Spectra Precision FAST Survey Reference Manual - Manual (Page 89)

p87
If it is a very accurate latitude and longitude, you will get the best results. Pressing OK leads to the option of store
the base position as a reference file, similar to Read from GPS.
 Enter Grid System Coordinates
: Requires you to enter the grid system northing and easting for the point that the
base is occupying. This applies to any projection that you have configured, including U.S. state plane, worldwide
UTM or any individual country or user-defined grid system. This is useful if you are setting up over a monument
whose coordinates you know. An accurate base position, either by entry of Lat/Long or Grid System Coordinates,
will enable immediate data collection without rover-based localization, but also will improve rover-based
localization.
The Coordinate method is similar to the Lat/Lon method, since Lat/Longs convert to Grid Coordinates based on the
current coordinate system set in Job Settings, GPS option. The Grid Coordinates will convert back to the Lat/Long
coordinates needed by FAST Survey to configure the base.