UKHeliBob:
If the number of data points to be logged is not large then the data could be saved to EEPROM and read back later. Alternatively the data could be saved to an SD card but that would require extra hardware.If there is no issue in using extra hardware then a GPS receiver on the drone would allow you to record the absolute position of the drone and/or to send it back to the RC transmitter.
I don't have a feeling yet about how many data points could be saved on the EEPROM, but it's worth a try before buying an SD-card module.
I already have an DJI Inspire with GPS. The thing is that I want to add an Arduino to it and send a signal from the transmitter to receiver. But how am I able to check if the receiver is receiving the signal that I'm sending at around 500m?