I agree with Chris, you do not have to transmit GPS coordinates.
WSPR is a protocol for testing propagation, antennas and so on.
Using this digital mode you transmit your Callsign, first 4 chars of your locator and power in dBm.
Receiving stations report transmitter they are able to heard.
GPS usage could be to transform coordinate in Locator so you can made a beacon always transitting right locator and runtime updated.
WSJTX is a program written by John Taylor (WSPR creator and Physics Nobel Prize) for operating WSPR, JT65, FT8 etc. digital modes
Hope this helps,
Alessandro M. IU1ETR