Mapping, charting, and geodesy in the DoD standard GPS receivers

The authors present the mapping, charting, and geodesy (MC&G) capabilities of the family of US Department of Defense standard GPS receivers. These include coordinate transformation of input and output position data positioning with respect to local data, and computation of both ellipsoid-referenced and mean-sea-level-referenced altitude. The authors first introduce the coordinate system used internally in the user equipment and show its application to user and satellite position. Second, they show the variety of Earth models available for user coordinates and define their relationships to the internal reference frame. They then explain the different types of map coordinates available through the GPS user equipment and discuss how the transformation algorithm are implemented in software. A description of how the algorithms were tested follows, along with test results