Not realy enough information to go on since you didn't state
what type of GPS system. It all depends on if the GPS system can be
configured either through an import mechanism, configuration files,
and so on.
You're going to have to dig a little for information on the
GPS system. Start with the Manufacturer and ask them directly,
google the product and see what others have done, etc. Assuming
it's not a closed system, you may even be able to open up some of
the configuration files to see how waypoints/push pins/markers are
stored.