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Anafi Crash - Altitude Issue

msande

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This may be ignorance on my part, but I thought it better to share my experience.
The Anafi flew backwards into a tree during manual flight mode. I was up in the hills in southern Spain, up high. I flew manually over the valley, then turned left going through the valley when I got the WiFi warning - bring Anafi closer.
At this point I had forgotten that I had it in sport mode ( I am a newby and panicked!), so rather than going right, I brought Anafi closer by pulling back at which point it apparently hit some bushes on the mountain side some 700 feet away.
Luckily I had a screen recording, plus I kept FP6 open so I could go look for it. I finally found it around two weeks later. It was fairly steep, so not easy, plus rain etc prevented me from looking.
During the search process, I noticed that the altitude on my recording remained at 18 feet -my starting point - throughout the flight. Even when initially flying over the valley it didn't change. It also didn't warn me as I got closer to the ground prior to crashing.
This despite Parrot claiming that the Anafi uses GPS, Glonass as well as Ultrasound (Apparently that is not like sonar).

The moral of the story is check your surroundings for changing altitude when flying. This also applies the the flightplan app!
Parrot, please look at this and fix.

Thank you
 

Agustine

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Sorry to hear about your crash. You are correct about knowing your surroundings is very important.
Just wondering how the Anafi is after you found it? Will it fly again someday?
Also could you upload your flight record to someplace like google drive? In the App for your last flight it will show you the Icon for your Json file, this is your flight log and there should be one for each of your flights. If you can upload it someplace I would like to look it over.

20181125_100649_rmscr.jpg
 

Dirk_ANAFI

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If the height always shows 18 feet:
Is it possible that you flew straight horizontally into the valley and didn't really change much height until you crashed?
 

msande

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Augustine,
Thank you for your interest. I managed to save it to Google Drive, but how do i get it to you? It doesn't show up when I click attach files.
The Anafi survived, despite heavy rain and mud and being outside for a couple of weeks. It is surprisingly durable.
Mark
 

msande

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Dirk_Anafi,
That is correct. I did not manually change altitude, but flew over a much lover area, and then higher area without Anafi noticing the altitude changes.
 

Agustine

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Hi Mark
If you have uploaded it to google drive there will be a spot to get a sharable link. Just post that here or if you prefer post it in a PM to me.
 

Dirk_ANAFI

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Dirk_Anafi,
That is correct. I did not manually change altitude, but flew over a much lover area, and then higher area without Anafi noticing the altitude changes.
Mark,
then there is no fault: the displayed height is ok, always 18 feet.
Reason: the height shown in the app is the height in relation to the Anafi starting point
 

msande

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Dirk_Anafi,
I figured as much based on my experience, I just thought that I would point it out to others who might assume -like I did- that the Anafi was smart enough to sense the height.
 

Agustine

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20181021_BermejoCrashFlightRecord.json

Let me know if this works and what you find.
Yes I got it. I just ran it through FlightData Manager and yes you stayed at 18 feet until the crash. The part That bothers me is and I might be wrong but I remember the Anafi's telemetry data would show the Altitude relative to the terrain level and it is not a checkable option anymore.

Screenshot 2018-11-25 11.40.46.png
 

Dirk_ANAFI

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Dirk_Anafi,
I figured as much based on my experience, I just thought that I would point it out to others who might assume -like I did- that the Anafi was smart enough to sense the height.
The height above ground could be measured with a radar-altimeter. The Anafi only has an ultrasonic distance sensor, that can measure the height above ground up to 10m and is obviously only used for landing.
If any drone of Anafi's size displays the height above ground then this value is not measured, but derived from Google terrain data and GPS position.
 

msande

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Dirk_Anafi and Augustine,
Thank you for your insights.
I have learned a lot from this experience and from both of your replies.
 

Agustine

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I went back to one of my very first flights to see if the missing data would show up in FlightData Manager but it is still greyed out so I guess it was never a option but if you look at this video at the bottom where it shows the Alt. gauge and left of it there is a reading called Alt over ground. As the Anafi passes over the river valley you see the difference from the gauge. All the info was provided from FlightData Manager to be displayed as a over lay in the video. Wonder how it got that info?

 

Dirk_ANAFI

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...
All the info was provided from FlightData Manager to be displayed as a over lay in the video. Wonder how it got that info?

I think FDM calculates the height above ground with following data:
- GPS coordinates of the drone at takeoff = height zero of the drone
- height above NN of the drone's takeoff coordinates derived from Google or other world terrain data

During the flight the drone itself does not know it's height above ground.
But these values can be displayed after the flight from the flight data and terrain data.
 
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Agustine

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I think FDM calculates the height above ground with following data:
- GPS coordinates of the drone at takeoff = height zero of the drone
- height above NN of the drone's takeoff coordinates derived from Google or other world terrain data

During the flight the drone itself does not know it's height above ground.
But these values can be displayed after the flight from the flight data and terrain data.

You would think they could incorporate it into the App for real time read outs. Over my head and pay grade :giggle:
 
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