Litchi autonomous flight: lost my bird

[skyeboysteve]

Thanks for sharing the results, diveguy.

One thing to keep in mind is google earth terrain mesh resolution is relatively low. Usually only one elevation point per 100'x100' area, except for areas of interest. Outside the USA, you'd be lucky to find mesh more accurate than 300'x300'. This doesn't matter so much in flat areas but in rugged terrain it can make elevation data nearly useless. Have you noticed that hills and mountains with steep slopes often appear lower in height on google earth than they actually are in real life?

Another thing to keep in mind is how fast you're making your drone fly vs how much altitude change you need. The maximum vertical speed of the phantom 3 seems to be just under 1,000 feet per minute near sea level and normal operating temperatures. So if you're cruising at 35mph, your best angle of climb is 18 degrees--probably smaller angle when at higher colder altitudes in the mountains, though you may not reach 35mph either depending on any tail winds that may help keep maximum speed.

I know it defeats the advantage of mission planning offline, but I never fly a waypoint mission in an area that I haven't scouted out first with the P3, taking note of altitudes first hand via the go app. By comparing obstacles with the horizon you can tell if you're higher than the obstacle or not. Of course if you're surrounded by mountains that's impossible. Another method is to fly towards the obstacle and see if the top of it appears to go lower on your screen as you approach--if so you're going to clear it). If any point on your screen appears stationary relative to your screen, it means you're on a collision course.


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[Sagebrush]

Thanks for sharing. I've got a Litchi mission planned around some cliff's that's got me spooked.

When you said you use Google Maps to check the elevation during flight planning, do you mean Google Earth? That's what I use–I don't see elevation in the Maps version. (This distance calculator looks interesting. Wish it could be set in feet instead of meters.)

Perhaps you thought of this, but in the future, if you're planning a night-flight Litchi mission in the mountains, you might consider running it (slowly) during the day first, so you can watch your screen for oncoming obstructions with your finger on the ATTI mode button. But having typed that... I think you were doomed to lose connectivity because of terrain. (That's what I think anyway.) Thoughts?

I have not tested Litchi by switching to ATTI during the mission to see how fast the transition takes place. Anyone?

Again, thanks for posting and I hope your bird is okay.

S

p.s. Back in my stick and rudder days, I never flew in the mountains at night. Scared the crap out of me. There's no depth of vision in the black timber.

 

[Ed209]

Good follow-up on the cause of the problem. Glad you got it back. What are you using to convert the DAT file into something healthydrones can use? I've got a bunch of missions out of r/c range that are inaccurate because the sync from Litchi is only when the r/c was in range. I asked about this before and there didn't seem to be a solution yet.
Thanks

 

[diveguy]

Thanks everyone. I'm consolidating my responses from some previous questions to help keep things tidy:

"I thought I was ambitious with my first flight, but not compared to this! Had you posted your thoughts on this mission prior to flying, I and many would have advised against it. It's the worst choice you can try, no matter how carefully you plan. Luckily it didn't hit anyone, to boot."

This wasn't my first flight - I've done several at a local park and wetlands area first. I intentionally flew over a hiking trail, at night, and there was nobody in the area (there is rarely anyone on it in the day, even on weekends). Ambitious? Perhaps, due to the altitude, but not the course. It was a very safe area to fly and the reason I flew near the trail was so I could have a good chance of recovering it if lost here.

"So now that you know what mistake you made, what will you do differently on future Litchi missions? I know you said you will set your waypoints higher, but what else? What else can us as a community learn from this?"

I would actually like to repeat this flight, but first I will walk the trail with my handheld GPS and manually measure the elevation. I won't trust Google Maps for precise altitudes (within 200 feet) when flying over bumpy terrain. I'm going to continue to practice with Litchi in very controlled areas for another 10 flights or so until I feel extremely confident in it.

"When you said you use Google Maps to check the elevation during flight planning, do you mean Google Earth? That's what I use–I don't see elevation in the Maps version. (This distance calculator looks interesting. Wish it could be set in feet instead of meters.)"

