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General Procedure - GPS Z vs Relative Height of Drone


We are running a DJI Phantom 4Pro and as I have found, it stores the relative altitude in the images. 

With the GCP points, we have actual NGVD88 elevations from GPS sessions.

Is there a recommended, or necessary, procedure for addressing this? Assuming you have the actual elevation of the takeoff point, you can calculate a difference, but do you then alter the elevation of your GCP or somehow alter the image altitudes?

I’ve tried the GCP alteration and it worked ok, but you then end up with vertical information that needs to be shifted to get it to a correct Z value.

Hi Graham,

DJI saves absolute altitude in the images with respect to MSL (egm96).
The workflow I recommended is described in my comment in this other post: