Far-field cameras, thermal vision, and pan/tilt/zoom cameras are used to remotely monitor border zones. Unmanned aerial vehicles (UAVs) fly continuous GPS-guided missions to give operators a bird’s eye view. Surveillance towers typically use radar as a cost-effective way to get broad sensor coverage of diverse border zone terrain. Intrusion detection systems like underground buried cables are used to monitor electromagnetic field changes to distinguish between people, vehicles and animals at a perimeter. Outdoor motion detection is also done with microwave and infrared sensors. Intelligent pressure fence sensors detect when intruders climb or cut a fence-line.