A scanning laser spins a fixed beam such that the beam in effect creates a flat plane. A target supported on a surface being surveyed must be placed such that it is looking at the laser source. The target, by means of a readout can then measure the differential in readings from various points on the surface being surveyed. Thus flatness information can be obtained for as many points as required. An absolute reading of distance from the surface to the laser plane is not obtained, but specialist laser equipment can allow this to be measured.