The invention relates to the detection of surfaces of sections of the ground based on a scanning beam, by means of evaluation of the reflected received scanning beam. The scanning beam is formed from the useful signal beam of an external system and/or provided by one or more satellites (1), GPS L-band or DBS C-band. The invention provides for means for detecting the surface condition in relation to the type and condition of road surface covering. Polarisation conditions are compared with the unreflected reference at stationary beacons (5) using autocorrelation and FFT for a static classifier. Examples of types of surfaces and conditions are asphalt, tar, sand, gravel and paving stones, dry or wet conditions and ice and snow.