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davedoc

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I was flying an orbital around the AIG building in Houston, TX, with a Mavic Pro. Mostly because I thought it would be a really cool shot. Before take-off I set the RTH altitude to be 392 feet. I knew that the height of this building was greater than that besides I wasn't planning on losing connection. I've seen so many different crash analysis reviews on the forums that I thought I could just fly up about 75 feet more when I got to the back side of the building. Yeah, that extra altitude thing didn't happen. I went from near 100% signal to zip, zero, nada in no time flat while flying. I lost connection for about 30 seconds and all I could think of was that my drone crashed into opposite side of the building trying to RTH when it lost signal. When I finally got signal back I didn't even see the building and knew I was safe. Phew!

Ok, fast forward to downloading and viewing exactly what happened. I feel sick seeing just how close my drone came to being in pieces or stuck on the top of the building, or both. There were a couple of antennae that may not have been seen by the obstacle avoidance and could have been the downfall of my drone. I've posted a short clip of what the drone did right after it lost connection and initiated RTH as it should have.


For learning purposes, both mine and the readers, I've posted my log from this flight
Flight log

Finally, the knowledge that I would like to gain from this is does the RTH altitude stay the same if I'm already above what the max RTH is set to? The drone goes up a few feet on its own. Is that the obstacle avoidance seeing the top of the building? Right when it got to the top of the building it stopped because it sensed something. Was that the building itself or the small antennae that it somehow detected...thankfully?
 
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does the RTH altitude stay the same if I'm already above what the max RTH is set to?
The drone goes up a few feet on its own. Is that the obstacle avoidance seeing the top of the building? Right when it got to the top of the building it stopped because it sensed something. Was that the building itself or the small antennae that it somehow detected
If the drone is at or above the set RTH height, the drone will come home at the height it is already at.
You were flying at >600 ft with an RTH height set to 400 ft.
It appears that OA stopped for the antennas.
 
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Interesting issue- wonder if it was the building, all the radio interference emanating from all the wireless network traffic inside the building, or a combination of both? Not a flight I would have done, but a really good learning experience for all. Glad it wasn’t an accident for you. Thanks for posting it.
 
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If the drone is at or above the set RTH height, the drone will come home at the height it is already at.
You were flying at >600 ft with an RTH height set to 400 ft.
It appears that OA stopped for the antennas.

I wondered about that as I was flying a path that put some tall power lines on the shortest route between my M2P and home. I was higher than the lines but had set RTH lower than the lines by oversight - didn't even notice them until ot was too late.
 
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Almost anything that is conductive will block the WiFi control signals green tree leaves, steel bridges, concrete buildings with rebar.
 
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If the drone is at or above the set RTH height, the drone will come home at the height it is already at.
You were flying at >600 ft with an RTH height set to 400 ft.
It appears that OA stopped for the antennas.

It looks to me as though it was the water vapor from the cooling towers that stopped the drone. It stopped when it was thick and obscuring the picture slightly then proceeded when it thinned out.
 
It looks to me as though it was the water vapor from the cooling towers that stopped the drone. It stopped when it was thick and obscuring the picture slightly then proceeded when it thinned out.
That's kind of what I was thinking may have happened instead. There was no noticeable movement left if it had detected the antennae. My understanding of the forward sensors though is that they are ultrasonic which would have not seen the vapor.
 
RTH OA will try to go over obstacles, but in this case with the fog, it didn't see a way over. That or it pauses first to think about it, but the obstacle disappeared before it would react. Also RTH OA will not go higher than max height.

I'm surprised it didn't backtrack the last 60 seconds of travel when signal was lost.

A good rule of thumb I use to check height clearance: If in your view your potential obstacle height is below the horizon, you'll clear it. I can't remember but I think that works even when the gimbal is not straight out.
 
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Does anyone know what the algorithm is in this scenario? Backtrack? Move left or right? Gain elevation? If the front sensors are ultrasonic then cooling tower output should not have stopped the drone.

I don't know why it's so important. Especially since I got my drone back. Maybe I'm just curious about what it did. I thought that the logs would show sensor data but I don't see that anywhere in the logs I posted.
 
The Mavic Pro doesn’t backtrack, it just attempts to climb above the blocking object. The forward object avoidance sensors are optical, not ultrasonic.
 
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My understanding of the forward sensors though is that they are ultrasonic which would have not seen the vapor.
Only the downward sensors are ultrasonic.
The forward sensors are optical.
 
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