M4T Incorrect altitude in photo properties

[Flightworks]

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]

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.