Spectra Precision Survey Pro v4.5 Recon and Nomad Reference Manual - Manual (Page 183)

Survey Menu – GPS Module
R-175
Choose Projection Mode
The Start GPS Survey Choose Projection Mode screen is used to
select a horizontal projection mode. This screen shows when you
have not yet solved a coordinate system for this job.
You can choose one of two projection modes, depending on the
requirements for your survey.
Use Ground – TDS Localization >: sets the horizontal
projection mode to Ground – TDS Localization, and opens
the Choose Base Setup screen. Use this mode when you
want to do a ground level survey, when there is no
projection and no datum to relate your local coordinate
system to any geodetic coordinate system.
Select a Mapping Plane Zone >: sets the horizontal
projection mode to Mapping Plane, and opens the Select
Coordinate System screen (Page R-204). Use this mode
when you want to use a conformal map projection
selected from the coordinate system database file.