Spectra Precision Survey Pro v3.80 Recon GPS User Manual - Manual (Page 51)

RTK Data Collection
47
Ground - TDS Localization Explained:
When the horizontal projection mode is Ground - TDS Localization , a
default map projection is automatically set up to produce ground
coordinates at the base station height. The TDS Localization map
projection is an oblique stereographic map projection with the
following parameters:
o Origin is at the initial base station location
o False northing and false easting of 100000.0 m
o Scale at the origin of the stereographic map projection zone is
calculated to produce ground scale distances at the height of
the first GPS setup. This projection scale factor is simply the
inverse of the ellipsoid scale factor described earlier (see page
12).
Origin Scale (k
map
) = (R+h)/ R
2
1
2 2 ) sin 1 (
φ
e
a
R
−
=
Localization Setup Groups
When you set up different base stations with autonomous positions
from a GET, each position is only accurate to +- 30m (+- 10 m with
Selective Availability (SA) turned off). Geodetic coordinates
measured from your first autonomous base will not be accurately
connected to geodetic coordinates from a different autonomous base.
Although the localization parameters will accurately transform both
sets of data to the local coordinate system, it is not possible to
compare the geodetic coordinates from the different sets of data.
Survey Pro solves this problem by assigning a set up group each time
a new autonomous base is set. A set up group is a unique flag
attached to each point record generated by GPS. Setup groups are
assigned as follows:
•
When you set a new base point with an autonomous GET, Survey
Pro creates a new set up group for this point.