You can find elevations on Google Maps by right-clicking (option-click on a Mac) on the map. It will pop up a box that shows the GPS coordinates for that area. Copy those coordinates and go to Google Maps Find Altitude and paste in the GPS coordinates and it will show the elevation for that point.

Another helpful tool in Google Maps for drone users is to control-click (on a Mac) and click "measure distance". Then click on another part of the map and it will tell you exactly how far away it is. While helpful for mission planning, I wouldn't count on Google Maps for precise elevations anymore...

- - -
Overall it may have been a semi-ambitious mission, but only due to the elevation/altitude climb. I wasn't far (in terms of distance), it was over/near a hiking trail with no trees, away from homes, with no people on the ground. It's very scary to set your bird off on its own and I has a sphincter factor of 9.5 when it didn't come back, but that's what you have to do to gain confidence sometimes.

 

[Sagebrush]

Overall it may have been a semi-ambitious mission, but only due to the elevation/altitude climb. I wasn't far (in terms of distance), it was over/near a hiking trail with no trees, away from homes, with no people on the ground. It's very scary to set your bird off on its own and I has a sphincter factor of 9.5 when it didn't come back, but that's what you have to do to gain confidence sometimes.

Great thread, great post! Thanks again.

S

 

[sbarton]

Autopilot is supposed to trigger rth when the signal is lost, but it's broke, a bug in the sdk. Litchi is not supposed to trigger rth with signal loss, an autonomous feature in Litchi, it's supposed to continue the programmed mission. So logically the bug can't affect Litchi, and I believe Litchi has stated this.

What if you are using Litchi for FPV flying not waypoint mission?

 

[oakmeadows]

No trolling, this forum is full of poorly researched half truths as well as all the good information. You're right though, I should have read the whole thread, just as you should have done your research before posting a comment that could have put the frighteners up a lot of users!

Oohhh handbags at dawn


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[JickMagger]

You can find elevations on Google Maps by right-clicking (option-click on a Mac) on the map. It will pop up a box that shows the GPS coordinates for that area. Copy those coordinates and go to Google Maps Find Altitude and paste in the GPS coordinates and it will show the elevation for that point.

Another helpful tool in Google Maps for drone users is to control-click (on a Mac) and click "measure distance". Then click on another part of the map and it will tell you exactly how far away it is. While helpful for mission planning, I wouldn't count on Google Maps for precise elevations anymore...

Cool. If you get Google Earth Pro (it's free) you will get instant elevation display in the lower right corner as you move your mouse around the map. Also, if you draw a path between two points, you can get an elevation profile for the path; it will show you a side view of the elevation along the whole path. Very useful.

But then you still have to add the height of the tallest tree or object you think would likely be in the area, with at least a x2 or x3 margin of error. I like to fly new Litchi missions way high first, then study the video and adjust the height downwards if I want to refly it lower.

But I can easily see myself making the same mistake as you did! It is tricky to know exactly how quickly the Phantom will gain altitude between two different-altitude points. Thanks very much for posting the analysis of what happened.

 

[CptPhantomFlyAway]

I have requested a lock button but doubt it'll ever happen. A simple lock button in the app so nothing new can be registered during examining a finished mission, or whenever you want to avoid setting a waypoint or poi by mistake.

I've been setting waypoints first then poi after. As long as you don't restart the app poi stays highlighted and worse case you accidentally add an extra poi. Although I do agree a lock would be nice. Ultimately it comes down to measure 2 cut once. Gotta cycle through your wp and verify they're correct

 

[AdvRider]

I routinely fly Litchi missions with my P3A....always running the latest DJI firmware and latest iOS....about 95 successful missions so far. I do mostly mountain and coastal flying and routinely deal with varying winds, mountain elevations, and intermittent signal loss. For me, I feel much more secure knowing the bird will do its best to stay true to my selected course and will avoid flying over homes and other high risk things I programmed it to steer clear of.....especially if I happen to lose sight or signal of the UAV. I like the fact, unlike RTH which will bring the bird back in a straight line, LITCHI will come back the way I planned...i.e., not over a playground or something risky I specifically wanted to avoid. The other big advantage with relying on waypoint flying with LITCHI is that unlike a bird that has entered RTH, LITCHI will continue fly the return side of the waypoint mission at whatever speed you program, i.e., 30+ mph. RTH is good for about 22mph from what I have seen. This extra 10mph of LITCHI speed can be the difference in making headway in the wind and making it back home.

