- Joined
- Sep 20, 2017
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- Age
- 79
Recently I had a scare flying my Mavic Pro. I took it to the village of Kakkopetia in the Trodos Mountains in Cyprus. Once my RC display showed I was in GPS Mode I took off, then flew around the village for about 12 minutes. Normally I will fly back to the landing manually, but in this case the drone was into sun and difficult to see, so I used the Come Home button.
Unusually, I did not hear my Mavic approaching overhead, despite the height display showing it was descending to land. At first I spotted what I thought to be a bird, but it was in fact my drone about to descend into a built up area at least 200 yards away. I abandoned the Come Home and managed to fly it back to a successful landing.
Analysis of the flight recorder showed that the home position had not been updated for a full 30 seconds after take off, thus recording the home position 200 yards away from where I took off. So what does GPS Mode on the RC really mean? It would seem that it does not imply that an accurate fix has been obtained. In this case, the terrain would have made less satellites visible, and yes I did not hear 'The Home Point Has Been Updated' message, but if that message is spoken through my mobile phone and the volume is down, then maybe not surprising.
GPS Mode certainly creates stability in the post take off hover, but what is the drone really using at this stage? Is it keeping station by ground image comparison or by a GPS fix? If the latter were true, I would expect the Home Position to respect that fix and not move dramatically as in this case. My only explanation is that a poor fix was obtained initially that was lost after take off then regained 30 seconds later. Would it not be better if the RC showed GPS Mode only after the fix was good enough to nail the home position? Subsequent tests have shown a return to normal operation.
Any thought please on how GPS Mode really works?
Unusually, I did not hear my Mavic approaching overhead, despite the height display showing it was descending to land. At first I spotted what I thought to be a bird, but it was in fact my drone about to descend into a built up area at least 200 yards away. I abandoned the Come Home and managed to fly it back to a successful landing.
Analysis of the flight recorder showed that the home position had not been updated for a full 30 seconds after take off, thus recording the home position 200 yards away from where I took off. So what does GPS Mode on the RC really mean? It would seem that it does not imply that an accurate fix has been obtained. In this case, the terrain would have made less satellites visible, and yes I did not hear 'The Home Point Has Been Updated' message, but if that message is spoken through my mobile phone and the volume is down, then maybe not surprising.
GPS Mode certainly creates stability in the post take off hover, but what is the drone really using at this stage? Is it keeping station by ground image comparison or by a GPS fix? If the latter were true, I would expect the Home Position to respect that fix and not move dramatically as in this case. My only explanation is that a poor fix was obtained initially that was lost after take off then regained 30 seconds later. Would it not be better if the RC showed GPS Mode only after the fix was good enough to nail the home position? Subsequent tests have shown a return to normal operation.
Any thought please on how GPS Mode really works?
