[time-nuts] Welnavigate GS720 GPS Simulator

Dieter Spaar spaar at mirider.augusta.de
Sat Jul 5 11:03:52 EDT 2014


does anyone know more about the GPS Simulators from Welnavigate ?
The company seems to longer exist for several years and not
much information can be found, besides some manuals on

I am especially interested in the software which controls the
hardware. From what I know so far the whole setup consists of
a PC running the software (Windows NT or Windows 2000 based,
some older ones used MS-DOS) which controls the hardware over
a GPIB interface. There were various hardware variants, e.g.
the GS 700, GS 720 or GS 1010, the main difference seems to be
the number of simulated satellites.

There is a patent from the company founder which describes the
hardware. I would like to find out the GPIB commands which control
the unit. From my understanding of the patent it should not be too
hard to write software which provides the required control data
(basically the 50 bps GPS data, code/phase offset and doppler shift)
for each simulated satellite.

Unfortunately the control logic of the GS 720 is completely FPGA
based, even the GPIB interface. So there is no firmware on the
GS 720 which would allow to reverse-engineer the GPIB commands.
Without knowing the GPIB commands or having access to the original
control software it is not possible to get the hardware do anything
usefull (maybe besides using the high-precision oscillator inside
the unit).

Thanks for any hints and best regards,
Dieter Spaar, Germany                           spaar at mirider.augusta.de

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