short base which may be an intergraph part of the instrument.

thematic map
See: map, thematic

theodolite
Precision surveying instrument for measuring horizontal and vertical angles.

tide
Periodic rise and fall of the water resulting from gravitational interactions between the Sun, Moon, and Earth. The vertical component of the particulate motion of a tidal wave. Although the accompanying horizontal movement of the water is part of the same phenomenon, it is preferable to designate this motion as tidal current.

topographic map
See: map, topographic

topography
Configuration (relief) of the land surface; the graphic delineation or portrayal of that configuration in map form, as by contour lines; in oceanography the term is applied to a surface such as the sea bottom or surface of given characteristics within the water mass.

township
Unit of survey of the public lands of the United States, normally a quadrangle approximately 6 miles on a side with boundaries conforming to meridians and parallels within established limits, containing 36 sections. Also, in minor governmental subdivision.

transit
Precision surveying instrument; a theodolite in which the telescope can be reversed in direction by rotation about its horizontal axis.

traverse
Sequence of lengths and directions of lines connecting a series of stations, obtained from field measurements, and used in determining positions of the stations.

triangulation
Method of extending horizontal position on the surface of the Earth by measuring the angles of triangles and the included sides of selected triangles.

trilateration
Method of surveying wherein the lengths of the triangle sides are measured, usually by electronic methods, and the angles are computed from the measured lengths. Compare with triangulation.

Universal Transverse Mercator (UTM) grid
Military grid system based on the transverse Mercator projection, applied to maps of the Earth's surface extending from the Equator to 84 Degrees north and 80 degrees south latitudes

upland
Highland; ground elevation above the lowlands along rivers or between hills.

zenith telescope
Instrument for observing starts near the zenith (a point on the celestial sphere directly above the observer's position). ground below the water table where all the pores in rock, sediment, and soil are filled with water