DORIS (Doppler Orbitography and Radiopositioning Intgrated by Satellite) is in some respects reverse GPS: the receivers are on satellites of opportunity, while the transmitters are on the ground. Many of the same principles that apply to GPS (including its high precision mode) also apply to DORIS.

DORIS exploits the Doppler effect: the frequency of the transmitted wave shifts when the transmitter and receiver are in relative motion. This effect can be used to solve for range change and range between the satellite receiver and the ground transmitter. The DORIS system is deployed on a number of satellites, including SPOT 2, 4 and 5, and ENVISAT. CSTARS receives data from all these satellites.

There are more than 50 DORIS ground transmitters, including one hosted by the Miami Geodesy Lab. While this number is far fewer than the number of GPS sites, some of the DORIS transmitters are in remote localities not covered by GPS. Hence, these sites can be very useful for plate motion studies. DORIS data was used in the plate motion studies of Norabuena et al. [1998; 1999] and Sella et al. [2002].