Hi there,
Does anybody know which geoide model the DJI RTK is using?

Hi, Spipp. Thank you for reaching out. The RTK function is switched on and by default, the WGS 84 coordinate system and ellipsoidal height are used. Hope this helps.

DJI Gamora Posted at 7-3 03:21
Hi, Spipp. Thank you for reaching out. The RTK function is switched on and by default, the WGS 84 coordinate system and ellipsoidal height are used. Hope this helps.

Dear DJI Gamora,

Feel free to put a warning as your colleagues have already done, but I repeat my words, do not feel personally offended.

First of all, thank you for taking the time to take an interest in our questions, but you do not have the required skills. The OP's question expects an answer like: EGM96.

This is not a personal attack, it is an observation. The admin/moderator group of this forum obviously has no survey experience. Again, it is not an insult, feel free to ask if you need in depth explanation of what is the difference between geoid and ellipsoid for example.

I think the answer to this question is EGM96 because it is the geoid that is mainly used to do the HAE to AMSL conversion. But there are others.

I reformulate the question for your engineers because the answer could be very interesting and helpful:

Which calculation leads to the resolution of the altitude ASL indicated on the screen of the RC ? :



Thank you

LV_Forestry Posted at 7-3 09:28
Dear DJI Gamora,

Feel free to put a warning as your colleagues have already done, but I repeat my words, do not feel personally offended.

Hi, LV_Forestry. If the RTK function of the drone is enabled, the data obtained by the aircraft is the WGS84 coordinate system and ellipsoid height, and this information is also displayed on the RTK setting interface. However, if you are looking at the ASL height of the app interface, this is indeed the EGM96 height, as the app converts the ellipsoid height to the EGM96 height.

As for your question about how to calculate the ASL height resolution displayed on the RC remote control, can you please provide more details so that we can further check? Thank you.

DJI Gamora Posted at 7-8 19:31
Hi, LV_Forestry. If the RTK function of the drone is enabled, the data obtained by the aircraft is the WGS84 coordinate system and ellipsoid height, and this information is also displayed on the RTK setting interface. However, if you are looking at the ASL height of the app interface, this is indeed the EGM96 height, as the app converts the ellipsoid height to the EGM96 height.

As for your question about how to calculate the ASL height resolution displayed on the RC remote control, can you please provide more details so that we can further check? Thank you.

Hi DJI Gamora,

Thank you for this confirmation. EGM96 is the geoid usualy integrated in GNSS receivers.

There is no need for more details, you have answered the question sufficiently.
I know that these are not very obvious concepts for people who do not use them. Also above you will find an illustration,

-The green line is the zero level of the ellipsoid height. If you take a photo with a DJI drone (RTK or not) on this line the altitude contained in the EXIF will be zero meters.
This line represents an imprecise average of the curvature of the earth, a theoretical sea level which facilitates calculations. The altitude included in the EXIF of DJI drones is noted "h" on the illustration below and called "HAE" Height Above Ellipsoid.

-The Red line is the Geoid. It is the mean sea level (MSL) which takes into account the real curvature of the earth which has more the shape of a potato (random shape) rather than a perfect sphere. There are very many geoids, each country has one, or even several for countries with a large area.
To make things easier, the geoid EGM 96 was created. Earth Geoid Model 1996. It is not a high precision model but sufficient for applications such as the indication of altitude "ASL" Above Sea Level for drones.
It's a raster map with squares inside (I'm simplifying), each square has a value. This value is the difference between the ellipsoid and the geoid at a given location. It is marked "N" on the illustration.

-The Orthometric Height "H" is actually the ASL, It is the result of the operation H (ASL) = h (ellipsoidal height) - N (Geoid Height from EGM96)

DJI Gamora Posted at 7-3 03:21
Hi, Spipp. Thank you for reaching out. The RTK function is switched on and by default, the WGS 84 coordinate system and ellipsoidal height are used. Hope this helps.

Thanks, it was a precise and proper answer!

djiuser_WNEDX07zAswO Posted at 12-1 02:42
Thanks, it was a precise and proper answer!

You're most welcome. Please feel free to reach us anytime!

LV_Forestry Posted at 2023-7-9 02:09
Hi DJI Gamora,

Thank you for this confirmation. EGM96 is the geoid usualy integrated in GNSS receivers.

Excellent Answer! Thank you.