SUBTERRANEAN ELECTROMAGNETIC FIELD
Cables are installed underground to set up a discrete electromagnetic proximity detection field. Two cables are generally installed in transmit and receive configuration.
The system detects distortion within its field and annunciates alarm conditions. Targets are detected based on their conductivity, size and movement. Smaller targets, such as small animals, do not meet the minimum requirements and are ignored. Most systems operate through vegetation such as grass, bushes and trees.
Conductivity is related to moisture content which means that these systems are sensitive to fog and standing water. Although they are ideal for following undulating terrain, care needs to be taken in low lying areas.
In order to get the maximum efficiency from such a system it is important to install it correctly. That is to say that the two cables must remain parallel at all times and at the same depth in the ground. Prior to installation, it is recommended that a ground survey is carried out to determine the optimum spacing for the cables, which is dependent on the ground type. The ground conditions may vary around the site.
Subterranean detection can be installed on either side of a physical barrier or in open space. It can be buried in a variety of materials, including asphalt, block paving, gravel and lawn. These systems are ideally suited for areas that need covert detection such as lawns and open spaces or areas that cannot have their aesthetics disturbed. This form of detection can follow irregular ground profiles both horizontally and vertically and has the advantage of detecting above the ground within the electromagnetic field, radiating to an average height of 1m.