Bernese GPS Software Version 5.0 - Bernese GNSS Software

7.5 Parameterization
In case of non-final double-difference solutions such as intermediate solutions for residual
screening, the correlation strategy BASELINE may be applied in order to speed-up processing.
This strategy should always be used for ambiguity resolution. With this strategy baselines
are processed sequentially (and not in parallel as in the case of correct correlations) and
only correlations within each baseline are considered. Especially when pre-eliminating ambiguities
this “baseline mode” is very efficient, because memory for ambiguity parameters
of only one baseline is required. After one baseline has been processed the ambiguities are
pre-eliminated from the normal equation system and the ambiguity parameters of the next
baseline are loaded in their place.
If zero-difference observations are processed no mathematical correlations between observations
exist. Nevertheless, the correlation strategy CORRECT has to be used as soon as
satellite clocks are estimated or code and phase observations are processed together because
in both cases the observation files from the different stations resp. observation types
have to be processed simultaneously. This is important because epoch-specific parameters
such as satellite clock corrections (which are common to the observations from different
stations) are pre-eliminated epoch-wise.
Temporal correlations that may also exist between observations are in no case considered
within the Bernese GPS Software.
7.5 Parameterization
7.5.1 Types of Parameterization
The list of adjustable parameters implemented in program GPSEST is given in Table 1.1.
The following chapters give details on the estimation of the different parameters. The parameterization
as a function of time may have three different forms:
(1) A parameter may be constant for the entire session. This is, e.g., the case for station
coordinates in GPSEST (not necessarily in ADDNEQ2), antenna offsets or patterns,
orbital parameters, or code bias parameters.
(2) A parameter may be represented as a piece-wise linear function, a polygon in time.
Troposphere parameters and ionosphere parameters are parameterized in this way.
Note that this parameterization causes no discontinuities between parameter sets as
it was the case, e.g., for the parameterization of troposphere zenith path delay parameters
in the Bernese GPS Software Version 4.2 or earlier.
Earth orientation parameters are represented in GPSEST by offsets and drifts. A
continuity condition may be applied between adjacent parameter sets. For program
ADDNEQ2 the parameters are transformed to a piece-wise linear representation.
(3) Parameters may be valid for a single observation epoch only. Clock offsets or kinematic
coordinates are the examples for this type of parameterization.
Phase ambiguities are somewhat special as they are represented as constant parameters
but valid only until the next ambiguity parameter for the respective combination of station
and and satellite becomes valid. Some of the constant parameters, e.g., satellite antenna
offsets, may be set up several times per session and thus allow for a piece-wise constant
(non-continuous) modeling.
Bernese GPS Software Version 5.0 Page 147