Can It Be Done? Elevations?

[hAltonJones]

I need to measure elevations on my property. The thought crossed my mind that the Mavic Mini app shows height and might somehow be used to do this. The problem is the height displayed is relative to the homepoint. If I set the homepoint and fly six feet above the ground to a point immediately over a five foot mound, it still shows that I'm flying at a six foot elevation. Anyone have any ideas for tricks on how to solve this challenge? Resetting homepoint in mid-flight? Any other thoughts?

 

[Chaosrider]

Yes, the lack of a true AGL reading is frustrating.

I bought Litchi, but I haven't tested it yet. However, if I'm understanding the features correctly, you can set waypoints in Litchi while flying, and Litchi will then, based on the GPS location of those waypoints, include the MSL altitude for that waypoint when it records it.

Has anyone done this? It looks like it should work, but I haven't tried it.

TCS

 

[db4476]

You could use a GNSS app on a smartphone instead of a drone, but then you would have to walk it.

Cheers!

 

[BigAl07]

How accurate is the DATA you're looking to capture?

 

[zeusfl]

Google Earth can give you a good estimate.

 

[zeusfl]

Now if you want a DEM. you can do a mission with Dronelink (mapping) and upload the pictures to be processed.

 

[snowghost]

Yes, the lack of a true AGL reading is frustrating.

I bought Litchi, but I haven't tested it yet. However, if I'm understanding the features correctly, you can set waypoints in Litchi while flying, and Litchi will then, based on the GPS location of those waypoints, include the MSL altitude for that waypoint when it records it.

Has anyone done this? It looks like it should work, but I haven't tried it.

TCS

I've used Litchi setting Waypoints altitude AGL, and it then calculates the drone altitude relative to Home Point. As such, you don't need to fly to record the different heights. Therefore Google Earth would be just as good.

 

[KB9Radio]

Yes, the lack of a true AGL reading is frustrating.

I bought Litchi, but I haven't tested it yet. However, if I'm understanding the features correctly, you can set waypoints in Litchi while flying, and Litchi will then, based on the GPS location of those waypoints, include the MSL altitude for that waypoint when it records it.

Has anyone done this? It looks like it should work, but I haven't tried it.

TCS

There's an option in litchi to set the altitude to AGL. It obtains it's AGL numbers from Google earth topo information, and needs to have access to that information (needs internet) during the flight so it knows what altitude to fly at. The altitude on DJI drones is done by a very sensitive barometric pressure sensor, it doesn't know where the ground is at all. It simply records what the pressure is when you turn it on and knows that as you go up, the pressure will be reduced. It's fairly accurate, but in no way exact.

 

[Dave Maine]

Note that most of the DJI drones Use a barometric altimeter which is not very accurate. There is not much you can do about it.

 

[snowghost]

There's an option in litchi to set the altitude to AGL. It obtains it's AGL numbers from Google earth topo information, and needs to have access to that information (needs internet) during the flight so it knows what altitude to fly at. The altitude on DJI drones is done by a very sensitive barometric pressure sensor, it doesn't know where the ground is at all. It simply records what the pressure is when you turn it on and knows that as you go up, the pressure will be reduced. It's fairly accurate, but in no way exact.

Litchi doesn't need Internet for the flight--just good GPS signal. All data is preloaded. Always give some altitude margin as the other posters have noted, the barometric sensor is not super accurate.

 

[wardtom084]

Or tie some tread/twine to the bottom of the drone, up and down with a measure.

 

[smashse]

Sign up for Measure Ground Control, or Drone Deploy free trial. Do a 3D map, what you are looking for is a DTM or DSM (Digital Terrain Map, or Digital Surface Map). The DTM shows elevations of the land, the DSM shows the elevations taking into consideration trees, buildings, etc. This will also require a fully automated flight (well not require, but it is much easier).

But, this is also only so good, because flying over tree tops the drone can't see what's below them, but a wide open mowed field is decently accurate.

.. Just reread that it is a Mavic Mini. Check the vendors to make sure it is supported. I think Drone Deploy does the Mini1 already, and they should on the Mini2 soon. But you can use Litchi or another automated service, and just use Drone Deploy or MGC for the processing.

 

[Disloyal Customer]

Sign up for Measure Ground Control, or Drone Deploy free trial. Do a 3D map, what you are looking for is a DTM or DSM (Digital Terrain Map, or Digital Surface Map). The DTM shows elevations of the land, the DSM shows the elevations taking into consideration trees, buildings, etc. This will also require a fully automated flight (well not require, but it is much easier).

But, this is also only so good, because flying over tree tops the drone can't see what's below them, but a wide open mowed field is decently accurate.

.. Just reread that it is a Mavic Mini. Check the vendors to make sure it is supported. I think Drone Deploy does the Mini1 already, and they should on the Mini2 soon. But you can use Litchi or another automated service, and just use Drone Deploy or MGC for the processing.

I have several DroneDeploy 3d maps created around the hilly, tree covered area that I fly. I'd love to take the point cloud from this area and create a DSM to use in Litchi where I could set my waypoints to be X feet above the highest obstacle within Y feet using that data. I don't think Litchi can support this yet.

I suppose I could create a DEM from the point cloud from DroneDeploy doing some kind of manual editing to get rid of trees, then use Litchi to fly X feet above the ground using the "above the ground" option for waypoints and just set it to a height higher than the trees.

 

[moldorf]

a few of the more expensive cameras for the bigger drones have laser range finders. Of course they are oriented the same direction as the camera so to range find the ground the camera would have to be pointing at it

at least that's the case if I understand how those range finders work

I'd wonder: how feasible would it be to have a laser range finder oriented thru the bottom of a drone...and how expensive?