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Figure 3-6:
Ephemeris selection
3.5.5.1 Default Ephemeris
The default RINEX data for GPS and GLONASS is based on the CDDIS GNSS archive ,
using the brdc files. The non-redundant brdc file merges the individual site navigation files
into one, and thus can be used instead of the many individual navigation files.
This data is complemented by GLONASS almanac data downloaded from
ftp://www.glonass-iac.ru/MCC/ALMANAC/ , covering the same period (file names are
prefixed by receiver types, e.g. MCCT_ , MCCJ_, GG-24, or TOPCOM_).
The default navigation data begins Jan 8, 2012 and runs for 33 consecutive days.
For Galileo, BeiDou, and IRNSS, the GSG unit comes shipped with its own ephemeris data
set.
When the ephemeris setting is set to Default , the GSG unit builds all scenarios, any start
date, using the default data. If there is an exact match for the scenario Start time and pre-
loaded navigation files, that navigation data will be used. If an exact date match is not
found, then the GSG unit will use the first preloaded navigation data with the same day of
the week as the scenario’s start time. Further simulation days will use consecutive in date
navigation data.
In general, the start time of the scenario always supersedes the time stamps in the nav-
igation data files. If file date and scenario start time do not match, then the loaded data is
transformed accordingly to match the scenario’s start time. If the scenario defines a GPS
almanac files only, the YUMA files will define the almanac and the ephemeris will be
derived from the default RINEX data.
3.5.5.2 Download Ephemeris
The user can let the unit automatically download navigation data from official websites.
The navigation data,
brdc
files and GLONASS almanac files are retrieved from the same
sites as mentioned under "Default Ephemeris" above .
For this feature to work, the following requirements must be met:
48 User Manual GSG-5/6 Series Rev. 27
3.5 "Select" Menu