$$\begin{array}{ccccccccccc}\lambda & =& S_{\lambda }x+T_{\lambda }& \text{ where }& S_{\lambda }& =& \frac{{\lambda }_{max}-{\lambda }_{min}}{N_x}& \text{ and }& T_{\lambda }& =& {\lambda }_{min}\\ \phi & =& S_{\phi }y+T_{\phi }& \text{ where }& S_{\phi }& =& \frac{{\phi }_{max}-{\phi }_{min}}{N_y}& \text{ and }& T_{\phi }& =& {\phi }_{min}\end{array}$$