The absolute value of the radar cross section depends on the transceiver card and the involved amplifiers. When displaying it as relative figure, it is depicted in dBm² (meaning dB multiplied m²).
The decibel (symbol: dB) is a relative unit of measurement corresponding to one tenth of a bel (B). It is used to express the ratio of one value of a power or field quantity to another, on a logarithmic scale, the logarithmic quantity being called the power level or field level, respectively. Two signals whose levels differ by one decibel have a power ratio of 101/10 (approximately 1.25893) and an amplitude (field quantity) ratio of 101⁄20 (1.12202). Based on this definition, 0 dBm² stands for the RCS of 1 m².