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refprn

Automated reference satellite selection for double difference processing.


The refprn program is used to choose the reference satellites for each of the baselines in the session (as listed in the aazz00.bls file output by the stree program). The program reads in the elv.plt file and the aazz00hd.dat file from the combined, multi-station mergedb run. It uses the elevation angles in elv.plt to judge when gaps appear and when two stations observed the same satellite. It uses the *hd.dat file to determine the order of the stations in the database, and to verify that the database stations match those in the elv.plt file.

The program reads a control file called refprn.inp which has five lines:

25.0 Elevation cutoff angle for choosing the reference SVs.
aazz00.bls Name of the baseline file output by stree
40 Max. gap size (in epochs) allowed for a reference SV
2 18 22 Number of SVs NOT allowed to be reference SVs; list of the PRN numbers for these outlawed ref SVs.
5 Maximum number of dropouts in elv.plt to restart SV in *.out file.
For each baseline the refprn program first creates a list of all satellites and their rise and set times. For each satellite, this list may actually show several start/stop times, depending on how many data gaps the satellite experienced. This list is stored in a rrrruuuu.out file; where rrrr is the name of the hub site and uuuu is the name of the station at the other end of the baseline. The start/stop times in this list reflect the reference SV cutoff angle given in the refprn.inp file.

The final step in the program is to read through the start and stop times in each *.out file and pick the reference satellites by choosing which satellite has the latest stop time (i.e., goes the longest before falling below the elevation cutoff angle). At that epoch where the longest SV does fall below the cutoff angle, the process starts over again (i.e., pick the next SV that goes the longest). This continues until the stop times being judged correspond to the end of the session. The final reference satellites are then output to the rrrruuuu.prn file(s) to be used later when building the pages.inp file.

The input and output files used in refprn are summarized below:

Input Files:
-----------
refprn.inp
aazz00.bls
aazz00hd.dat
elv.plt

Output Files:
------------
refprn.sum
*.out
*.prn


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refprn.html
March 4, 1999
Steve Hilla