基于协方差的车辆检测,用协方差矩阵为描述子，检测图片中的汽车或者卡车-Covariance matrix Vehicle detection

W(n) represents the weight vector at n, W(n+1) represent weight vector at n+1. U represents the step size which control the convergence speed. The value for the gradient vector is calculated through covariance matrix R and cross-correlation r.