# Bilinear Interpolation (BI) Algorithm

Four gain values are determined in the horizontal and vertical patterns depending on the two angles $\vartheta$ and $\phi$ .

The gain values are weighted with their angle distances:
(1) $G\left(\phi ,\vartheta \right)=\frac{|\phi |\cdot {G}_{v}\left(2\pi -\vartheta \right)+\left(\pi -|\phi |\right)\cdot {G}_{V}\left(\vartheta \right)+\vartheta \cdot {G}_{H}\left(\phi \right)+\left(\frac{\pi }{2}-\vartheta \right)\cdot {G}_{V}\left(0\right)}{|\phi |+\left(\pi -|\phi |\right)+\vartheta +\left(\frac{\pi }{2}-\vartheta \right)}$