Descend into canyon?

[chasm1a]

Can I send my Mavic 2 down into a canyon and expect to get it back? Does it measure vertical limit from the takeoff point and can it subtract descent from that? Or does it measure from the ground under it? Am I going to get, say, 500 feet down into a canyon and not be able to get out again? Has anyone experienced this? Thanks.

 

[bmwbob]

Can I send my Mavic 2 down into a canyon and expect to get it back? Does it measure vertical limit from the takeoff point and can it subtract descent from that? Or am I going to get, say, 500 feet down into a canyon and not be able to get out again? Has anyone experienced this? Thanks.

I sent my Mavic Mini 1000 feet down a canyon to ocean and back. I stayed about 400 feet AGL the entire way down.

 

[Meta4]

Can I send my Mavic 2 down into a canyon and expect to get it back? Does it measure vertical limit from the takeoff point and can it subtract descent from that? Or am I going to get, say, 500 feet down into a canyon and not be able to get out again? Has anyone experienced this?

I'm not sure why you think the drone might not come back but it makes no difference to the drone whether the altitude has a + or - sign in front of it.
Your Max Altitude Limit is a limit to how far above launch point you can fly.

And FYI .. you can always set a different Max Altitude Limit.

 

[chasm1a]

I sent my Mavic Mini 1000 feet down a canyon to ocean and back. I stayed about 400 feet AGL the entire way down.

Very good. That's what I wanted to know. Apparently the drone is not measuring its height relative to its launch point by sensors but by barometric pressure or GPS. Thanks.

 

[chasm1a]

I'm not sure why yiu think the drone might not come back but it makes no difference to the drone whether the altitude has a + or - sign in front of it.
Your Max Altitude Limit is a limit to how far above launch point you can fly.

And FYI .. you can always set a different Max Altitude Limit.

I was concerned that if the drone was measuring its vertical height from ground zero by, say, visual sensors, then if it flew out over a canyon at, say, ten feet vertical from launch point, and suddenly was over a canyon where the bottom was hundreds of feet lower, the drone would think it was over its vertical limit and limit upward travel so that if it got lower it couldn't get back up to launch elevation. Bmwbob showed me that he flew into a canyon and got out without problems. Apparently it measures altitude by barometric pressure or GPS and not by ground sensing.

 

[FoxhallGH]

The drone will measure negative altitude from your take-off point - but - the thing to be careful of is the drone losing GPS sat's due to the sides of the canyon blocking the sky. If the canyon is wide - not so much of a problem. But - if it's a narrow canyon, the drone can be restricted to seeing GPS sat's in a very narrow band of sky, and that can lead to it not being able to maintain stability ...

 

[Meta4]

I was concerned that if the drone was measuring its vertical height from ground zero by, say, visual sensors

The VPS sensors have a max range of 10 metres and are only useful when close to the ground.
Altitude is measured by barometric sensors.

 

[FoxhallGH]

I was concerned that if the drone was measuring its vertical height from ground zero by, say, visual sensors, then if it flew out over a canyon at, say, ten feet vertical from launch point, and suddenly was over a canyon where the bottom was hundreds of feet lower, the drone would think it was over its vertical limit and limit upward travel so that if it got lower it couldn't get back up to launch elevation. Bmwbob showed me that he flew into a canyon and got out without problems. Apparently it measures altitude by barometric pressure or GPS and not by ground sensing.

If you fly your Mavic up 10 ft from your take-off pad, then fly horizontally out over a 100 ft drop, the Mavic will still indicate its height as 10 feet. The Mavic will give you altitude data based on the take-off point, not on the space underneath it ...

