Orolia GSG-5 Series, User Manual With Scpi Manual, Page: 101 / 392

Considerations
If a scenario needs SBAS messages that cannot be downloaded from these FTP sites, the
scenario continues, but the GSG unit transmits null- messages (SBAS message type:
MT63). An SBAS-compatible receiver should still be capable of seeing the SBAS signals,
but it will not find any useful information (range corrections, time offsets, etc.) in these mes-
sages.
Because of these reasons, SBAS scenarios run best with a live Internet connection. Fur-
thermore, since the aforementioned FTP sites store only a limited amount of SBAS
records, the start time of SBAS scenarios has to be chosen carefully:
Usually, SBAS records that are less than a year (EGNOS)/6 months (WAAS) old, can be
found on the FTP sites mentioned above. Therefore, it is advisable to select a start time
that is not older than one year for EGNOS scenarios, and not older than 6 months for
WAAS scenarios.
Moreover, the start time shall not be too close to the current time. For EGNOS, there can
be a one-day delay before the SBAS messages are published on the FTP site. For WAAS
the delay can possibly be longer (up to 3 or 4 days).
An Internet connection is not
always
needed, however: All downloaded ephemeris data
and SBAS data will be locally stored on the unit, once they have been downloaded. Hence,
the next time the same scenario runs, the ephemeris data and SBAS messages are read
from the local storage, not from the online ftp sites.
GSG will performs automatic clean-up of downloaded files, once the remaining free disc
space falls below 20% of the total disc space.
Note: The SBAS corrections are ‘applied backwards’ to the output GPS sig-
nals by adjusting the signal ranges.
It is also possible to download the EGNOS and WAAS files from the ftp servers, and select
them for use in the scenario: The file name holds the information on the applicable time &
date, which is NOT available in the content of the file (all time is relative), and must follow
these naming conventions:
For EGNOS : PRN<prn>_y<YYYY>_d<doy>_h<hour>.ems
For WAAS : Geo<prn>_<GPSWeek>_<dayOfWeek>
Note: WAAS files do not have a file extension.
Should the files downloaded from the ftp server do not meet these format requirements, it
will be necessary to rename the files accordingly.
3.5 "Select" Menu
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