Since it's communicating with the rover, I was thinking it could use latency and/or Doppler effect as an input to narrow down the position, assuming the rover k

Since it's communicating with the rover, I was thinking it could use latency and/or Doppler effect as an input to narrow down the position, assuming the rover knew where it was, potentially by getting told by the satellites we have there. However I assume that would require special radio software, and they were using commercial Zigbee modules. In addition, I guess perhaps the helicopter and potentially rover wouldn't have accurate enough oscillators for this to be viable in any case.