Yet another RTH question....

JY-tek · Jul 22, 2018

Pretty simple question, but I can't find a definitive answer. I have seen conflicting written information about how the drone returns to home. Does the drone follow the flight path in reverse, or does it use straight line flight to home?? I live in a very mountainous area and if it uses "shortest path" method, then I need to consider that when I'm flying around these mountains. Thanks.

msinger · Jul 22, 2018

When RTH is initiated, the Mavic will ascend to the set RTH altitude and then fly directly back to the home point. That's why it's important to set a proper RTH altitude prior to each flight.

Former Member · Jul 22, 2018

If there's conflicting information, you can always consult the current owners manual. RTH starts on page 13.

In my experience, RTH climbs to the preset altitude and makes a beeline home, providing there are no obstacles. There are some exceptions to this rule.

https://dl.djicdn.com/downloads/mavic/20171219/Mavic Pro User Manual V2.0.pdf

Ripper7620 · Jul 22, 2018

JY-tek said:
Pretty simple question, but I can't find a definitive answer. I have seen conflicting written information about how the drone returns to home. Does the drone follow the flight path in reverse, or does it use straight line flight to home?? I live in a very mountainous area and if it uses "shortest path" method, then I need to consider that when I'm flying around these mountains. Thanks.

I've flown in the mountains of Montana, and indeed, you so need to set the RTH altitude appropriately to avoid running into the mountain, because after it ascends to the preset RTH altitude, it does in fact, fly in a straight line. I'll post an example of my failure to follow this approach. here's an example of myself not setting the proper RTH altitude:

JY-tek · Jul 22, 2018

What a great video! Glad to see the drone sense the tree and go up and over! That's exactly my kind of problem. When the drone gets too far around these mountains, it looses connection and starts RTH. I've only been caught once, so far, but that's enough to cause pure panic.

If I set RTH height high enough to miss every mountain in the area, it would have to be at full max! Not sure how to handle that.

Former Member · Jul 22, 2018

JY-tek said:
Not sure how to handle that.

FPV with extreme caution.

Ripper7620 · Jul 22, 2018

JY-tek said:
What a great video! Glad to see the drone sense the tree and go up and over! That's exactly my kind of problem. When the drone gets too far around these mountains, it looses connection and starts RTH. I've only been caught once, so far, but that's enough to cause pure panic.

If I set RTH height high enough to miss every mountain in the area, it would have to be at full max! Not sure how to handle that.

I actually had go in and reset the RTH altitude to get it to fly up and over the tree line mid flight before I could ascend.

JY-tek · Jul 22, 2018

I was under the impression that the drone would sense the obstacle, then go up and over, and return to home at the new height, even if my RTH height is set lower than the new height. Am I understanding this wrong?? For instance, if I loose connection because of the mountain, I would not be able to manually make the drone do anything.

Ripper7620 · Jul 22, 2018

JY-tek said:
I was under the impression that the drone would sense the obstacle, then go up and over, and return to home at the new height, even if my RTH height is set lower than the new height. Am I understanding this wrong?? For instance, if I loose connection because of the mountain, I would not be able to manually make the drone do anything.

No, the AC won't go any higher than the max altitude set for it, and if I wouldn't have manually adjusted my RTH and max altitude, the AC would have hovered in place until the battery died. If your max altitude is set appropriately, and the sensors are set to avoid obstacles on the RTH, then yes, they should go up and over, or around on the RTH.

netfolks2000 · Jul 22, 2018

Of all obstacles, besides a power line, tree branches are the hardest for obstacle avoidance to detect, especially in lower light situations. When the drone leaves your launch point it is measuring height from that point. If you fly into a lower valley or higher mountain it is still measuring the height from where it launched. That is why it is so important for you to either keep it in sight or set that RTH height to avoid hitting any tree or mountainside. If you are in a VERY high altitude you may encounter other problems related to the thinness of the air. (By the way it's "lose" not "loose.")

JY-tek · Jul 22, 2018

So, I have mountains all around me, so I have to set the RHT altitude higher than the highest mountain? That would mean setting it to 1000 feet or so. Then any time the RTH is activated, the drone will automatically go to 1000 feet, then fly home. Seems pretty high short flights. I guess the best solution would be to set the RTH for every flight, just to make sure I'm covered without being excessive.

JDawg · Jul 22, 2018

" 1. "Smart RTH" flies directly to the Home Point based on preset altitude. 2. Failsafe RTH returns to Home Point flying back along flight route (FS RTH Overrides "Smart RTH"). 3. Low Battery RTH flies directly back to Home Point (Overrides FS RTH & Smart RTH). 4. Critical Battery Warning (Activates immediate landing.) Overrides all of the above. Seems to be the same for all the DJI Drones."

Ripper7620 · Jul 22, 2018

JDawg said:
" 1. "Smart RTH" flies directly to the Home Point based on preset altitude. 2. Failsafe RTH returns to Home Point flying back along flight route (FS RTH Overrides "Smart RTH"). 3. Low Battery RTH flies directly back to Home Point (Overrides FS RTH & Smart RTH). 4. Critical Battery Warning (Activates immediate landing.) Overrides all of the above. Seems to be the same for all the DJI Drones.

Thank you for the clarification, very useful information to know.

msinger · Jul 22, 2018

JDawg said:
2. Failsafe RTH returns to Home Point flying back along flight route (FS RTH Overrides "Smart RTH")

That's from the Mavic Air manual, right?

JY-tek · Jul 22, 2018

Great information! So, based on that information. If I have flown around a mountain, then loose connection (instigating Failsafe RTH), then the drone will simply fly back home using the same flight path to get where it is?? That would really make good sense, and save me from running into mountains.

JY-tek · Jul 22, 2018

Ripper7620 said:
I've flown in the mountains of Montana, and indeed, you so need to set the RTH altitude appropriately to avoid running into the mountain, because after it ascends to the preset RTH altitude, it does in fact, fly in a straight line. I'll post an example of my failure to follow this approach. here's an example of myself not setting the proper RTH altitude:

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In this video, did your drone RTH because of battery, or loss of signal??

JDawg · Jul 22, 2018

msinger said:
That's from the Mavic Air manual, right?

I believe that is regarding the Air. It was copied from a conversation about the Air on a different site. I hope I am not spreading bad info?

Edit: There was actually a picture of the Failsafe RTH so I think this is right, I will see if I can find it.

Ripper7620 · Jul 22, 2018

JY-tek said:
In this video, did your drone RTH because of battery, or loss of signal??

I instigated RTH to because I lost video feed, completely forgetting that I failed to reset both the max altitude and the RTH altitude. I should have lost my drone for my negligence, but just got stupid lucky.

JDawg · Jul 22, 2018

How to use DJI’s Return to Home (RTH) Safely - DJI Guides

I am new at this so I am probably missing something but in this video the Failsafe RTH was initiated but it seems the drone climbed to what is probably his RTH height before zigzagging back, so the same route but higher.

Ripper7620 · Jul 22, 2018

JDawg said:
How to use DJI’s Return to Home (RTH) Safely - DJI Guides

I am new at this so I am probably missing something but in this video the Failsafe RTH was initiated but it seems the drone climbed to what is probably his RTH height before zigzagging back, so the same route but higher.

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I believe this is what JDawg's post #12 addresses.