Spectra Precision Survey Pro v4.5 Ranger User Manual - Manual (Page 220)

User’s Manual – GPS Mode
210
Projection Mode
Survey Pro has two different modes for calculating local northing and
easting from GPS measurements: Ground – TDS Localization, and
Mapping Plane
.
In Ground - TDS Localization mode, the is no map projection and no
datum to transform geodetic to local coordinates. In this case, a
default map projection is created with the first RTK base setup. Then,
a localization adjustment is solved (Page 247). The localization
adjustment is a 2D similarity transformation that shifts, scales, and
rotates the default map projection’s locations (y,x) into your local
coordinates (N,E). In Ground - TDS Localization mode, when you
measure a distance with an EDM, the distance measured on the
ground is 1:1 with the distance on the local coordinate grid.
In Mapping Plane mode, there is a specified conformal map projection
and geodetic datum to transform geodetic to local coordinates. In this
case, you select the coordinate system from the database file (Page
217). This mapping plane and datum is used to calculate northing
and easting from latitude, longitude and height. If you set your RTK
base on a point with known coordinates, then no additional steps are
required to solve the coordinate system. If you set your RTK base on
an unknown point, then you can solve a localization adjustment to
correct the positions to the proper local coordinates (Page 247). In
Mapping Plane
mode, when you measure a distance with an EDM, the
distance measured on the ground is not usually 1:1 with the distance
on the mapping plane grid. In this case, you must usually use a
combined scale factor (Page 204).
In either horizontal projection mode, you can use one of three
methods to calculate vertical coordinates: You can use a geoid model,
with or without a vertical localization, to transform ellipsoid heights
into local elevations. You can use a vertical localization to transform
ellipsoid heights into local elevations. You can use no vertical
adjustment and use the ellipsoid height differences directly for your
local vertical coordinates.