The landmarks are often used in SLAM. What are the algorithms used to extract them, and how can a robot differentiate the landmarks, if they detect one in point A at Xt and another in Xt+1? How can the robot know if it's the same landmark or not?
Landmarks or features are usually found using SURf, SIFT, or ORB. these algorithms extract corners from images and can be found in the opencv library.
Matching measured features to previously seen features is called the assignment problem. There are a couple ways to deal with this. The munkres algorithm solves this problem in O(n^4) time with a nxn cost matrix. The cost of assigning a measured feature to a previously seen feature is often the difference between the two scaled by the mahalonobis distance .