Bernese GPS Software Version 5.0 - Bernese GNSS Software

5.4 Preparation of Precise Orbit Information
a pole file (see “Pole file” in panel “BRDTAB 1: Filenames” and Section 22.7.8) with information
concerning the Earth orientation parameters (and in program ORBGEN, below). You
will probably use information which originally comes from the IERS Bulletin A or B. The
POLE-file has to be in the Bernese format, see Section 5.2. The file BULLET A.ERP may be
retrieved by anonymous ftp from http://www.aiub.unibe.ch/download/BSWUSER50/ORB/
(see Section 4.12.1).
Starting from tabular orbit files the program ORBGEN is used to generate standard orbits.
The procedure is described in Section 5.4.
5.3.3 Checking GNSS Broadcast Messages
The program RXNPRE (”Menu>RINEX>Import RINEX to Bernese format>Navigation files to SP3”) checks
the broadcast messages of GPS and GLONASS satellites, eliminating bad messages
and identifying satellite shifts (maneuvers). Alternatively the program BRDTST (”Menu
>Orbits/EOP>Broadcast orbits>Check broadcast orbits”) may be used to check GPS broadcast messages
in Bernese format.
The programs RXNPRE and BRDTST are able to process more than one broadcast file in the
same program run. For each file and each satellite the broadcast messages and the satellite
clock parameters are checked for two different types of errors and one type of events:
(1) If a message or a clock parameter is obviously wrong (e.g., an inclination of 2 degrees)
the status in the display is set to BAD A (bad semi major axis), BAD E (bad
eccentricity), BAD I (bad inclination), etc.
(2) If a message or a clock parameter has a reasonable value, but the difference to the
corresponding element of the previous message is unreasonably big, the status is set
to BAD DA, BAD DE, etc.
(3) If the orbital elements in the messages show big jumps between two subsequent epochs
but are consistent before and after this jump, it is assumed that the satellite was
repositioned or maneuvered. If such a jump is detected, the satellite number, the
precise epoch, etc., will be listed at the end of the program run and all the messages
of this satellite after the jump will obtain a new satellite number which is equal to
the old satellite increased by 50 (PRN’= PRN+50). This ’artificial’ satellite will then
be treated like a normal satellite (see also end of Section 5.4.2).
The thresholds for identifying bad messages are hard-wired in subroutines CHKBR1 and
CHKBR2. Figure 5.3 shows an extraction of the output produced by program BRDTST for
a particular program run. A similar output is written by program RXNPRE.
5.4 Preparation of Precise Orbit Information
Precise GNSS orbits are a prerequisite for all precise applications of the GNSS. Today
highest precision GPS and GLONASS orbits are available through the IGS resp. its Analysis
Centers 4 . For more information on available orbits and the estimated prediction of the
4 The GLONASS orbits are currently combined separately from the GPS orbits within the IGS. Fully
consistent GPS/GLONASS orbits may be obtained from CODE’s precise orbit files.
Bernese GPS Software Version 5.0 Page 89