Dumb Question About Altitudes - Flying Into Canyons?

[CageyWhite]

Hello Everyone:

I'm (obviously) a very new pilot and I have a question.

I'm going to be flying at a point where I will take off from a certain spot and then descend into a relatively deep where I will take pictures and record some video. So my question is, will this create issues with the GPS or other censors in the drone?

For example, if I take off at one point and then descend into a canyon and fly in an area that is, say 100 feet lower than the point where I took off, will that create any problems? If I hit RTH, will the drone fly up to a point that is equal to where the drone was launched (while hovering in the canyon) and then fly HIGER to the point that I set in the controller (based on where I launched the drone) and then come home? Or will it ascend the number of feet that I set in the controller and get stuck because it's still in the canyon (because it didn't compensate for the initial descent into the canyon)?

Anyway, are there any particular steps I should take under this scenario? Thanks, and sorry for the dumb question.

 

[Meta4]

If I hit RTH, will the drone fly up to a point that is equal to where the drone was launched (while hovering in the canyon) and then fly HIGHER to the point that I set in the controller (based on where I launched the drone) and then come home?

Yes ... that's how things work, because all heights are based on Home = zero

Anyway, are there any particular steps I should take under this scenario? Thanks, and sorry for the dumb question.

If the canyon is a wide valley (like the grand canyon) your drone would have a good view of lots of the sky and no GPS issues.

But if it's a narrow ravine that blocks out most of the sky, it will also block out most of the sky (and the satellites) and that can create a hazard for you.
It's mentioned on p43 of your manual.

Height is restricted to 16 ft (5 m) when the GPS signal is weak and Downward Vision System is activated. ​

Height is restricted to 98 ft (30 m) when the GPS signal is weak and Downward Vision System is inactive.​

In other words, if you have poor or weak GPS, your drone will not be able to climb more than 16 feet.
That's not a problem going down, but if your drone's downward facing sensors see something below them, due to poor programming, the zero height is reset and you might not be able to bring it back up again.

This is an uncommon situation, but has been responsible for the loss of a few drones.

 

[MARK (LI)]

Something else to be aware of is if the canyon walls are steep it may become difficult to maintain staying within 400FT AGL

 

[Grant Angus Vietnam]

Hello Everyone:

I'm (obviously) a very new pilot and I have a question.

I'm going to be flying at a point where I will take off from a certain spot and then descend into a relatively deep where I will take pictures and record some video. So my question is, will this create issues with the GPS or other censors in the drone?

For example, if I take off at one point and then descend into a canyon and fly in an area that is, say 100 feet lower than the point where I took off, will that create any problems? If I hit RTH, will the drone fly up to a point that is equal to where the drone was launched (while hovering in the canyon) and then fly HIGER to the point that I set in the controller (based on where I launched the drone) and then come home? Or will it ascend the number of feet that I set in the controller and get stuck because it's still in the canyon (because it didn't compensate for the initial descent into the canyon)?

Anyway, are there any particular steps I should take under this scenario? Thanks, and sorry for the dumb question.

Will RTH at the altitude you set at your Takeoff point

 

[BigAl07]

I was recently flying for a client who owned a cabin nestled on a mountain ridge above some amazing water falls down in the canyon below. I flew down into the canyon to capture the falls for their promotional video and while down in the canyon I lost satellite connections. The aircraft fell out of GPS mode and went into AttiMode. The aircraft was then in a sort of "manual mode" which was a concern because the wind currents in the valley were more than I realized when the aircraft was stabilized with GPS. Fortunately manual mode is how I learned (long before Gyros and GPS guidance) so it was natural to counter-act the wind and get the video/images needed. When it was time to ascend it hit a " AttiMode ceiling" where I could not ascend any higher. I was lucky enough to have room to fly along the river to where the canyon opens up and regain sufficient satellite count to go back into GPS mode and then to ascend back to my location. Otherwise I would have been required to make a landing down in the valley and hiked down to retrieve the aircraft (if I was lucky).

The valley/canyon mentioned above is a narrow and HEAVILY forested area which both leads to dismal GPS potential. See image below for reference . . . .

