Fishing Vessel Monitoring Systems: Past, Present and Future

VMS: Past, Present and Future 19
VMS
GPS simulator
Illustration 3.6: in the future, a GPS simulator might be used to input false data to
even a sealed terminal
whilst on the vessel.� There are about four companies in the world that build a
simulator that could be used for this spoofing purpose. It would take a very
sophisticated user to program the simulator but it could probably be done with
sufficient training.
The output from the simulator would be fed either directly into the GPS receiver
in place of the antenna connection or, it could be re-radiated from a small
antenna placed inside a metal container that covered the GPS antenna. This
latter approach would be difficult if the�GPS is integral with the antenna and also
if the antenna is also an INMARSAT transmitter. It would require somebody to
open up the antenna unit and detach the GPS antenna input to the receiver and
connect, in its place, the feed from the simulator.
To prevent this type of tampering, it would be possible to send part of the GPS
signal that would be ephemeral, and therefore impossible to simulate, as part of
the position report. This could be used to validate the report by comparing, for
instance, part of the broadcast ephemeris with a GPS receiver at the VMS
control centre. All that is needed is a message that changes regularly, to be sent
as part of the data verification, to make simulation nearly impossible.
The second approach is much easier. This less expensive approach involves
disabling the GPS receiver and feeding NMEA data into the position-reporting
transmitter from a PC on which NMEA messages could be generated. Interfacing