1. A method for monitoring large surface areas, said method comprising the steps of: (a) rotating a thermal camera and an electromagnetic radar about a vertical axis to scan the area to be monitored; (b) dividing the surface area to be monitored into surface elements, each of the surface elements being defined by an arcuate increment of the rotation of the camera and radar and by an increment of radial distance from the vertical axis; (c) establishing monitoring criteria for each of surface elements so defined; (d) using the radar to detect movement of objects in the surface area being monitored; (e) detecting objects differing from their surroundings by means of the thermal camera; (f) locating an object in a surface element of the surface area being monitored using the radar or thermal camera; and (g) identifying an object so located and meeting the monitoring criteria by using at least one of the electromagnetic radar and the thermal camera.