Terrestrial laser scanner error quantification for the purpose of monitoring

In this paper, TLS error sources are discussed and the types and magnitudes of these errors are observed. Furthermore, a procedure for eliminating laser scanner outliers and reducing noise is introduced. For this purpose, two TLS instruments have been examined: Leica Scanstation P20 and P40. The results of the tests reveal the average noise level (mean errors) between two scans can be improved by using a surface model rather than direct point to point differencing, with improvements from 2.8 mm to 1.7 mm and from 0.7 mm to 0.2 mm for P20 and P40 respectively. In addition, the best fit local planes technique can remove outliers without reducing point density. Therefore, the maximum errors decreased from 50 mm (due to outliers) to 11 mm and from 13 mm (due to outliers) to 1 mm for P20 and P40 respectively.