In this paper we produce first a pair of the surface orientation maps of the scene using BPS system.Then:1.segmenting the surface orientation maps into the isolated regions corresponding to the objects in the scene.2. matching the disparities between the corresponding regions.3.determining the absolute depth of 3-D surface of objects.Finally

this paper points out emphatically how to recognize and how to analyse some kinds of the main errors:（1） the measurment error of the surface orientation;（2）the reconstructed depth error

and（3）errors caused by epipolar lines being not always parallel to scan lines

and how to correct them.