This paper presents a novel framework for detecting nonflat abandoned objects by matching a reference and a target video sequences. The reference video is taken by a moving camera when there is no suspicious object in the scene. The target video is taken by a camera following the same route and may contain extra objects. The objective is to find these objects. GPS information is used to roughly align the two videos and find the corresponding frame pairs. Based upon the GPS alignment, four simple but effective ideas are proposed to achieve the objective: an intersequence geometric alignment based upon homographies, which is computed by a modified RANSAC, to find all possible suspicious areas, an intrasequence geometric alignment to remove false alarms caused by high objects, a local appearance comparison between two aligned intrasequence frames to remove false alarms in flat areas, and a temporal filtering step to confirm the existence of suspicious objects. Experiments on fifteen pairs of videos show the promise of the proposed method.