Which datum is used by the GPS constellation to provide x, y, and z coordinates?

Which datum is used by the GPS constellation to provide x, y, and z coordinates?

• A. NAD27 UTM
• B. WGS84 UTM
• C. NAD83 UTM
• D. WGS84 Geographic

Answer: (B)

GPS coordinates are defined in a global geocentric reference frame tied to the WGS84 ellipsoid, where x, y, and z represent positions in a fixed 3D space relative to the Earth's center. To express those positions as planar coordinates in meters, a projection like UTM is often used, but the underlying datum remains WGS84. The other options rely on different datums (NAD27 or NAD83) or would give latitude, longitude, and height rather than three Cartesian coordinates. Since the question asks for x, y, and z coordinates, the datum that best fits the GPS framework among the choices is the WGS84 with its practical projection form, which is why the option combining WGS84 with a UTM projection is the most appropriate.

GPS coordinates are defined in a global geocentric reference frame tied to the WGS84 ellipsoid, where x, y, and z represent positions in a fixed 3D space relative to the Earth's center. To express those positions as planar coordinates in meters, a projection like UTM is often used, but the underlying datum remains WGS84. The other options rely on different datums (NAD27 or NAD83) or would give latitude, longitude, and height rather than three Cartesian coordinates. Since the question asks for x, y, and z coordinates, the datum that best fits the GPS framework among the choices is the WGS84 with its practical projection form, which is why the option combining WGS84 with a UTM projection is the most appropriate.