How to calculate volume of a pile if an object is above image?

I am wondering what the best practice procedure is to calculate the volume of a pile of material if an object is in the way. For example, imagine a pile of pebbles in a quarry with a machine arm over the top of the cone shaped pile. How would you work with this to get the best data to calculate the volume of the pile?

Without the arm, you draw lines around the pile and then DroneDeploy uses elevation data to calculate the volume. But, since the arm is in the way and much higher than the pile, I imagine it would throw the data off. Any ideas as to how to handle this?

See image as example.image

Manually capture photos from a lower altitude showing the separation pictures from both sides help to have it stitch properly. Ideally upload these photos along with the mission photos and cross your fingers. I’ve had it work on some maps but not all.
Lastly you can do a volume calculation of the pile drawing around the conveyor and then subtract that volume from your total pile volume.