GED User's Guide

Notes:

1. "Cartesian (Orthonormal) Geodetic" is used here to denote a global mapping of data referenced by Longitude and Latitude to an Cartesian (x = latitude, y = longitude), orthonormal (meaning independent, perpendicular axes) linear (equal intervals) coordinate system. This is also referred to as a "Platte Carree" or simply "Latitude /Longitude" projection. Note: Some references point out that this is not a "projection" in the traditional sense, because it cannot be produced by physical projection from a sphere onto a euclidean plane, but it is nevertheless a mathematical mapping of geodetic coordinates onto a euclidean plane. The term "unprojected" is sometimes used to indicate that there is no coordinate conversion, however this does not describe the mapping. Properties: Distances are true (for a spherical geoid) along all meridians and the equator. Scale, area, direction, and angular distance vary with latitude. The value of this projection is its simplicity and use as a basis for collecting data and for producing other projections. [Please use Browser's back button to return to previous text.]
2. "Albers" refers to the Albers Equal Area Conic projection. Properties: All areas on the map are proportional to the same areas on the Earth. Directions are reasonably accurate in limited regions. Distances are true on both standard parallels. Maximum scale error is 1 1/4% (Conterminous United States). Scale is true only along standard parallels. Map is not conformal, perspective, or equidistant. (ref: USGS Map Projections) [Please use Browser's back button to return to previous text.]
3. "Metadata" refers generally to "data about data." For the purposes of the GED, this definition is too broad and must be distinguished from "Documentation" (see below). As a working definition, "metadata" is taken to mean field-coded (e.g., system-level) data used by software to properly interpret, reference, or manipulate data files. [Please use Browser's back button to return to previous text.]
4. "Documentation" refers generally to "information about datasets and data products." In modern usage, the definition of this term overlaps with the definition of "metadata" (see above). As a working definition for the GED, "documentation" is taken to mean analog or digital text documents read primarily by people to understand datasets and data products. [Please use Browser's back button to return to previous text.]