Flying over deep canyons risk

[cloneme]

I am a new owner of a mavic 2 pro and have flown it a few times successfully . I would like to fly it over my daughter's property (340 acres) but one boundary is a sheer cliff some 300m to a river and we would like to be able to get a video over the edge. My question is, would flying over a sudden drop which would mean the drone's senses that the height has gone from say 100m to 400m would there be a correction and the drone would drop?

 

[sar104]

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

 

[Meta4]

My question is, would flying over a sudden drop which would mean the drone's senses that the height has gone from say 100m to 400m would there be a correction and the drone would drop?

Your drone has no sensors that could tell that it's height above the ground has changed from say 100m to 400m.
Plus .. it's a flying machine, not a following terrain machine.
It will act just like a bird or airplane flying past a cliff edge.

 

[old man mavic]

make sure that as you fly out from the edge and descend that you keep the controller pointed at the drone and be careful near to the edge dont let the drone out of your site as it will most likely do a return to home as it will think the signal has been lost

 

[FormerMember07122019_2]

old man mavic - you beat me by a minute. I was about to post a similar concern.

 

[cloneme]

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

Thank you for your reply and have taken note, I think I might just stick to the edge

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

 

[cloneme]

Thank you very much to everyone for your replies, although you have made me feel more confident, I think I might just stick to the edge for now and try it out on a smaller retriveable drop before I go for the big one I have learnt a lot in this forum and very gratefull for all the technical information members contribute.

 

[AMann]

As long as it is not under an overhang while it was flying down inside the canyon, if it does a return to home it would rise to whatever setting above the starting point it was set to before heading straight out towards home. You would probably be able to regain contact after it rises out of the canyon by itself. One issue would be that you may lose GPS while down there, which means it may drift if there’s any wind into a side wall.

 

[Spike151]

The one thing to watch out for is updrafts on the cliff face, you may get a strong wind travelling vertically upwards which can overwhelm the motors. I have seen at least half a dozen “ I lost my drone or crashed my drone” due to cliffs

 

[bliksem]

Wind and air turbulence could be a problem

 

[Bobvt]

No - the aircraft VPS system may notice that the ground has vanished, but the aircraft references its altitude to the home point, not to the ground it is flying over. It will be unaffected by flying over a 300 m cliff. I'd watch out for up- or down-drafts though.

Sar105 you are awesome, I've been waiting to ask this exact question myself,thank you very much

 

[Drbobk]

Is the altitude strictly barometric? Why doesn’t it use GPS for altitude as well? (Not referencing the cliff, but just in general...aircraft now use GPS for instrument approaches, and I assume that uses GPS altitude input.)

 

[old man mavic]

Is the altitude strictly barometric? Why doesn’t it use GPS for altitude as well? (Not referencing the cliff, but just in general...aircraft now use GPS for instrument approaches, and I assume that uses GPS altitude input.)

the altitude reading shown on the screen is the height above the take off point, it has no bearing on the altitude at any other point in the flight,it is a reference point for the return to home altitude that is set in the app,if you fly down from a high take off point then the height on the screen will actually show a negative figure, it is only when very close to the ground that the bottom sensors detect the distance from the ground ,the barometer is not that accurate as it can be affected by wind speed and barometric pressure the GPS gives the mav a fix in space from the sats that it locks on to nothing to do with its actual height above the ground @Drbobk

 

[sar104]

Is the altitude strictly barometric? Why doesn’t it use GPS for altitude as well? (Not referencing the cliff, but just in general...aircraft now use GPS for instrument approaches, and I assume that uses GPS altitude input.)

It's not completely clear whether or not the FC incorporates GPS altitude data into the sensor fusion algorithm (which definitely uses the barometric pressure and accelerometer data) at any gain level. My tentative conclusion is that it does not, because if you compare the GPS and OSD altitudes it is apparent that the OSD altitude follows the barometric pressure rather than the GPS altitude.

 

[AMann]

It's not completely clear whether or not the FC incorporates GPS altitude data into the sensor fusion algorithm (which definitely uses the barometric pressure and accelerometer data) at any gain level. My tentative conclusion is that it does not, because if you compare the GPS and OSD altitudes it is apparent that the OSD altitude follows the barometric pressure rather than the GPS altitude.

I’m glad it uses relative barometric pressure (as compared to the home point) - GPS altitude is worthless when you want any accuracy better than +-20m.

When we backpack, I often just use my altimeter to pinpoint my location on a topo, way better than GPS, especially if in a canyon.

 

[AMann]

Is the altitude strictly barometric? Why doesn’t it use GPS for altitude as well? (Not referencing the cliff, but just in general...aircraft now use GPS for instrument approaches, and I assume that uses GPS altitude input.)

Standard GPS is only good to +-20m for elevation, even with WASP correction.

 

[sar104]

I’m glad it uses relative barometric pressure (as compared to the home point) - GPS altitude is worthless when you want any accuracy better than +-20m.

When we backpack, I often just use my altimeter to pinpoint my location on a topo, way better than GPS, especially if in a canyon.

Actually the GPS altitude data are very good - typically to within a couple of meters. The barometric measurement is probably a bit more robust for those situations where the VDOP is larger, but in absolute terms the GPS altitude is much more accurate.

 

[Mavic-Max]

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[AMann]

Actually the GPS altitude data are very good - typically to within a couple of meters. The barometric measurement is probably a bit more robust for those situations where the VDOP is larger, but in absolute terms the GPS altitude is much more accurate.

How accurate do you mean? Consumer grade GPS, even with GLONASS and with WASP correction do not measure it accurately with an error margin of less than +- 10m. Even a cheap hand held barometer can measure relative elevation changes to closer than 1m. Ive used survey grade Trimbles that couldn’t do it reliably without stayng on point for several minutes and having to do post-processing later with the data to get that kind of accuracy.

 

[sar104]

How accurate do you mean? Consumer grade GPS, even with GLONASS and with WASP correction do not measure it accurately with an error margin of less than +- 10m. Even a cheap hand held barometer can measure relative elevation changes to closer than 1m. Ive used survey grade Trimbles that couldn’t do it reliably without stayng on point for several minutes and having to do post-processing later with the data to get that kind of accuracy.

As I said - it's typically 2 - 3 meters with the modern chips and > 12 satellites. That's not really surprising since the theoretical average vertical error is 1.5 times the horizontal error. In the air these receivers typically do very well because they have such a good sky view.