Accuracy Assessment of Laser Scanning Data: a Case Study

A method is described for the estimation of planimetric precision of laser scanning data. Due to the nearly random distribution of the points hit by the laser, it is difficult to use the very standard technique of measuring the same points with the instrument under investigation and with another one, whose performances are well known and better than those expected from the former. A new approach is necessary and ours is based on surfaces, rather than points; we measure flat and slope surfaces previously acquired with laser scanning, with very accurate ground surveying methods; we use their equations to validate the laser points inside. Flat surfaces are used for the altimetric error estimation, while slope ones are used for the estimation of the planimetric accuracy. Indeed when the terrain is not flat, it could be said that the planimetric errors affect altimetric precision of the points measured by the laser scanner; we will show exactly what this means; we will also show that this behaviour can be exploited to estimate planimetric precision, provided that the shape, position and attitude of some ramps is known. The paper first of all focuses on the method’s description, then it shows some results obtained from Pavia’s test area.