Mobile non ionizing radiation measurement system

Most regulations ask for levels of EM radiation in an area surrounding telecommunications installations. These might interest close neighbors but does not help in the risk perception of population at large. That is what makes interesting measurements on a geographic basis, that is, covering an area with certain minimum resolution. Until now this has been done statically, that is on fixed positions such as city road intersections. That equals one measurement each city block or a spatial resolution of 100 points/km2. On our experience, with an acquisition time of 6 minutes/point we do from 6 to 10 points/h or 10 to 17 h/km2. On a dynamic or mobile system we acquire simultaneously the signal from a GPS and synchronize it with the NIR measuring equipment in a portable computer. This way each measurement can be associated with a position and time. Now speed of acquisition will depend on sampling time at the meter, selectable from 0.4 to 2 sec, and displacement velocity. During acquisition we simply get a table of values. To display them in convenient form for the public at large, we utilized commercial mapping software and satellite images. We found that 4 measurements for each city block is the maximum acceptable for a reasonably meaningful display of results. A scale of colors will indicate value, where green will indicate low ones, yellow for intermediates and red for values above permitted levels. Nevertheless, since actual values are mostly well below limits, we use a scale of greens to remark small differences as we move. The system was tested on selected areas of Cordoba, population 1,3 million. With an average ''cruising speed'' of 36 km at the transport vehicle, acceptable for normal traffic conditions, we achieved 440 points/m2 in less than 20 min. Since common GPS receivers have systematic static errors on the order of +/- 6 meters plus a drift with time, our mapping must be corrected after acquisition, typically adjusted to the city streets where we circulated. Repeatability can be verified by simply repeating the same road shortly after since mobile communications vary as randomly with time as their users and will follow citizen habits such as lunch time or working hours. Conclusions: - The mobile/dynamic system permits execution times dramatically shorter than static method with the obvious benefit in cost. - The increase in resolution improves risk perception of the population. Now every neighbor within the surveyed area will have a measurement point practically in his front door. - The method can be utilized to detect installations which are either non declared or simply not included in the latest official listings, always so difficult to keep up to date in large urban conglomerates. (author)