Understanding "RTH At Current Altitude"

[JAW]

I might be a little slow on the uptake, but after several readings of the manual I still could not get my arms around how the RTH At Current Altitude setting in GO4 affects things. What I found in the Spark pilot's forum was the following explanation which cleared things up. I do hope it is correct:
NOTE after comparing the altitudes in the following which are from the Spark manual to the M2 manual altitudes, there are some slight differences. But the principles remain the same.


Two settings in DJI GO 4 app are relevant for how RTH behaves after being triggered

- Setting #1: The “Return-To-Home Altitude” setting, i.e. pre-set RTH altitude
- Setting #2: The “RTH at Current Altitude” option

Once the RTH is triggered there are four cases dependant on the drone's distance to the recorded home point to consider.

Case #1 - The drone's distance to the recorded home point is less than 3m
In this case the drone will descend to land immediately from its current altitude and position.
Note: The Current Altitude option is ignored in this case. The drone will not ascend to the pre-set altitude even if the Current Altitude option is disabled.

Case #2 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option disabled.
The drone will immediately descend to land from its current altitude and position.

Case #3 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option enabled
The drone will check its altitude. If its current altitude is above 2.5m the drone will RTH at its current altitude immediately. If the altitude is less than 2.5m it will ascend to 2.5m first and then start to RTH.

Case #4 - The drone's distance to the recorded home point is greater than 20m
The drone will check its current altitude. If the drone is higher than the pre-set altitude it will start to RTH at the current altitude immediately. If it is lower than the pre-set altitude it will ascend to the pre-set altitude first before starting to RTH.
Note: The Current Altitude option is ignored in this case. The drone will always return at the pre-set altitude at a minimum.

Conclusion: The Current Altitude option setting is only taken in account in a scenario where the drone's distance to the recorded home point is in the 3m to 20m bracket. In all other cases the Current Altitude option setting is disregarded. It is perfectly safe to enable the Current Altitude option to avoid immediate landing in case of an RTH event in the 3m to 20m range. If the drone is further out it always returns at the pre-set altitude at a minimum.

 

[brett8883]

I might be a little slow on the uptake, but after several readings of the manual I still could not get my arms around how the RTH At Current Altitude setting in GO4 affects things. What I found in the Spark pilot's forum was the following explanation which cleared things up. I do hope it is correct:
NOTE after comparing the altitudes in the following which are from the Spark manual to the M2 manual altitudes, there are some slight differences. But the principles remain the same.


Two settings in DJI GO 4 app are relevant for how RTH behaves after being triggered

- Setting #1: The “Return-To-Home Altitude” setting, i.e. pre-set RTH altitude
- Setting #2: The “RTH at Current Altitude” option

Once the RTH is triggered there are four cases dependant on the drone's distance to the recorded home point to consider.

Case #1 - The drone's distance to the recorded home point is less than 3m
In this case the drone will descend to land immediately from its current altitude and position.
Note: The Current Altitude option is ignored in this case. The drone will not ascend to the pre-set altitude even if the Current Altitude option is disabled.

Case #2 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option disabled.
The drone will immediately descend to land from its current altitude and position.

Case #3 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option enabled
The drone will check its altitude. If its current altitude is above 2.5m the drone will RTH at its current altitude immediately. If the altitude is less than 2.5m it will ascend to 2.5m first and then start to RTH.

Case #4 - The drone's distance to the recorded home point is greater than 20m
The drone will check its current altitude. If the drone is higher than the pre-set altitude it will start to RTH at the current altitude immediately. If it is lower than the pre-set altitude it will ascend to the pre-set altitude first before starting to RTH.
Note: The Current Altitude option is ignored in this case. The drone will always return at the pre-set altitude at a minimum.

Conclusion: The Current Altitude option setting is only taken in account in a scenario where the drone's distance to the recorded home point is in the 3m to 20m bracket. In all other cases the Current Altitude option setting is disregarded. It is perfectly safe to enable the Current Altitude option to avoid immediate landing in case of an RTH event in the 3m to 20m range. If the drone is further out it always returns at the pre-set altitude at a minimum.

