Bernese GPS Software Version 5.0 - Bernese GNSS Software

10. Station Coordinates and Velocities
Figure 10.8: Present-day major tectonic plate boundaries.
one of the selected files, the corresponding flags are compared and the coordinate/velocity
set with the flag of highest priority will be stored in the resulting file. Note that flags may
have up to 5 characters for coordinates and up to 4 characters for velocities but only the
first character is of importance for comparison.
The defined flags are listed in Section 22.8.5 with increasing default priority. The priority
sequence of the flags may be adapted easily to particular needs in panel “CRDMERGE 2:
Options”. A blank flag always has the lowest priority. One-character flags may be translated
to longer identifiers during the merging process (e.g., N to NET). Changing the geodetic
datum and reference epoch only affects the strings written to the new file, coordinates are
not transformed.
10.6.6 Computing Velocities from a Model
Program NUVELO (”Menu>Service>Coordinate tools>Compute NUVEL-velocities”) computes station velocities
based either on the NNR-NUVEL-1 [Argus and Gordon, 1991] or on the NNR-
NUVEL-1A [DeMets et al., 1994] tectonic plate motion model (the boundaries of the major
tectonic plates are shown in Figure 10.8). If a site is not available in the list of ITRF coordinates
and velocities the NUVEL velocities serve as good approximation for station velocities
to propagate the station coordinates from the reference epoch of the reference frame to the
epoch of the observation.
A subset or all stations contained in an input coordinate file may be selected. The program
computes the model velocities based on a plate definition file (description in Section 22.8.8).
If a station name is not listed in the plate definition file, a zero velocity vector results.
The obtained velocities may be merged into an a priori velocity file. Velocities for stations
already contained in this file are overwritten. Use program CRDMERGE for more flexibility
in merging of velocity files. The stations for which velocities were computed are marked
with the flag V.
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