Bernese GPS Software Version 5.0 - Bernese GNSS Software

10.3 Coordinate and Velocity Estimation in Practice
Column (7): Lengths of the principal axes of the 3-dimensional error ellipsoid (in meters).
Column (8): Orientation of the error ellipsoid: zenith distance of the longest axis, azimuth
(counted positive in East) and elevation angle of the second axis (in degrees)
Column (9): Lengths of the principal axis of the 2-dimensional error ellipse in the horizontal
plane (in meters).
Column (10): Orientation of the error ellipse: azimuth of the principal axis counted positive
in East (in meters).
Please note that the internal representation of coordinates and velocities is always cartesian.
Where needed, they are transformed to a geographical system based on the local geodetic
datum defined in the respective a priori coordinate or velocity input file.
The estimated coordinates and velocities can be stored in corresponding result files. They
are flagged according to the applied constraints (see Section 22.8.5). Stations not appearing
in the current session are directly inherited from the a priori input files (but without
flags). Consequently, the resulting files contain all stations from the a priori files, no matter
if actually processed or not. In addition, ADDNEQ2 can write coordinate and velocity results
in SINEX format. Both programs, GPSEST and ADDNEQ2, can store the covariance
information of coordinate parameters.
10.3.2 Static Network Solution
A static network solution is the most common case of coordinate estimation. It is usually
based on double-differenced phase observations with orbit and Earth-orientation information
introduced from an external source, such as the IGS or CODE. In a static solution one set
of coordinates is estimated for the entire session for each station. This is, of course, only
valid if station velocities can be neglected for the processed time interval which is usually
fulfilled for ground mounted tracking stations.
The geodetic datum of the network must be defined based on some reference sites with
well known coordinates, especially for non-global networks. To ensure consistency with the
orbits and Earth orientation parameters, it is recommended to include some nearby stations
from the global IGS network as reference sites. The precise IGS coordinates and velocities
for these stations may then be used for datum definition purposes. A no-net-translation
condition or tight constraints on the single reference stations are well-suited for a final
coordinate solution.
Of course it is advisable to check the performance of the fiducial sites and – if necessary
– to remove problematic stations from the list of reference sites. One possible approach is
demonstrated in theRNX2SNX processing example (sequence PID 511–514, see Section 20.4.2)
utilizing program HELMR1.
10.3.3 Multi-Session Solution
Normal equation systems from subsequent sessions can be combined in a multi-session
solution with ADDNEQ2. All coordinate parameters belonging to the same station (identified
by the station name) are combined to one single set of coordinates. The resulting coordinates
Bernese GPS Software Version 5.0 Page 221