Take off question

[ioannisg]

Hello.
I want to ask some questions about mavic pro that I don't understand.
If I take off for example from a building roof 20 meters from ground and I have set the RTH altitude to 20 meters what will it happen when RTH engage?
Also will it land safely in the roof?
Also what if I change home point during flight and from roof go to ground, will mavic recognize this and will it happen with RTH altitude which is set to 20 meters?
Can somebody explain please?

 

[msinger]

If you have the RTH altitude set to 20 meters, the Mavic will climb to 20 meters if the current altitude displayed in DJI GO is less than 20 meters. If the Mavic is already above 20 meters, then it'll return home at its current altitude. Be sure to check out the Mavic manual for more details about other less common RTH scenarios.

Since the Mavic does not know where the ground is located, it's going to think the top of the building is an altitude of 0 meters. If you fly above the building, the current altitude will be postive. If you fly below the building, the current altitude will be negative. If the current altitude is negative when RTH is initiated, the Mavic will climb to 0 meters and then up to your set RTH altitude.

Will the Mavic land safely on the roof? It will if there's enough room to land. If you're not using the Precision Landing feature, give your Mavic at least a 10 foot circle to account for some error when it's trying to land back at the takeoff spot.

 

[ioannisg]

If you have the RTH altitude set to 20 meters, the Mavic will climb to 20 meters if the current altitude displayed in DJI GO is less than 20 meters. If the Mavic is already above 20 meters, then it'll return home at its current altitude. Be sure to check out the Mavic manual for more details about other less common RTH scenarios.

So the solution is to check the dji app altitude after take off and then adjust RTH altitude,right?

The other parts of your reply are totally understood.
Thank you very much!

 

[Domagoj]

So the solution is to check the dji app altitude after take off and then adjust RTH altitude,right?

The other parts of your reply are totally understood.
Thank you very much!

If your RTH altitude is set (for example) to 50 meters and you take of from the roof which is at 20 m from the ground, your RTH altitude will be 70 m from the ground.

 

[DodgeP]

The altitude you take off from is considered ground level as far as your drone is concerned. Your settings will reflect that ground level reading, nothing else.

 

[ioannisg]

If your RTH altitude is set (for example) to 50 meters and you take of from the roof which is at 20 m from the ground, your RTH altitude will be 70 m from the ground.

Now I am confused.
So in app when I take off from roof which is 20 meters from ground I will see altitude 0 meters even if I fly away?

 

[DodgeP]

Now I am confused.
So in app when I take off from roof which is 20 meters from ground I will see altitude 0 meters even if I fly away?

Pay attention to what I'm telling you. When you start your drone, regardless of what altitude you're at, your drone sees that as ground level. Your RTH altitude will be based on where you powered up and locked a home point. Domagoj's comment is very misleading and incorrect. If you fly off the side of that roof and go below your take off point you'll be below ground level as far as your software is concerned.

 

[ioannisg]

Pay attention to what I'm telling you. When you start your drone, regardless of what altitude you're at, your drone sees that as ground level. Your RTH altitude will be based on where you powered up and locked a home point. Domagoj's comment is very misleading and incorrect. If you fly off the side of that roof and go below your take off point you'll be below ground level as far as your software is concerned.

I see.
Thank you!

 

[Domagoj]

Pay attention to what I'm telling you. When you start your drone, regardless of what altitude you're at, your drone sees that as ground level. Your RTH altitude will be based on where you powered up and locked a home point. Domagoj's comment is very misleading and incorrect. If you fly off the side of that roof and go below your take off point you'll be below ground level as far as your software is concerned.

Excuse me, but what in my comment is very misleading and incorrect?

 

[msinger]

So the solution is to check the dji app altitude after take off and then adjust RTH altitude,right?

Since the altitude is always 0 meters when your Mavic is sitting on the ground (or building in your case), you'll need to calculate the proper RTH altitude above that point. So, for example, if the tallest tree/obstacle is 20 meters above the top of the building, your RTH altitude will need to be set to a value higher than 20 meters so you can clear that tree/obstacle. I'd set it to at least 35 meters to add some extra padding since the current altitude displayed in DJI GO is just an estimate.

 

[ioannisg]

Ok. I understood all of you!
Thank you very much!
I am new and I was miss understandood the parameter which 0 meters for mavic is from where it took off. It isn't explained in the manual as far as I read.

 

[Doyleh13]

Ok. I understood all of you!
Thank you very much!
I am new and I was miss understandood the parameter which 0 meters for mavic is from where it took off. It isn't explained in the manual as far as I read.

They're both wrong...what you need to keep in mind is this...

Welcome to the forum, fellow pilot, where the views expressed by the post do not necessarily reflect those of management. Your actual mileage may vary. Void where prohibited.

 

[SeaComms]

There was something I noticed in one of the above posts too. It mentioned if you were above your RTH height it would drop to that height, it does not. If below RTH height it will rise to it when RTH is engaged, if it is already above RTH height it will remain at current height and return to home point and land.

Also in answer to one of your questions, if you take off from the roof your immediate height will show as 0 meters. If you then fly down to the ground your height will show -20 meters.