Spectracom GSG-5 series, User Manual With Scpi Manual

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Skipped epochs
Note: One GSG epoch equals a 100 ms block of time.
The navigation receiver warning field will always be verified. An epoch will be skipped if…
…the field value is ‘V’, or
…there is no date/time data, or
…there is no position data.
File size
Note that NMEA trajectory files can become quite large if the sampling rate is high and a
large distance is covered. Simulation files uploaded to the GSG unit cannot contain more than
12000 epochs (~19 minutes RMC + GGA at 10 Hz).
If you start a scenario that uses an NMEA file with more than 12000 epochs, GSG will initiate
a dialog upon start of the scenario, asking you to either cancel the simulation execution, or to
truncate the NMEA trajectory file down to its first 12000 epochs.
Making a One-Line Trajectory
As the GSG unit uses the heading and speed information of the RMC sentences, only one (!)
NMEA sentence is actually required to describe a simple, continuous movement.
For example, the following one-line trajectory specifies a continuous north bound trajectory (as
the heading field is set to 0.0 degrees) at a speed of 77 knots.
$GPRMC,111150,A,6000.0000,N,0100.0000,E,77.000,0.0,010101,0.9,-
W,A*03
One-line trajectories like this can be easily be made by manually creating desired NMEA files.
The example above can be taken as a baseline, then edit speed and/or heading fields as
required. For the validity of the sentence, the last 2 digits contain a checksum of the data (XOR
of all bytes between $ and * symbols) – this checksum must be correct and can be calculated
with e.g., this online tool:
http://www.hhhh.org/wiml/proj/nmeaxor.html
. Note that the
NMEA messages, including the checksums, are case sensitive and should be given in
UPPERCASE even if the GSG unit (firmware version 3.00 and above) accepts messages in
lower case.
3.5.5 Ephemeris
The satellite constellations and the transmitted navigation data of each satellite are dynamically
built, once you start the scenario or the signal generation. The constellation and the navigation
data is based on
RINEX data
stored in the unit, or uploaded to the unit. The constellation orbits
can be refined by providing precise orbit information in
SP3 format
(for details, see below).
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User Manual GSG-5/6 Series Rev. 26
3.5 "Select" Menu