Hi I would like to know if there is a way to view the drones corrected realtime height above sea level (in NGVD88 for example) and/or if there is a way to view it in the metadata of a picture taken in regular camera mode. I need to take photos at a certain elevation above sea level and I would like to be able to know my rtk height while flying. Also I know that the drone reads wgs84, but when connected to custom network rtk I believe that in the USA the corrections are given in nad83(2011) will this cause an issue?

I think you could do it if you knew the MSL of the drone at point on the ground. The aircraft height is reported as an altitude above the geoid when on the ground. For example my local altitude was about 95 meters but the MSL elevation was about 410. If you go to the RTK page you'll see the position of both the drone and the base including altitude. If you raise the drone up you'll see that altitude change by the amount you moved it. Therefore while flying you can look at the altitude readout at the bottom of the screen and do the difference. The captured exif altitude could also be used to calculate the difference after the fact by knowing both values.

I tried this, I shot the ground and i got 4ft orthometrical height with network rover and then used the altitude and it was way off. I don't know why but it when my altitude said 10 ft I was not at 14ft orthometric height.

jimmythejimjim Posted at 1-17 19:50
I tried this, I shot the ground and i got 4ft orthometrical height with network rover and then used the altitude and it was way off. I don't know why but it when my altitude said 10 ft I was not at 14ft orthometric height.

Unless there is a change in the RTK version, the normal aircraft uses a barometric alitimeter, and it is not particularly accurate. But DJI did place the GPS height in the EXIF data for each photo, however as I recall, not in the expected place.

jimmythejimjim Posted at 1-17 19:50
I tried this, I shot the ground and i got 4ft orthometrical height with network rover  and then used the altitude and it was way off. I don't know why but it when my altitude said 10 ft I was not at 14ft orthometric height. router ip address

I tried, the numbers weren't real

The P4 RTK is recording WGS84 ellipsoid heights for the Z value of each photo.  I'm guessing/assuming it still uses the altimeter to determine the height AGL.  You are not going to be able to see a real time orthometric height like NAVD88 because the drone has no knowledge of the geoid model (Geoid12B).  You can view the real time ellipsoid height however.  You will need to shoot your point on the ground, so for example you said 4 ft NAVD, your data collector will be able to show you the WGS84 ellipsoid height for that point.  Then place the drone over that spot.  I believe the antenna phase center height of the P4 RTK has been reported on this forum or another as 19.2 cm but I have not seen that officially documented anywhere (maybe someone can chime in).  You could just compare the ellipsoid heights by subtracting 19.2 cm (0.63 ift) from your reported ellipsoid height from the drone as it sits over the known point.    From your known ortho height and ellipsoid height you can then calculate your geoid height and then add that to the ellipsoid height to get the ortho height but again as long as the ellipsoid heights match up, you don't really need to go the extra step of calculating the geoid height.

And now that I think about it, that antenna phase center height could be measured to the camera and not the base of the drone.  DJI really should report these values if they haven't already but they did not provide the antenna height values for the D-RTK 2 base station either.  Well they did print the antenna phase center measurements to the base of the antenna mount but not for the entire rod which would have been helpful.

There is no NGVD88. It's NAVD88. (There is a NGVD29). NAVD88 does not have a consistent relationship to sea level.

CoastalCapt nailed the rest of it in post #6.