In the attached diagram, how will the drone RTH when battery level is too low to continue the mission?  In this mission, the drone will be flying waypoint mission out of range of controller with the continue on signal loss setting chosen.  In this particular segment of the flight, there will be no connection to the controller.  

The drone has preset RTH return option and the height is set to 249ft.

WP1 is set at 400ft height and WP2 is set at 200ft.  the drone will be flying over a 350ft hill  and then descending into the valley to continue its mission.  If the drone encounters a low battery RTH right after WP2, how will it RTH in this particular scenario?

There is an "advanced RTH" feature based on the vision system which allows obstacle avoidance while RTH.

However, I always set an altitude higher than that of the highest obstacle. The vision system is good but it doesn't see everything, trees, structure with a uniform texture...

Pay attention to the altitude reference. Calculation based on the altitude of the starting point, not based on the altitude of an object on a map expressed in AMSL.

I believe that in the user manual the RTH modes are very well described, and there is also a warning for the vision system.

Regardless, flying the drone out of range of the RC is critical. I don't know the regulations in your country, so you do as you wish.
Fly safe!

If you start your flight from the hill's upper point, the RTH will go as planned.
If you start from hill base, at the moment when arrives at WP 2 will be screwed as will be stuck on that side of hill until will make forced landing on that area.
The drone cannot make RTK by climbing more than your max AGL setting from the Home Point.
You need to set your RTH to 400 ft in this case...is measured from the initial height from Home Point....this is why if you start from top of hill, is fine, from base of hill = screwed.

Geo_Drone Posted at 4-9 22:54
If you start your flight from the hill's upper point, the RTH will go as planned.
If you start from hill base, at the moment when arrives at WP 2 will be screwed as will be stuck on that side of hill until will make forced landing on that area.
The drone cannot make RTK by climbing more than your max AGL setting from the Home Point.

Yes, home point/starting point is near the base or at least below the highest point of the hill.

I did run into a low battery scenario during an out of range waypoint mission where my Mavic 3 Pro climbed up to 1300ft to then rth to home point safely (after watching the recorded video from the flight).  But my RTH setting is set at optimal with 249ft as the RTH height.

At the time when low battery RTH was initiated, its altitude was 700-800ft.  In this situation, my homepoint/starting point was 500ft below a few 1000ft peak hills/mountains, so it was good that it did climb way up to 1300ft before bee-lining straight back to homepoint.

  I'm curious how the drone knew to go way up to 1300ft before flying back home?  If it just bee-lined RTH from the 700-800ft that it was at (which is well above the 249ft preset RTH height), it would have crashed into the 1000ft hill/mountains on the way back.  Does this have something to do with optimal RTH vs preset RTH?  If I had RTH set to preset instead of optimal, would it have stayed at the 700-800ft altitude and crashed into the 1000ft mountains?

asiangear Posted at 4-9 23:04
Yes, home point/starting point is near the base or at least below the highest point of the hill.

I did run into a low battery scenario during an out of range waypoint mission where my Mavic 3 Pro climbed up to 1300ft to then rth to home point safely (after watching the recorded video from the flight).  But my RTH setting is set at optimal with 249ft as the RTH height.

At AIR 3 you will not see this.
Optimal or Standard, will not climb more that allowed, as is considering to enter in an eventuality of Specific scenario instead of Open scenario.
So...if the hill needs to go upper than 120meters height, will not climb it, but will block as the sensors will detect an obstacle.
If you have clearance for 500meters height, will go.
Usually, should climb as the hill is climbing and you are in Open scenario as you have under 120m AGL all time, but the drone does not know this as is not having a map with heights, is using only the AGL from point of origin (Home point).
This is why I asked if you are over 120m AGL vs Home Point when need to get over the hill...as in that part if is restricted, will block, even with Optimal or Standard.
Is you are under the limit, yes, it will go and climb the hill and make RTH.
Of course, I would not recommend you to try this, I consider it a high risk scenario as you are loosing the line of sight and you are out of OPEN flight, entering in Specific one....also you risk that the drone to go into a tree, if there is thin branches, causing sensors to fail to see it and you get a crush.
One more: as the potential crush will not be recorded in your RC and GPS, as your RC will be disconnected, you will not find the drone with Find My Drone.

For this situations I have made scenarios with an Autel Evo2Pro that have independent CPU for guidance and mapping, but always I have tried to stay in highest point for take-off. Have not got any issues, but cannot compare Air 3 360 vision with 3D vision from Autel obstacle sensors that can see also branches and some wires if they are not very thin, when mapping independently...

Also if you have a low/poor contrast scene, no OA sensors will work, only laser ones.

Cheers.

Hi,

If in your drawing WP1 at 400 ft is 400 ft higher than you start point (0 height as reference) than why a RTH preset height at 249 ft ??
In general set this height above the highest obstacle for a flight.
So, set your RTH preset height higher than the hill.

cheers
JJB

JJB* Posted at 4-10 04:26
Hi,

If in your drawing WP1 at 400 ft is 400 ft higher than you start point (0 height as reference) than why a RTH preset height at 249 ft ??

My mavic 3 pro, as previously stated, did automatically climbed to 1300ft before initiating a low battery RTH and its rth height was set to 249ft.  The mavic 3 pro flew the same waypoint flight.  So I sort of wanted to see if the air 3 would react the same if it did somehow encounter a low battery RTH.

asiangear Posted at 4-10 10:16
My mavic 3 pro, as previously stated, did automatically climbed to 1300ft before initiating a low battery RTH and its rth height was set to 249ft.  The mavic 3 pro flew the same waypoint flight.  So I sort of wanted to see if the air 3 would react the same if it did somehow encounter a low battery RTH.

Hi,

really strange....if you fly higher than the RTH setting height, than with a disconnect drone remains at current height. if drone flys lower than it will climb to the RTH setting height.

So climbing to 1300 feet is....not normal.

cheer
JJB

Hi, asiangear. Thank you for reaching out. At this time, it will perform the normal low battery RTH as long as there is a GPS and GNSS signal.