When monitoring walls, ceilings and floors in spaces with extreme conditions, what relates to temperature, humidity, etc., it is not advisable or even possible to place monitoring or measuring equipment in the space itself. The risk of the equipment immediately becoming destroyed or the service life thereof being considerably shortened is very substantial. Conceivable extreme conditions may, for instance, be extreme cold, very strong heat, very high pressures, high air humidity, chemically corrosive substances, other environments not suitable neither for people nor for equipment, and/or a combination of any of the aforementioned environment conditions. Such spaces are usually delimited by non-transparent walls, which makes the monitoring even more difficult.
A closely related technical field and/or solution consist, among other things, of detection and identification of deployed land and anti-personal mines. Here radar technology is used, wherein one or two transmitters transmit signals whereupon a receiver receives the signals reflected by miscellaneous objects in the ground, down to a depth of a meter or so in the ground. An expert has subsequently to study a mapping of the reflected signals and detect, or rather identify, deviations from a common homogeneous volume of sand, soil, clay, stone, etc. However, disadvantages of this method are that the exact location or depth of the feared mine is unknown, and furthermore, the structure and characteristic features of the ground are changed continuously, which makes the detection even more difficult.
Another closely related technical field is monitoring of closed, not accessible spaces, such as military bunkers or demolished houses, in order to detect whether there are persons therein. Also here, radar technology is used, wherein one or two transmitters transmit signals whereupon a receiver receives the signals reflected by miscellaneous objects behind the non-transparent wall. An expert has subsequently to study a mapping of the reflected signals and identify characteristic radar echoes pertaining to a human being. However, the design of the space and the placement of the walls are unknown and are also regarded as unessential in such an operation.