SkyWatch EarthCache uses the World Geodetic System 1984 (WGS 84) format for expressing coordinates.
WGS 84 is an Earth-centered, Earth-fixed terrestrial reference system and geodetic datum. WGS 84 is based on a consistent set of constants and model parameters that describe the Earth's size, shape, and gravity and geomagnetic fields. WGS 84 is the standard U.S. Department of Defense definition of a global reference system for geospatial information and is the reference system for the Global Positioning System (GPS). The error of WGS84 is believed to be less than 2 centimeters to the center mass.
A polygon, or area of interest, is an area defined by a minimum of four pairs of coordinates. The first and last pair of coordinates must be identical to close the polygon. In each pair of coordinates:
- Longitude is a decimal number between -180.0 and 180.0, measured at the center of the pixel. Positive (+) value indicates East longitude; negative (-) value indicates West longitude. Units are in degrees.
- Latitude is a decimal number between -90.0 and 90.0, measured at the center of the pixel. Positive (+) value indicates North latitude; negative (-) value indicates South latitude. Units are in degrees.
To find the exact location of a point on a map using WGS 84 format, you can head over here.