You must look for NMEA data simulator and propagate that through your sim data bus of any known standard from RS232 and up...to AIRINC 429 level.
The real GPS data simulation within closed Faraday cage is possible too.
Have some experience using this SW package
https://github.com/osqzss/gps-sdr-sim
On Lime SDR USB Hardware, with some additional SW blocks, you can can "move" around easy.