The principal UGS system used by the US military is the AN/GSR-8 Remotely Monitored Battlefield Sensor System (REMBASS II), which detects, classifies and determines the direction of movement of intruding personnel and vehicles. The system uses three basic sensor transducers, including a basic seismic/acoustic multi-sensor, which can be fitted with passive infrared (PIR) or magnetic plug-in modules. Each unit has a different coverage – the seismic/acoustic detects personnel at a range of 75 meters, the PIR provides directional cues of the target’s direction of movement, with coverage of 30 meters. The magnetic sensor provides a localized indication, detection targets containing ferrous metals at a distance of only 3 meters.
The system uses an open interface which can integrate new types of sensors, including CBRN, meteorological, RF sensors etc. The sensors communicate the target data messages up to 15 kilometers using Low Probability of Intercept/Low Probability of detection (LPI/LPD) VHF communications. Optional repeaters can extend the REMBASS II range up to 150 km. Such sensors are not limited to manual hand emplacement.
REMBASS II based Air Deliverable Remote Sensor System (ADRSS) is currently in development at L3 Communications. When matured, sensors could be deployed by rotary UAVs, Tactical UAVs, or even high speed aircraft. REMBASS II sensors are monitored by an Advanced Monitoring Display System (AMDS) which enables operators to plan missions and depict sensor locations and activities on a graphical display. Sensor data collection can also be performed by a UAV, which also provides users to send data queries to the sensors, over very long distances. The system is also used to control the AN/PPS-5D Ground Surveillance Radar. The system is currently fielded by Stryker Brigade Combat Teams and Special Forces. A subset of the system is the Platoon Early Warning Device (PWED II) system, which uses the basic seismic/acoustic sensor, offering unattended physical security for defensive positions set up by the infantry platoon.