It is true that GPS uses internally all metric for its operations. The end result is a position in an Earth centered Earth fixed (ECEF) cartesian coordinate system in meters. The use of this position depends on the use that is expected by the "receiver". For military applications, latitude and longitude in WGS 84 may be the dominate one but UTM is also needed. For many other applications, the result may be one of a few hundred geodetic datums. Makers of simpler GPS receivers have functions to produce output in any of these datums and other measurement systems depending on the market place. In the US, the customary system is supported but metric is readily available by screen selection. The flexibilty of "GPS" to support many different geodetic datums and measurement systems is due to the foresight of the developers who created a very general system capable of being useful in many different environment.
In the US, for example, many charts or maps are still being used in NAD27 so GPS users need the ability to produce output in that datum. It will probably be many years if ever that these charts will be updated to WGS84(G1150) or what ever reference frame is in use. m f moon
