Bernese GPS Software Version 5.0 - Bernese GNSS Software

5. Preparation of Earth Orientation, GNSS Orbit, and Satellite Clock Information
The orbit programs may be found under the menu item ”Menu>Orbits/EOP”. The orbit part
contains programs for checking and converting broadcast ephemerides and extracting broadcast
clocks, to convert precise orbit information into the Bernese standard orbit format, and
to generate precise orbit files starting from standard orbit format. Additional tools for extracting
and converting Earth orientation parameters, for the preparation of satellite clock
information necessary for receiver clock synchronization, for extracting information from
the orbit integration program, and to compare precise orbit files or standard orbit files are
available.
The Bernese GPS Software knows several orbit formats (see Table 5.1). The international
format for exchanging precise orbit information within the IGS is the SP3c format. Reading
routines recognize the new format versions as well as older versions of the precise file format
(SP3, SP2 or SP1). The precise orbit files (default extension PRE 1 ) give geocentric Cartesian
coordinates (in kilometers) of the satellites in an Earth-fixed frame together with satellite
clock information for a table with equidistant epochs (usually 15 minutes). For a description
of the file format see ftp://ftp.igs.org/pub/data/format/sp3.txt or [Remondi, 1989].
See also Sections 4.4 and 4.12.
The Bernese-internal tabular orbit files are ASCII files (default extension TAB) containing
Cartesian satellite coordinates (in kilometers) in the inertial frame, tabulated at regularly
spaced epochs. The so-called standard orbit files (default extension STD) are binary files
specifying the position of the satellites in the form of a polynomial representation and
are the result of a numerical integration of the equations of motion. All programs of the
Bernese GPS Software that require GNSS orbit information read standard orbit files. Earth
orientation parameters are required for all programs accessing standard orbit files in order
to perform the transformations between the Earth-fixed and the inertial frame. In addition
to the file formats listed in Table 5.1 broadcast information in RINEX and Bernese format
can be processed in the Bernese GPS Software.
This chapter first describes how to import and prepare Earth orientation parameters (next
section). Section 5.3 presents the programs available for preparing broadcast information.
Section 5.4 shows how to interpolate precise orbit files and to prepare the orbit information
in the standard orbit format. This is the standard application of the orbit programs in the
Bernese GPS Software. Section 5.5 describes how to extract satellite clock information from
broadcast or precise orbit files, an information which is important to synchronize the receiver
clocks in the data preprocessing step. In the last section the orbit comparison programs are
described. Information on how to estimate orbit and Earth orientation parameters are given
in Chapter 15. For more information on estimating satellite clocks we refer to Chapter 14.
1 In most databases these files have extensions EPH or SP3.
Table 5.1: Important orbit formats used in the Bernese GPS Software.
File Type Format Content, Reference System
PRE Precise Orbit File, SP3 International, ASCII Tabular positions and clocks,
Earth-fixed, geocentric, every 15 min
TAB Tabular Orbit File Bernese, ASCII Tabular positions,
inertial, geocentric, every 15 min
STD Standard Orbit File Bernese, binary Polynomial representation,
result of numerical integration, inertial,
geocentric
Page 84 AIUB