Mavic 3 waypoint missions

General Discussion
21

I just thought of something else.

Your waypoint 6 appears to be inline with the two waypoints on either side. If Litchi is using a curve size of 0 (zero) for waypoint 6, that will cause the WPML data to use a straight line at that waypoint. That is not a WPML error but I don’t think that DJI Fly provides an option for straight lines so it is unclear how the DJI Fly would handle that case. I can see from your DJI Fly snapshot that from waypoint 6 onwards, the mission uses straight lines (and is weird).

Please try setting the curve size at waypoint 6 to a non-zero value in Litchi’s Mission Hub. Then use my utility to convert the mission and load the KMZ file into DJI Fly. Let me know if this work. If it does, I’ll remove the straight line option from any converted mission.

22

Hello,

What do you mean by WPM

Screenshot_20230714-122507
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L data?

I modified wpt 6 (non zero value)and the result is good now, see attached screenshot

The fact remains though that there are different heights. See the previously attached table . Can you explain this?

Furthermore, the whole procedue to convert the litchi flight to the dji fly app unfortunately remains very cumbersome.

23

Excellent. Thanks for that. I’ll make a change to my application to prevent straight lines when using a Mavic 3.

I have noticed that the results from Google’s Elevation API are a little different from what I see in Litchi. Send me your Litchi CSV file and I’ll manually do an API call and post the results. You may have to send me a private message to attach a file.

24

How do I send a private message?

25

Click on my name or icon then click on “Message”.

26

I cannot upload csv files

27

Go to my web site and email me. You can also copy and paste the csv data into the email to me.

28

I did send a private message en pasted the content of csv files. I hope that it was succesfull

29

WPML is the language DJI uses to store waypoint missions.

https://developer.dji.com/doc/cloud-api-tutorial/en/feature-set/dji-wpml/overview.html

Yes, I received the CSV data. I have tried a couple different ways to query the elevation data using Google’s Elevation API. Both ways have returned the same values. These values yield slightly different results from what is shown in the Mission Hub. However, these values do match what I see in Google Earth Pro.

This will require more investigation.

30

Thanks for the quick responses and good luck with your further investigation

You say : ‘‘These values yield slightly different results from what is shown in the Mission Hub’’
I would like to point out that in the Lank.csv flight, however, the differences are much greater

What method does litchi in the Mission Hub use for determining height?

31

That is a good question and I do not know the answer. However, based on what I am seeing, I do not think it is using the Google Elevation API.

Have a look at this. You can repeat this yourself to verify:

  1. Litchi shows that WP2 is 8 meters higher (48-40) than WP1. See this snapshot of your mission:

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  2. Using Virtual Litchi Mission, I exported your mission to Google Earth Pro. Notice that WP1 in Google Earth Pro is at 70 meters MSL:

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  3. Google Earth Pro shows WP2 at 87 meters which is 17 meters higher than WP1:

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My calculations that I use in my mission converter match what I see in Google Earth Pro. I can only conclude that Litchi is using a different elevation model from Google’s, but I don’t know what elevation model that is.

32

This is part of the VLM thread where the difference between Litchi’s and Google’s elevation is mentioned:

33

OziExplorer uses NASA’s Shuttle Radar Topography Mission (SRTM). I found in OziExplorere the following SRTM values for the five waypoints:
wpt 1 28 m
wpt 2 37 m , so + 9
wpt 3 40 m , so +12
wpt4 36 m, so +8
wpt 5 27 m, so +1
The looks very similar to the values used by Litchi.
The accuracy of the data is not high; the maximum deviation in altitude is about 8 meters. The NASA data has certain drawbacks: there is no data north of 60° N or south of 60° S, and there are gaps in the data for some mountain and desert areas.