Aiming at the problem of using image registration to identify the target and measure the target rotation angle

a fast angle measurement method based on ORB is proposed. While the feature matching identifies the target

using the rotation invariance of the ORB feature

rotation angle of the matching point is obtained according to angle difference of the main direction of the matched feature points. Then

the angle data is subjected to iterative self-organizing clustering（ISODATA） analysis

the wrong angle data is eliminated

and the average value of the remaining angle data is taken as the target rotation angle. Experimental results show that the proposed method can quickly identify

locate and can measure angle on different scales

rotation and occluded target. The angle error is about 0. 3°

and the consumed time is about 0. 6 s. The measurement precision and time complexity are greatly improved compared with traditional algorithm.