Spectra Precision Survey Pro v4.6 Ranger User Manual - Manual (Page 269)

GPS Module
259
Solve Localization
When you start a GPS survey from an autonomous base position, you
need to solve a localization to adjust GPS measurements into local
coordinates. This is the case for both horizontal projection modes.
Using Ground - TDS Localization, you need to solve a localization to
relate your arbitrary GPS start point into your non-geodetic local
system. Using a Mapping Plane, you need to solve a localization to
shift the autonomous GPS start point into accurate geodetic
coordinates.
In either horizontal mode, the procedure is the same. Starting from
an autonomous GPS base setup, you measure GPS positions on
control points with know local plane (N,E) coordinates. The
parameters for a 2D similarity transformation are calculated with a
least squares solution using the control points. These parameters are
added to the zone record (the default Ground - TDS Localization mode
zone or the selected Mapping Plane mode zone) to create a zone based
site record.
Vertical localization, with or without a geoid model, uses the same
field procedure. Starting from an autonomous GPS base setup, you
measure GPS positions on control points with know local elevations.
The vertical adjustment parameters are calculated from the control
points. The vertical adjustment will be either a shift to correct geoid
elevations to local elevations, or an inclined plane to correct for
vertical shift and tilts.
Note: If you are starting a new job from an autonomous GPS base
setup using one point setup, you do not need to solve a localization
adjustment. The default map projection will be scaled to ground, and
oriented with grid north equal to geodetic north at your first base
station.