Bernese GPS Software Version 5.0 - Bernese GNSS Software

10. Station Coordinates and Velocities
Station coordinates and velocities are probably the most sought-after result of GNSS analyses.
But moreover, good coordinates are a prerequisite for the accurate determination of
most other parameters. Thus, the estimation of precise station coordinates will eventually
become an issue in virtually all GNSS analyses.
GNSS is basically a differential technique, i.e., it only gives access to precise relative geometry
information and not to absolute positions. This is rooted in the fact that the measurements
are related to ranges only through unknown clock corrections and phase ambiguity
parameters. As a matter of fact, the geodetic datum of GNSS-based site coordinates obtained
in a network solution has to be defined by introducing external information. Reference
frame issues and geodetic datum definition are intimately connected with coordinate
estimation and are addressed in this chapter.
When estimating coordinates with the Bernese GPS Software two major processing modes
can be distinguished, namely the precise point positioning (PPP) and a differential (relative)
mode. PPP relies on precise orbit and clock information for deriving precise site coordinates
and receiver clock corrections independently for each analyzed station and is based on
undifferenced code and/or phase observations (Section 10.5). The differential mode promises
highest precision for the relative geometry between the sites processed together in a network
solution.
The Bernese GPS Software allows to estimate site coordinates in a network analysis based
on undifferenced or double-differenced observations. Full profit from the integer nature of
the phase ambiguities can only be taken in the second case, which is thus the first choice
for obtaining highest quality results (see Chapter 8).
Apart from static coordinates the Bernese GPS Software, Version 5.0 , offers the possibility
to estimate kinematic site coordinates (Section 10.4). Linear station velocities may be
derived from a multi-session solution using program ADDNEQ2 which operates on normal
equation level (Section 10.3.3). Several additional programs are available for comparing or
manipulating coordinate files (Section 10.6).
10.1 Site Displacement Modeling
To ensure a high accuracy of coordinates and other parameters estimated with the Bernese
GPS Software, a careful modeling of site displacements is mandatory. The most important
effects and adopted models are described in the following.
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