Hi again,
I am not familiar with DJI drones, but here is the workflow I use and/or could be useful:
1. As far I have read - the DJI's global accuacy is about 1m (in position) and about 3m in altitude - hope this is enough for you
2. I don't know how are your images geotaged - if the information is kept in the exif of your images (you may check this i.e. using Ifran View ->Image->Information and then Exif button - an additional extension may be installed). There you should see the Northing, Easting and other data from the IMU unit (Omega, Phi, Kappa - resp. Yaw, Pirch Roll). If you load such images into PhotoScan - you should see this information in the Reference pane (in the top part - where is this iformation for each image) - then you just go and compute it.
3. I have IMU unit for my Near-IR camera Tetracam - here I recieve a TXT file in which I have the LAT/LOT/Elev/Yaw/Pitch/Roll defined for each of my images - I just load this information into PS, say which field is whih and it should look like in my point 2.
4. Just for case - I don't know how large are the areas you will be working with - but this is what I would do ... I would define a local coordinate system and use it in case of emergency, when the drone data won't be working.
a) pick a point in an aera that is flat - this will be your inital point [0, 0, hanheld measured elevation as Z].
b) you shold shift the the ccoridnates i.e. to [1000, 1000, Z] so you won't fall into negative values
c) Pick another point laying in approximately the same altitude and measure the distance in-between these two points (measure it several times with a tape and make an overage) - this point will define the Y axis of your coordinate system and it's coodinates will be [0, DISTANCE, Z] - resp. [1000, 1000 + DISTANCE, Z]
d) Pick the third point - perpedincular (as much as possible) to the line defined by point 1 and 2 (from the point 1) and measure the distance again. This will have the coordinate [Distance 2, 0, Z].
e) use some kind of "Targets" that will be visible on the photos
f) use these points as markers when you will be processing the photos in PS
g) three points are the miminum for having the model "georeferenced" - it may not be well possitionally accuravy in all of the points, as only three GPCs were used (and are not equally placed) but your model will be in scale with the defined accuracy
h) check my "image" for the local coordinta system estalishment in the attachement
I hope that you will my guide a little bit usefull.
As I wrote earlier - the last method is the least accurate but can save your data. Use any axes orientation - but remember to calculate the coordinate values correctly.
Jan