Does Pix4d use or require the altitude that is embedded in the jpg images? That data is never correct from our experiences with and Inspire 1 and Phantom 4. If the altitude is incorrect then how can we believe calculations of volume or elevation grids generated from that data? We have even tried adding GCPs and they are plotting below the surface. I noticed in a DJI forum that multiple users have similar altitude problems.
Altitude in images