Thank you for the quick response JMR!:)
We actually did measure some Natural targets on the rock face With a Leica MS50, with images.
But It was very difficult to get the precise position of the target since the totalstation mesured at an angle from below, and when we flew up, the shape of our target was completly different. I did anticipate this, but this was only a first test to se what kind of result we could obtain.
I think i shuld aim for natural "corners", with three intersecting planes spread across the wall face like you suggest, similar to targetless laserscanning to get more exact center points.
My background is also from laserscanning, as i suspect yours is, and I have to say that in my opinion this is the best solution. But my customers are really keen on drone solutions, so my approach is now to scan the wall surface, fix this as the Reference for the future surveys, and do a best fit registration of the drone pointcloud or surface in a third-party software like CloudCompare or something similar.
What are youre toughts on such an approach?
Best regards
KEG