Be advised this only applies to spark. The mavic will always RTH at or above the RTH altitude. If it’s close it will auto-land instead of RTH but it will never RTH below the the RTH altitude.

Edit: I was corrected in that if the “ use current altitude” option is enabled this might not be the case.

 

[msinger]

The mavic will always RTH at or above the RTH altitude. If it’s close it will auto-land instead of RTH but it will never RTH below the the RTH altitude

It depends how close the Mavic is to the home point. It can also fly home at its current altitude (which could be below the RTH Altitude). See your Mavic manual for more details.

 

[JAW]

From the current Mavic2 manual:

b. If the aircraft is between 5 m and 20 m from the Home Point when the RTH procedure begins:
i. If the RTH at Current Altitude option is enabled the aircraft flies to the Home Point at the current altitude, unless the current altitude is less than 2 m, in which case the aircraft ascends to 2 m and then flies to the Home Point at a speed of 3 m/s.
ii. If the RTH at Current Altitude option is disabled, the aircraft lands immediately.

 

[Air_Joe]

Be advised this only applies to spark. The mavic will always RTH at or above the RTH altitude. If it’s close it will auto-land instead of RTH but it will never RTH below the the RTH altitude

Thats a very ‘safe’ feature, glad dji tot of this,

1) does it mean when we are on the top of a hill flying towards the foot, it will go upwards and rth, when we hit the rth button?

2) any idea does mavic air react the same?

 

[msinger]

does it mean when we are on the top of a hill flying towards the foot, it will go upwards and rth, when we hit the rth button?

There are many factors that can come into play here. It depends on the aircraft's current altitude, distance, whether or not it's using its GPS data, and/or what caused RTH to be initiated. The DJI manual contains a lot of great information on this topic.

 

[brett8883]

From the current Mavic2 manual:

b. If the aircraft is between 5 m and 20 m from the Home Point when the RTH procedure begins:
i. If the RTH at Current Altitude option is enabled the aircraft flies to the Home Point at the current altitude, unless the current altitude is less than 2 m, in which case the aircraft ascends to 2 m and then flies to the Home Point at a speed of 3 m/s.
ii. If the RTH at Current Altitude option is disabled, the aircraft lands immediately.

You are correct and I’ve corrected my message above. Sorry bout that.

 

[msinger]

You are correct and I’ve corrected my message above. Sorry bout that.

The Mavic Pro and Mavic Air can also fly home below the RTH Altitude.

Since this topic is in the general section of the forum, anyone who stumbles upon it should really read the DJI manual closely since all of the Mavic models have different RTH procedures.

 

[Arce101]

I was wondering if you put on smart rth will it try to avoid obstacles on its way back if it’s below a tree line etc

 

[Arce101]

What is smart rth actually do?

 

[msinger]

What is smart rth actually do?

"Smart RTH" is just the process of you manually initiating RTH using the RTH button on the remote controller or the icon on the left side of DJI GO.

If you're referring to the "Smart Return-to-Home" setting (a setting with a confusingly similar name), that will auto initiate RTH when the drone determines it only has enough battery power to make it back to the home point. When RTH is initiated that way, DJI GO will display a prompt to let you know RTH is going to be initiated and will give you 10 seconds to cancel it. If you do nothing, the Mavic will return home.

 

[JAW]

What is smart rth actually do?

Pages 15-19 of the new manual, V 2.0, will tell you everything about RTH:

Mavic 2 - Product Information - DJI

The Mavic 2 is DJI's flagship consumer drone built for pros and enthusiasts. Discover more about the Mavic 2 Pro and Mavic 2 Zoom with specs, FAQs, video tutorials, guides, and user manuals. Learn more at DJI.com.

www.mavichelp.com

 

[Joe4flight]

I might be a little slow on the uptake, but after several readings of the manual I still could not get my arms around how the RTH At Current Altitude setting in GO4 affects things. What I found in the Spark pilot's forum was the following explanation which cleared things up. I do hope it is correct:
NOTE after comparing the altitudes in the following which are from the Spark manual to the M2 manual altitudes, there are some slight differences. But the principles remain the same.