 

[Karlewski]

To further these points, that are solid advice. It is not how low below your home point that matters. It is how deep into the canyon you fly. Going very deep into the canyon is DANGEROUS. As mentioned, the view to the open sky and satellites is closing and once you loose satellite line of sight GPS is gone and all functions along with it, not to mention you may well loose line of sight and you're radio contact as well if you did not position your self correctly to maintain it. Unless you are quite familiar with all of these concepts AND flying your drone manually, I would strongly suggest staying out of narrow canyons. You still can still safely fly over and above the rim, top down shots, or along the rim for a side shot but deep in a narrow canyon IS the worst place to be. . . I did both styles here

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knowing the risks. If you just have to fly deep in a canyon, like I did, just keep it in easy line of sight and AWAY from the canyon walls knowing you may have to fly without any GPS positioning assistance. Even with decent satellite reception flying in a canyon is difficult, easy to loose orientation and hit a wall. . . .

 

[Deleted member 103366]

What point/height does the drone use as its base point for the maximum climb when GPS is lost whilst IN FLIGHT?
I can think of two possibilities, firstly the point/height at which the GPS signal was lost and the other being the lowest point measured by the drone

 

[Karlewski]

It uses the home point.

 

[CageyWhite]

OK, I got it. Thanks to everyone who responded. I should note that the canyon I want to film is wide and should not have any obstructions to a GPS connection. To clarify (sorry I didn't put this in my original post), the canyon I want to film is actually part of a man-made reservoir that was used for water storage for California. That reservoir is less than 40% full now due to our drought (and and the fact that our politicians refused to invest in new water storage infrastructure as the population grew), so I wanted to take some shots to compare the water levels now versus where they were when the reservoir was full. So I would be flying into the reservoir in space that would normally be filled with water. So, it's a wide, open space that will, however, be lower than the launch point.

I think I have this and know the precautions I need to take. As always, THANK YOU!

 

[Viva Terlingua]

It uses the home point.

Can it still use it after gps is lost?

 

[Meta4]

Can it still use it after gps is lost?

The zero altitude is independent of GPS.
It's recorded before the drone acquires GPS and stays even if GPS is lost.
But RTH won't work without GPS.

 

[Meta4]

I think I have this and know the precautions I need to take.

Sounds like no special precautions are necessary.
It makes no difference to the drone whether the altitude has a + or - sign in front of it.

 

[Marcass Carcass]

Oh, btw, flying over water is another can of worms..........

 

[Meta4]

Oh, btw, flying over water is another can of worms..........

It's not really ... but it is another current thread:

"Over Water" mode for drones

I've spent this past weekend reading the tragic stories of Drone splashdowns, and wonder if DJI could develop a "Smart mode" to disable, or adapt the vertical sensors to deal with water issues. Yes, I'm aware that some (but not all) DJI AC allow this by a menu click. I'm thinking, a mode that...

mavicpilots.com

 

[tlswift58]

OK, I got it. Thanks to everyone who responded. I should note that the canyon I want to film is wide and should not have any obstructions to a GPS connection. To clarify (sorry I didn't put this in my original post), the canyon I want to film is actually part of a man-made reservoir that was used for water storage for California. That reservoir is less than 40% full now due to our drought (and and the fact that our politicians refused to invest in new water storage infrastructure as the population grew), so I wanted to take some shots to compare the water levels now versus where they were when the reservoir was full. So I would be flying into the reservoir in space that would normally be filled with water. So, it's a wide, open space that will, however, be lower than the launch point.

I think I have this and know the precautions I need to take. As always, THANK YOU!

2 things:

Make absolutely sure your "homepoint" sets near you prior to flying out; otherwise RTH is hit or miss.

Be absolutely sure you can fly in that area. In NC many watershed reservoirs are off limits to anyone except proper personnel. So, that being said - make sure Aloft or other Apps show clear flying area.

Having flown into a canyon / gorge it is extremely easy to lose sight of the drone. That little gray drone seems to disappear from view quite easily. I did not have any GPS issues as the gorge was pretty wide and I did not get super close to the bottom - probably 450-500 below where I was at. It's a thrill and nerve wracking as well. If it's an Air2 - if shooting video - highly advise to run the zoom up to maybe 2-2.5 so that you can maintain a healthy altitude and still get some decent close in video. Sadly, zoom does not work in pic mode.

If you don't have drone insurance - buy it before you try it. State Farm has it and about $75 or less for a year. DJI probably would not cover a loss / crash if you have their coverage.

 

[LA 2020]

Hello Everyone:

I'm (obviously) a very new pilot and I have a question.

I'm going to be flying at a point where I will take off from a certain spot and then descend into a relatively deep where I will take pictures and record some video. So my question is, will this create issues with the GPS or other censors in the drone?

