I see a lot of triangulation solutions like this one : Q: Trigonometry Bearings: Find distance between 2 points based on separate bearings
What I can't find is a triangulation not for a flat surface. My example : Two people on two hills (known coordinates) with Theodolites, are pointing the same building on the fields (600m from the first hill and 800m from the second hill, elevation differences) in front of them. They get the azymuths and angle pointing the building from their location.
My question now : is this angle because of the difference on elevation from the observed building, make any difference on the calculation? And if yes, how can they calculate the coordinates of the building?