M4T Incorrect altitude in photo properties

Flightworks · Sunday at 10:55 PM

I'm using the M4T to search for rare bird nests in wetlands in New Zealand. We use software that auto-searches the thermal images for heat signatures of a certain parameter, and it maps these. The altitude from the photo properties is used to position the hot spots, but the altitude is consistently 30-40m higher than the actual altitude above ground, which throws out the accuracy of the waypoints.
Drone altitude = 80m AGL
Takeoff ground level is about 2m Above Sea Level, so Drone altitude = 82m ASL
Drone photo properties altitude = 118m.
The altitude of the drone is accurate, and this can be seen in Airdata which shows 80m. So what I don't understand is why this altitude is not transferred from the flight log onto the photo properties? How can I correct the altitude in the photo properties please?
Appreciate the wisdom out there!
Thanks.

jaja6009 · 2025-10-20T01:23:42-0400

The altitude in the image is referring to the HAE or Height Above Ellipsoid.
So the 118 means that your drone was 118 meters above the WGS 80 ellipsoid.

DJI Enterprise drones that have the ability to use RTK will report two altitudes.
In the Matrice 4 Series metadata:
HAE will be in the Absolute Altitude and GPS Altitude
Relative Height or Height Above Takeoff Point will be in Relative Altitude.

What city is near where the images were taken? I can check a map layer that gives WGS ellipsoid heights for a chosen location and you can do the math.

Also since you are using the 4T, there will be some error in the given altitude since even if you were receiving corrections, the 4T does not use Time Sync to put the "survey grade" locations into the image metadata.

Flightworks · 2025-10-20T23:52:06-0400

Thanks jaja6009.
I'm about 100km, as the drone flys, from Auckland, New Zealand.
I'm not using the RTK.
What I don't understand is that the altitude in the flight logs is correct, but this is not used in the photo properties. Is the drone calculating the altitude correctly, then adding 40m for the photo properties???
Is it using HAE for photos and Relative Altitude for logs?

jaja6009 · 2025-10-21T00:16:13-0400

Your flight logs will show altitude as above the takeoff point and this in the metadata will be Relative Altitude.

Relative Altitude is in the metadata, photo properties just does not use it.

To answer your question on adding 40m, no, the drone is calculating the altitude as designed and reporting the altitude as above the WGS 84 ellipsoid.

Since these drones can be used for photogrammetry (mapping, and especially the E version) they report altitude similar to a GNSS rover (drones are aerial rovers). When you map you can have your altitudes in ellipsoid value and then easily apply a vertical datum transformation to get to an orthometric elevation based off of a geoid.

jaja6009 · 2025-10-21T00:27:44-0400

Information on DJI RTK drones and how they report their altitudes:

How to Process DJI RTK Coordinate Data in Agisoft Metashape: Complete Workflow Guide | Agisoft Metashape

Learn how to import, process, and optimize DJI RTK coordinate data in Agisoft Metashape to achieve centimeter-level accuracy for mapping and 3D modeling projects

www.agisoftmetashape.com

Mavic 3E RTK (HAE) to orthometric coordinate system

I am attempting to process imagery acquired with a DJI Mavic 3 Enterprise RTK using Drone2Map (v2023.1.1), and cannot figure out the correct combination of Image and Project vertical coordinate systems to get the DSM output in orthometric (ASL) elevation (NAVD88). I have reviewed multiple...

community.esri.com