Abstract: One embodiment is a method that improves computations of correlation values between a surface roughness and terrain parameters of a terrain surface. The method includes applying the terrain parameters as an input of a Back Propagation Neural Network (BPNN) and the surface roughness as an output of the BPNN; implementing a nonlinear mapping from the input to the output of the BPNN; generating a weight matrix (?1) and a weight matrix (?2); and improving computations of the correlation values by calculating a correlation matrix by ?2×?1, calculating a unit weight which is a sum of absolute values in the correlation matrix, and dividing each value in the correlation matrix by the unit weight.