Bernese GPS Software Version 5.0 - Bernese GNSS Software

5. Preparation of Earth Orientation, GNSS Orbit, and Satellite Clock Information
5.5 Preparation of Satellite Clock Corrections
Satellite clock corrections are necessary for the synchronization of the receiver clocks. The
synchronization is performed in the data preprocessing step using program CODSPP, see
Section 6.3. The satellite clock corrections with respect to GPS time may be extracted from
three sources, namely from broadcast messages, from IGS precise orbit files, or from IGS
clock RINEX files (see Chapter 4).
You will in general produce a satellite clock file in PRETAB when converting precise orbit
information into tabular format (see Section 5.4.1). You will fit the satellite clock information
from the precise files within intervals of several hours (12 hours is recommended in panel
“PRETAB 3: Options for Clocks”) by low degree polynomials (the recommended degree is q = 2)
and thus create a satellite clock file which may be used to compute satellite clock corrections
for each observation epoch. This way of handling the clocks in the precise files is the normal
case.
You also have the possibility to extract the unaltered satellite clock corrections from the
precise orbit files (usually given at 15 minute intervals) by asking for a polynomial degree
and an interval length of “zero”. This way, for observations made exactly at the time of
the tabular epochs in the precise orbit file, you may access the very precise IGS satellite
clock information (e.g., in case that Selective Availability SA is enabled). Program CODSPP
may take profit out of this special case for handling precise clock information, if you are
asking for the correct option in this program. The option may also be used to perform a
precise point positioning with program GPSEST (see Section 10.5). In general this option is,
however, rather harmful due to the significant data reduction (one epoch every 15 minutes
instead of, e.g., every 30 seconds). Therefore, use this special option with care!
Program SATCLK (”Menu>Orbits/EOP>Broadcast orbits>Extract satellite clocks”) extracts satellite clock
information from broadcast files generated by program RXNBV3 and writes it into a satellite
clock file in the Bernese format (see Section 22.7.10). You may also generate a satellite
clock file for use in CODSPP or GPSEST from Clock RINEX files using program CCRNXC
(see Section 14.3). Clock RINEX files available from the IGS contain clock values for every
5 minutes instead of every 15 minutes as for the IGS precise orbit files. From CODE, precise
clock information at a rate of 30 seconds is available since March 2004 (see Section 4.12.1).
5.6 Concatenation of Orbit Information and Orbit Comparison
5.6.1 Concatenation of Precise Orbit Information
Let us briefly discuss the program CCPREORB (”Menu>Orbits/EOP>Cut/concatenate precise orbit
files”). This program allows to merge two orbit files in SP3 format: all satellites found in
the first file are written into the new orbit file. If the second file contains further satellites
(e.g., GLONASS satellites), they are added to the new orbit file. In this way it is possible to
use, e.g., the GPS orbit information from one SP3 file and the GLONASS orbit information
from another SP3 file or to merge precise GPS orbits in the SP3 format with GLONASS
broadcast orbits in the SP3 format.
Several options are available to control the merging of two precise files. Priority of individual
satellites from the two files may be adapted based on the prediction flags in SP3c
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