 

[old man mavic]

just a couple of points to add when you are flying below the edge of a steep canyon or ravine,make sure that you keep the RC antennas flat sides pointing at the drone and make sure that you have a good safe position to fly from, as you will have to be looking over the edge to keep VLOS and finally beware of updraft from the wind it can be very powerful near the sides and could affect the drone

 

[bmwbob]

I was concerned that if the drone was measuring its vertical height from ground zero by, say, visual sensors, then if it flew out over a canyon at, say, ten feet vertical from launch point, and suddenly was over a canyon where the bottom was hundreds of feet lower, the drone would think it was over its vertical limit and limit upward travel so that if it got lower it couldn't get back up to launch elevation. Bmwbob showed me that he flew into a canyon and got out without problems. Apparently it measures altitude by barometric pressure or GPS and not by ground sensing.

It's measuring altitude from takeoff point using GPS, but just remember if you hit RTH, it's going to rise up to that set height above the RTH point! So I flew it back manually or it would have drained the battery rising to 1100 feet before coming home!

 

[Meta4]

It's measuring altitude from takeoff point using GPS

It uses the barometric sensor .. not GPS

 

[bmwbob]

It uses the barometric sensor .. not GPS

Guess I should have done a little research before posting GPS After thought logic tells me GPS is point on the ground not height above the ground!

 

[old man mavic]

GPS is having a receiver that can receive signals from sats up in space so it can know its position by working out how long the signal takes to travel from a given point in space and it use triangulation to get a fix ,it does not matter if it is in the air or on the ground ,the more sats that are locked the better the accuracy of that position,as the earth is constantly moving, so the amount of sats that are visible changes as well, as the sats stay in a fixed position above the earth

 

[chasm1a]

These are all great answers, especially for a newk like me. Thanks so much. But just to clarify, supposed I'm on top of a 500 foot building, and assuming no blockage of GPS by other buildings, I can fly my drone, descend to ground level and fly it back up to the launch spot with no problems. It won't regard the 500 foot ascent as violating the vertical limit. I shouldn't, however, use the RTH button from street level because RTH function is based on the launch location and would first bring the drone up to the launch level and then add additional vertical elevation before landing which would be a huge drain on the battery. Is this all right?

 

[old man mavic]

i fly a lot in mountainous topography and you just have to remember to allow for not only the distance you are from the home point, but also how far below the home point you are at any given time ,when you fly over fairly flat ground then you have the benefit of the wind behind you to help return ,and the fact that you can descend at the same time which uses less battery as well ,returning from say 500ft distance and -300 ft below the home point will require a lot more battery, as you will need more throttle to achieve forwards ,and ascent momentum for a given distance so in these circumstances plan you flight so as to have more battery charge left to give yourself a safety buffer

 

[chasm1a]

Good advice. Thanks!

 

[alopeznj]

I'm not sure why yiu think the drone might not come back but it makes no difference to the drone whether the altitude has a + or - sign in front of it.
Your Max Altitude Limit is a limit to how far above launch point you can fly.

And FYI .. you can always set a different Max Altitude Limit.

Thanks. I had this question myself and never posted. Going to drop it down a dead Volcano . When I can get there of course. Vacation Cancelled

 

[Meta4]

But just to clarify, supposed I'm on top of a 500 foot building ... I can fly my drone, descend to ground level and fly it back up to the launch spot with no problems. It won't regard the 500 foot ascent as violating the vertical limit.

That's been clarified already in this thread.

I shouldn't, however, use the RTH button from street level because RTH function is based on the launch location and would first bring the drone up to the launch level and then add additional vertical elevation before landing which would be a huge drain on the battery. Is this all right?

No .. you can use the RTH function.
But if you had a ridiculous and unnecessary RTH height set, and you left RTH to do its thing, RTH would climb to a ridiculous height above the launch point before descending to land at home.
BUT .. you can set a practical RTH height AND you can cancel RTH and resume control and bring the drone home and/or land it at any time as long as you have control signal.

 

[Searat290]

Guess I should have done a little research before posting GPS After thought logic tells me GPS is point on the ground not height above the ground!

Hi, minor correction, gps can indeed determine altitude. It may not be used for that by the Mavic as barametric is quicker to respond.