For example, if I take off at one point and then descend into a canyon and fly in an area that is, say 100 feet lower than the point where I took off, will that create any problems? If I hit RTH, will the drone fly up to a point that is equal to where the drone was launched (while hovering in the canyon) and then fly HIGER to the point that I set in the controller (based on where I launched the drone) and then come home? Or will it ascend the number of feet that I set in the controller and get stuck because it's still in the canyon (because it didn't compensate for the initial descent into the canyon)?

Anyway, are there any particular steps I should take under this scenario? Thanks, and sorry for the dumb question.

What you are attempting is tricky because it's hard to judge altitude when you are above the target. The RTH measures from where you took off and where your RTH altitude setting is. If you fly negative altitude the RTH will still go up to the altitude you have set above the takeoff point. What I do to fly negative if possible use the drone to fly down to an altitude of a feature and keep track of that negative altitude so you don't go too low when you make your photo flight.

 

[paparatzy]

What you are attempting is tricky because it's hard to judge altitude when you are above the target. The RTH measures from where you took off and where your RTH altitude setting is. If you fly negative altitude the RTH will still go up to the altitude you have set above the takeoff point. What I do to fly negative if possible use the drone to fly down to an altitude of a feature and keep track of that negative altitude so you don't go too low when you make your photo flight.

Thanks for the clarity. However, your last statement about going too low, for me, could use some clarity as a new pilot. I've only flown my Air2s 10 times in practicing and today will be flying over acreage property that borders on the Crooked River Canyon, which is about 500' deep, but quite wide open.

My RTH point will be on top somewhere near the home and will set the RTH altitude to 100'. I've yet to take-off from one level and fly out over a canyon and had questions about what the drone would do when suddenly the altitude went from 100' to 600' (canyon floor).

After reading this thread, if my understanding is correct, the altitude is measured from RTH ground zero and the drone won't change it's altitude on it's own even though it is now 600' high and over the 400' altitude limit. Yes?

And back to your statement, keeping track of the negative altitude was referring to crashing the drone, not an inability to fly back out?

 

[Deleted member 103366]

When outside/above the range of the VPS sensors on the bottom of the drone, the drone has not the slightest concern about its height above the ground directly beneath it. All it is concerned about/with is the height above, or below, the take off point. So your 3rd paragraph understanding is correct.


BUT be wary when descending into the canyon and keep a good, watchful eye on the satellite count.
If the drone loses enough satellites it will not know where it is and will therefore NOT be able to RTH. Indeed it may also enter a situation where its ability to climb is SEVERELY restricted, look up the low GPS height restrictions in the App.
I have seen at least one thread where this happened, i.e. GPS was lost well down in a valley and the drone WOULD NOT climb back into GPS lock. The poster had to fly it further along the valley to a lower part of the valley's rim and land it there.

 

[paparatzy]

When outside/above the range of the VPS sensors on the bottom of the drone, the drone has not the slightest concern about its height above the ground directly beneath it. All it is concerned about/with is the height above, or below, the take off point. So your 3rd paragraph understanding is correct.


BUT be wary when descending into the canyon and keep a good, watchful eye on the satellite count.
If the drone loses enough satellites it will not know where it is and will therefore NOT be able to RTH. Indeed it may also enter a situation where its ability to climb is SEVERELY restricted, look up the low GPS height restrictions in the App.
I have seen at least one thread where this happened, i.e. GPS was lost well down in a valley and the drone WOULD NOT climb back into GPS lock. The poster had to fly it further along the valley to a lower part of the valley's rim and land it there.

My confidence level is SLOWLY gaining altitude, so I have no plans to fly down into the canyon and will just fly out over the canyon, turn, and take photos of the home. This thread and PhillusFoggg has given me confidence for today's shoot and actually has me looking forward to it.

 

[Deleted member 103366]

My confidence level is SLOWLY gaining altitude, so I have no plans to fly down into the canyon and will just fly out over the canyon, turn, and take photos of the home. This thread and PhillusFoggg has given me confidence for today's shoot and actually has me looking forward to it.

Note, if you fly out over a 500ft deep canyon at a height that is 100ft above the canyon rim then you will, strictly speaking I think, be flying at an illegal height.
As far as I am aware the drone ceiling in the US is 400ft above the ground directly beneath the drone (AGL) and you would be at 600ft AGL and possibly into manned aircraft air space.
Said another way, imagine that a 400ft long weighted string was attached to the bottom of the drone, that string must ALWAYS be it contact with the ground.
Whether or not a manned aircraft would be flying in the canyon at 500ft+ canyon AGL i.e. ground level and up for you is a different matter.