System for monitoring a piece of land, comprising a monitoring station and at least one monitoring sensor placed at a high point so as to cover said piece of land, said at least one monitoring sensor comprising means for delivering, to the monitoring station, real-time images of the piece of land, the monitoring station comprising means for analysing successive images received from said at least one monitoring sensor by searching for differences between said successive images so as to detect movements representative of an intrusion onto the piece of land, characterized in that the system for monitoring the piece of land furthermore comprises at least one dissuasive vehicle connected by a wireless link to the monitoring station; and in that the monitoring station comprises: - means for obtaining a reference map representative of the geometry of the piece of land; - means for, when the monitoring station detects a movement representative of an intrusion onto the piece of land in the images received from said at least one monitoring sensor, finding, in said images, georeferenced landmarks of the piece of land and determining an intrusion position on the piece of land from said images and from the positions of said georeferenced landmarks on the reference map; - means for transmitting to at least one said dissuasive vehicle information representative of the determined intrusion position and instructions to move said dissuasive vehicle to the determined intrusion position; and in that each dissuasive vehicle comprises: - means for obtaining the reference map; - means for receiving, from the monitoring station, the information representative of the intrusion position and the instructions to move to the intrusion position; - means for determining a path to follow, from the reference map, so as to move said dissuasive vehicle to the intrusion position; - means for automatically following the determined path; and - means (804, 805) for detecting unexpected obstacles during the movement of said vehicle over the piece of land and for adapting the determined path, in order to circumvent the detected unexpected obstacles. - means for obtaining a reference map representative of the geometry of the piece of land; - means for, when the monitoring station detects a movement representative of an intrusion onto the piece of land in the images received from said at least one monitoring sensor, finding, in said images, georeferenced landmarks of the piece of land and determining an intrusion position on the piece of land from said images and from the positions of said georeferenced landmarks on the reference map; - means for transmitting to at least one said dissuasive vehicle information representative of the determined intrusion position and instructions to move said dissuasive vehicle to the determined intrusion position; - means for obtaining the reference map; - means for receiving, from the monitoring station, the information representative of the intrusion position and the instructions to move to the intrusion position; - means for determining a path to follow, from the reference map, so as to move said dissuasive vehicle to the intrusion position; - means for automatically following the determined path; and - means (804, 805) for detecting unexpected obstacles during the movement of said vehicle over the piece of land and for adapting the determined path, in order to circumvent the detected unexpected obstacles.