Two settings in DJI GO 4 app are relevant for how RTH behaves after being triggered

- Setting #1: The “Return-To-Home Altitude” setting, i.e. pre-set RTH altitude
- Setting #2: The “RTH at Current Altitude” option

Once the RTH is triggered there are four cases dependant on the drone's distance to the recorded home point to consider.

Case #1 - The drone's distance to the recorded home point is less than 3m
In this case the drone will descend to land immediately from its current altitude and position.
Note: The Current Altitude option is ignored in this case. The drone will not ascend to the pre-set altitude even if the Current Altitude option is disabled.

Case #2 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option disabled.
The drone will immediately descend to land from its current altitude and position.

Case #3 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option enabled
The drone will check its altitude. If its current altitude is above 2.5m the drone will RTH at its current altitude immediately. If the altitude is less than 2.5m it will ascend to 2.5m first and then start to RTH.

Case #4 - The drone's distance to the recorded home point is greater than 20m
The drone will check its current altitude. If the drone is higher than the pre-set altitude it will start to RTH at the current altitude immediately. If it is lower than the pre-set altitude it will ascend to the pre-set altitude first before starting to RTH.
Note: The Current Altitude option is ignored in this case. The drone will always return at the pre-set altitude at a minimum.

Conclusion: The Current Altitude option setting is only taken in account in a scenario where the drone's distance to the recorded home point is in the 3m to 20m bracket. In all other cases the Current Altitude option setting is disregarded. It is perfectly safe to enable the Current Altitude option to avoid immediate landing in case of an RTH event in the 3m to 20m range. If the drone is further out it always returns at the pre-set altitude at a minimum.

Hello Jaw, thx for the great explanation for the RTH function. I’m a bit new at this, but have experienced frightful RTH results which if I didn’t force the drone via manual stick action, the drone would have ascended into tree branches above, or have crashed going forward into a nearby tree. In these instances, I cancelled RTH. I’m guessing I need to find a large field without trees or other obstacles to really see how the RTH function works. I have the RTH height set at 60 feet. Should this be lower? My reluctance to use RTH has prompted me to simply hit the land button when I want to bring my bird down. Any advice you can provide is appreciated.

 

[JAW]

Hello Jaw, thx for the great explanation for the RTH function. I’m a bit new at this, but have experienced frightful RTH results which if I didn’t force the drone via manual stick action, the drone would have ascended into tree branches above, or have crashed going forward into a nearby tree. In these instances, I cancelled RTH. I’m guessing I need to find a large field without trees or other obstacles to really see how the RTH function works. I have the RTH height set at 60 feet. Should this be lower? My reluctance to use RTH has prompted me to simply hit the land button when I want to bring my bird down. Any advice you can provide is appreciated.

I'm certainly not an expert or for that matter even "knowledgeable" in all ways Mavic. That said, I would point you to the few pages in the Mavic 2 user manual for a good explanation of RTH to include its obstacle avoidance features. You'll find that it likely will avoid a solid structure but may not 'see' the leafy branches of a tree. As far as RTH height, I use 90 feet which is about 20 feet higher than the tallest feature--tree, power line, building, etc.--- in the area I'm flying.
HTH

 

[msinger]

I have the RTH height set at 60 feet. Should this be lower?

I always set my RTH Altitude to at least 50 feet higher than the tallest obstacle I think I'll encounter during my flight. I add in some room for error since I don't know the exact height of the tallest obstacle and the drone's current altitude is only an estimate. And I of course change that setting when flying in a different location. Whatever you do, don't blindly copy the setting that someone else on this forum is using.

FYI, the RTH Altitude is the height over top of the takeoff point. So, if you're flying over unlevel terrain and the tallest obstacle is on a hill, you'll also need to account for the height of the hill.