How to use GPS/INS Offset settings

[DayGeckoArt]

I've searched and read the manual and I can't find anything clear. My DJI Air 2S drone usually has wildly inaccurate elevation data, possibly because of the datum it's using. Usually it's about 75 meters below where it should be. For example when I take a photo at ground level at 5 meters elevation, the value in the exif data is -70 meters.

How do I adjust this in Camera Calibration? According the manual it seems like I would put in -75 but that seems backward. Should I put in +75 to add 75 to the exif value?

[Paulo]

Hi DayGeckoArt,

DJI drones are known to have very inaccurate elevation (taken from barometer). To fix this Z offset, you use following script https://github.com/agisoft-llc/metashape-scripts/blob/master/src/add_altitude_to_reference.py

Hope this helps,

[DayGeckoArt]

Hi DayGeckoArt,

DJI drones are known to have very inaccurate elevation (taken from barometer). To fix this Z offset, you use following script https://github.com/agisoft-llc/metashape-scripts/blob/master/src/add_altitude_to_reference.py

Hope this helps,

Thanks, this is simple because it spells out what is being done, the value you put in is added.

But is there a reason not to use the camera calibration dialogue to change heights?

[Paulo]

Yes,

in the case of a known fixed offset from camera  center to GNSS antenna like for example the Phantom4, the measured offset in Z is 17 cm and can be input in camera calibration if your airborne GNSS positions refer to antenna.

In case of varying barometric altitudes from DJI, this offset is variable and so using a fixed off set would not be appropriate...

Hope this makes sense!

[DayGeckoArt]

Yes,

in the case of a known fixed offset from camera  center to GNSS antenna like for example the Phantom4, the measured offset in Z is 17 cm and can be input in camera calibration if your airborne GNSS positions refer to antenna.

In case of varying barometric altitudes from DJI, this offset is variable and so using a fixed off set would not be appropriate...

Hope this makes sense!

But it's not variable, or it's only slightly variable. My thinking is that the offset at least reduces the error introduced by the massive offset in the EXIF data

From testing it seems like I was right. When I have metadata values low by 60 meters, I have to put in +60 meters in that field