Terms starting with S

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. 

SHORELINE

Intersection of the land with the water surface.

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. 

STATE PLANE

A standard set of coordinate systems used in the US for mapping.

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

Imagery with three-dimensional characteristics that creates the illusion of depth.

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

SUBSIDENCE

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

SUN-SYNCHRONOUS ORBIT

A near-polar orbit where the satellite always crosses the equator at the same local solar time.

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.