Low level caesium mapping

In 1995 and 1996 selected areas of Latvia was overflown with the Danish equipment for Airborne Gamma-ray Spectrometry. The aim was inter alia to check for and to map the cesium-137 contamination from the 1986 Chernobyl nuclear power plant accident. The measurements showed that the contamination levels were very low- often below 1 kBq/m2. Therefore a new technique for processing of the data had to be developed in order to separate "signal" from noise.