I.e. you aim at a player and want to get his handle?
I would make an attempt to get approximate 2D-coordinates to see if a player object is within a circle at that point.
If you have your coordinates, your azimuth and altitude angle you can create a vector and see where it intersects the terrain mesh.
However, another solution is to shoot a projectile close to that person, and get its final coordinates. Then you create a catch circle from that place.