We where conducting a displacement for some BM (Old vs New values), we made calculations on different platforms for the North, East, Elevations. We used the NGS NCAT, Inverse 3D, TBC and manual calculations. On these methods the variations are within minutes for the azimuths. But when using the ArcMap - Toolbox - Point Distance to calculate, the differences of point to point are ok (Same on all platforms), on the contrary in the azimuth its when I see a big different up to 9°. (In azimuth from Plane (Grid) are same for all platforms.
Someone have a clue for this. Either on grid or geographic coords.
I found it interesting and curious.