The only Litchi weirdness I have encountered was an exceptionally early loss of signal which I traced back to Litchi being locked down on channel 7. How it got locked on channel 7 is a mystery to me since I always set my apps to AUTO channel selection...and never mess with it thereafter. Could it be possible that a Litchi update flipped me to channel 7.....who knows? After that incident, I have added a line on my preflight checklist to compel me to check that "auto channel" selection is indeed "checked" in the Litchi iOS app immediately before takeoff.

I rarely us the DJI go app anymore...except for camera tweaks.

Fly Safe


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[shockwave199]

Interesting. I have much more success using channel 20 in the go app and I choose that same channel in litchi. No problems so far but I tend not to let a mission get more than 2k' from me and often much less. I don't use it for distance flights as much as I do to just to thoroughly cover an area in an interesting way, getting all the views I can. I also haven't pushed a mission past 12 minutes yet as it's winter here and I plan conservative flights accordingly.

 

[movius]

What else can us as a community learn from this?


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Not to fly autonomous missions up mountains perhaps

Nothing wrong with Litchi, people just can't omit that they do anything wrong and the software or firmware is the first thing they want to blame, you see it here over and over.

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[DarkCargo]

Lost my drone today... at the third waypoint, the Litchi app disconnected. RTH did not work, giving me a failure to connect to server cue. After a 3 hour needle in a haystack search following the track... that puppy is gone (DJI Phantom 3 Pro)... I just can't trust the Litchi software after that experience.

The Litchi software was the latest version and the DJI firmware was the latest Phantom 3 Professional Firmware v1.9.60. Total bummer... was recording a 35 acre piece of property for real estate purposes.

 

[Mark The Droner]

Sorry for your loss.

Are you sure your mission didn't crash your aircraft into trees?

 

[shockwave199]

If those waypoints are feet and not meters, you crashed into trees. Start looking around the third waypoint.

 

[DarkCargo]

Altitude in meters. After the disconnect, I could still hear the P3P flying... good controller signal throughout. Followed the track through the woods... no luck.

 

[impilot51]

But the mission should have continued through the entire planned mission, even without connection. What was the finish action parameter see to?


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[JickMagger]

Hindsight is 20/20, but if you had good controller signal you should have been able to press the RTH button on the controller.

 

[AdvRider]

I have well over 200 missions with Litchi running under iOS. Never lost a bird due to Litchi....it was my own mistake both times. First crash was an altitude programming error, ie, failing to do a thorough pre-flight review of the mission parameters. Fortunately, I was able to locate the aircraft after an extensive hike through mountainous woodlands in WNC....damage was minimal...just broken props...and my last mulligan I am certain. The second incident had nothing to do with LItchi, but had everything to do with an overly aggressive battery mod on my P3A. This put her in the Intercoastal waterway when something failed, maybe a motor controller...but definately not a Litchi issue. I also had one incident where I fat fingered an extra waypoint into my flight plan...very easy to do whilst using an iPad. I immediately recognized that my new P4 was flying away after reaching the intended last waypoint in front of my home. All it was doing was flying to that extra point in space that I had fat fingered. Flipped RC into sport mode and brought her back smartly. Gave me a startle nonetheless! Sorry for your loss.

 

[DarkCargo]

Hindsight is 20/20, but if you had good controller signal you should have been able to press the RTH button on the controller.

The red range ring and the controller displayed plenty of available signal strength... yet still the software still displayed DISCONNECT at the top of the screen. Android version of the software... Again, the RTH function gave me an ERROR cue about failure to connect to the server and did not work. Switching to P from F mode was no help either in regaining control.