The roof edge is detected by using local extremum of maximum main curvature along the direction of maximum main curva ture, and the direction of minimum main curvature is the trend of the roof edge.

• 通过屋脊边缘沿最大主曲率方向的最大主曲率局部极值检测屋脊边缘，同时最小主曲率的方向就是屋脊边缘的走向。