Forward intersection is a geodetic method for determining the coordinates of an unknown point (To) by measuring angles from two known points (Ta and Tb).
Note: For universal use we define N = North, E = East.
Formulas used:
ΔNₐ = [(Eb - Ea) - (Nb - Na) * tan φb] / (tan φa - tan φb)
ΔNᵦ = [(Eb - Ea) - (Nb - Na) * tan φa] / (tan φa - tan φb)
ΔEₐ = ΔNₐ * tan φa ; ΔEᵦ = ΔNᵦ * tan φb
N₀ = Na + ΔNₐ = Nb + ΔNᵦ
E₀ = Ea + ΔEₐ = Eb + ΔEᵦ