A new quality map is introduced for wrapped phase image in this paper. In order to reduce the affluence of the slope effect in the conventional quality map and improving edge-detection ability in the steep discontinuity areas where the real phase dif- ference is 2 kπ

a quality map derived from the consistency of normal vectors is proposed. In 3×3 window of wrapped phase image

the center is selected as the reference point and then the local unwrapping is performed in the window. After local unwrapping

eight triangles are formed by the center and every pair of neighboring points on the border of the window

then the syntheti-cal normal vector formed by the eight normal vectors of the corresponding triangles is taken as the normal vector of the local unwrapped surface. Finally

the quality value of the center is defined by the sum of angles between the eight normal vectors and the synthetical normal vector. The tests performed on simulated data and real InSAR wrapped phase image show that the new quality map has the better guiding ability than the conventional quality map in the quality-guided phase unwrapping algorithm.