Bernese GPS Software Version 5.0 - Bernese GNSS Software

9. Combination of Solutions
9.4 The Program ADDNEQ2
9.4.1 Flow Chart of the Program
Figure 9.5 shows the flowchart with the important blocks of program ADDNEQ2. For each
input normal equation file first stations are renamed according to the station information
file and parameters without observations are eliminated, i.e., columns and rows with a
zero diagonal element on the normal equation matrix are removed. In a next step the input
normal equation is rescaled according to variance rescaling factors defined in the file specified
in option “Variance rescaling factors” in panel “ADDNEQ2 1: Input Files” (see Section 9.3.2). In the
same file a priori Helmert transformation parameters may be specified, too (Section 9.3.3).
The next step is the transformation of the a priori parameters according to the equations
in Section 9.3.4 to values specified by external files. A priori values are always transformed
and as a general rule input files have to be specified in panel “ADDNEQ2 1: Input Files”
for all parameters contained in the normal equations. This is particularly true for station
coordinates or Earth rotation parameters. Troposphere parameters are a special case for
which the input troposphere file is used to fix parameters (see Section 9.4.3). If a velocity
input file is specified the station coordinate parameters are transformed to a priori values
for the middle epoch of the input normal equation (see Section 10.3.4).
The spacing of the piece-wise linear description of time-dependent parameters is adapted
as a next step according to the user input (see Section 9.4.5). Then parameters are deleted
on user request, constraints are added to parameters scheduled for pre-elimination and the
pre-elimination (”before stacking”) is performed. For details on the available pre-elimination
options in ADDNEQ2 see Section 9.4.4.
The stacking of parameters from the input normal equation with those from the previous
normal equations concludes the loop over the input normal equations. Orbit parameters
need a special transformation before they can combined to to a long arc over several normal
equations (see Section 15.3.2).
The next step prepares the saving of the resulting normal equation to file. This involves
the pre-elimination of parameters (”after stacking”) after applying the user-specified constraints,
the sorting of the parameters in the normal equation, and the saving of the binary
normal equation file.
Then the solution is computed after constraining the parameters that were not preeliminated.
The results are written to the program output and the parameter specific output
files are prepared.
If option “Compute and compare individual solutions” in panel “ADDNEQ2 3.1: Options 1” is set to
YES or HELMERT each input normal equation is read a second time, an individual solution is
computed with identical options as for the combined solution and compared to the combined
solution. The result from this step are station coordinate residuals for each station from each
input normal equation. Depending on the number and size of the input normal equations
this step may be time consuming, however. For details we refer to Section 10.3.3.
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