Which reference ellipsoid surface do we use in the Air Force?

• A. Universal Transverse Mercator (UTM)
• B. World Geodetic System 1984 (WGS84)
• C. Geographic Coordinate System (GCS)
• D. North American Datum 1983 (NAD83)

Answer: (B)

The essential idea is the global reference surface used for all position calculations in military navigation. The Air Force relies on a worldwide, fixed geodetic frame, and that frame is defined by the World Geodetic System 1984. GPS coordinates are broadcast and interpreted in this system, providing a single, consistent reference across the globe for navigation, targeting, and mapping. Nad83 is a regional datum centered on North America and, while similar, is not the standard global surface used for DoD operations. UTM is a projection method, not the underlying ellipsoid, and Geographic Coordinate System describes a type of framework rather than the specific surface. So the surface used for reference is WGS84.