1. A method for detecting incorrect associations between keypoints of a first image and keypoints of a second image, keypoints of the first image indicating characteristic features of the first image associated with keypoints of the second image indicating characteristic features of the second image, the method comprising: forming initial associations between keypoints of the first image and keypoints of the second image, wherein the initial associations comprise incorrect associations; associating every keypoint of the first image with every keypoint of the second image to obtain global associations; determining similarity measures for pairs of initial associations; determining similarity measures for pairs of global associations; determining a first number of pairs of initial associations having similarity measures within a predetermined range; determining a second number of pairs of global associations having similarity measures within the predetermined range; and comparing the first number of pairs with the second number of pairs to detect whether the initial associations corresponding to the first number of pairs comprise incorrect associations.