Bernese GPS Software Version 5.0 - Bernese GNSS Software

10. Station Coordinates and Velocities
While the first option has to be used for large regional and global sets of coordinates,
the second option is particularly useful for the interpretation of transformation parameters
between small regional and local networks. Note that the residuals in the program output
are given in the north, east, and up components in both cases.
The program allows to estimate only a subset of the seven Helmert transformation parameters
by selecting the options in panel “HELMR1 2: Options for Helmert Transformation”
accordingly.
The user may select the stations that shall be used to compute the transformation parameters
manually or automatically. Stations may either be marked or excluded. Marked
stations are not used for computing the transformation parameters but the program provides
residuals in the output file (marked with a flag M) while excluded stations are not
considered at all. In manual mode the user may mark and exclude stations manually from
a list containing all stations with a flag in both files. In automatic mode a station selection
file may be specified in “File with list of stations” in panel “HELMR1 1: Input/Output Files”. Only
stations listed in this file are considered for computing the transformation parameters while
the other stations are marked or excluded according to user selection.
The program allows it to iteratively remove stations with residuals exceeding thresholds
that may be specified in panel “HELMR1 3: Outlier Rejection”. A station selection output
file may be written containing only those stations that passed the thresholds. The other
stations are marked with an asterisk in the output and their names and residuals may be
written to a special output file. The option is useful, e.g., for an automatic reference site
verification (see Section 10.2.3). Compare the coordinates of the reference sites obtained
from a minimum constraint solution with the reference coordinates (e.g., IGS05) using
an input station selection file listing only the reference station names. The output station
selection file then contains the same station names reduced by the badly performing stations.
This selection file containing only the verified reference stations can then be used for datum
definition of the final solution in an additional ADDNEQ2 run. In the RNX2SNX processing
example described in Section 20.4.2 this procedure is demonstrated in the sequence of
PID 511–514.
Program HELMR1 may output a coordinate file that contains the station coordinates from
the second input file transformed to the system of the first input file using the estimated
transformation parameters. The same transformation may also be performed with program
COOSYS (”Menu>Service>Coordinate tools>Transform coordinates”) that allows to apply an arbitrary
Helmert transformation according to Eqn. (10.1) to an input coordinate file (assuming small
rotation angles).
10.6.3 Coordinate Transformation to ETRS89
Program ETRS89 (”Menu>Service>Coordinate tools>Transform to ETRS89”) allows to transform site
coordinates from ITRFxx to the European reference frame ETRS89. The epoch for the
time dependent transformation is taken from the corresponding header line in the coordinate
file. Use program COOVEL (see Section 10.6.7) to propagate the coordinates to a specific
epoch before applying ETRS89. The output coordinate file does no longer refer to ITRF.
Be careful not to use the file as reference frame in further analyses. Check the on-line help
for the specific transformation parameters.
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