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While radars and IR scanners are effective
for open area surveillance, urban combat poses distinct environmental
challenges for troop protection. Special sensors are designed for such
applications. For example, sensors are required to trigger an alarm
when movement is detected inside a specific building or room, which
could otherwise be considered as "clean". Other sensors are designed
to "look through walls" and identify human presence, movement beyond
etc.
 Ground sensors designed for urban operations
are usually multi-sensor packages; their communications are designed
to overcome the obstacles and multi-path reflections of urban terrain,
and camouflaged to mimic common urban terrain features. An example is
the Miniature Unattended Ground Imager (MUGI), developed by Seraphim.
It provides covert, persistent visual surveillance of a target using
periscopic EO, NIR and IR imaging devices, fitted with internal pan,
tilt and zoom, As the device has no external movement the system can
blend into the surrounding scene for covert operation. The device can
remain in the field, delivering up to 10 days of imaging without
battery replacement. BAE Systems
has integrated a collection of four types of sensors for the US Army
including Moving Target Indicator (MTI) Radar, Magnetic, Seismic, and
Single Pixel IR packed into an integrated sensor unit. The unit will
monitor its surrounding area and send reports to the user’s pager,
PDA, or laptop PC. The different sensors are selected to match the
specific environment. For example, where radar is blocked by metal
siding, seismic and magnetic sensors can provide comparable coverage.
The seismic sensor can also be highly effective to identify footsteps
in a wood frame building but though unable to provide a direction or
distance of such movement. The single pixel IR can localize the
direction of a human if there is no blockage. By deploying different
types of sensors, virtually uninterrupted coverage can be obtained. (continue...)
Sniper Detectors
 Other sensors are used to identify fire sources to facilitate
quick and effective response. Such systems utilize both acoustic and
EO sensors. These systems measure azimuth, elevation and distance of a
sniper or small arms firing source. An example is the Viper
Counter-Sniper System, developed in the mid 1990s for the US Naval
Research Lab for counter-sniper activity. Viper is comprised of an
infrared camera automatically detecting muzzle flash signature
distinctive of small arms fire. A television camera with high power
zoom provides target identification, and fire control. The system can
be integrated with remotely controlled counterfire payload, which can
mount lethal or less lethal means. Viper can be employed on fixed
sites or in a vehicular installation. The system detects rifle fire
within seventy milliseconds of its occurrence, during this time a
supersonic bullet would travel less than 50 meters. A different system
developed by RAFAEL is the
Spotlite - a high precision, IR sensor capable of detection of
small arms fire sources. The system detects multiple small arms/sniper
fire sources simultaneously, day and night, at long distances.
Spotlite analyzes the fire sources detected, verifying that it is
actually enemy fire. Once verified, target parameters (type, location,
elevation etc) are transferred to snipers and other weapon systems,
thereby closing the sensor-to-shooter loop quickly and efficiently.
Similar camera-based systems such as the Pivot system are integrating
a camera and an acoustic detector (Pilar).
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