NAMEv.lidar.correction - Correction of the v.lidar.growing output. It is the last of the three algorithms for LIDAR filtering.
SYNOPSISv.lidar.correction v.lidar.correction help v.lidar.correction [-e] input=name output=name terrain=name [sce=float] [scn=float] [lambda_c=float] [tch=float] [tcl=float] [--overwrite] [--verbose] [--quiet] Flags: -e Estimate point density and distance Estimate point density and distance for the input vector points within the current region extends and quit --overwrite Allow output files to overwrite existing files --verbose Verbose module output --quiet Quiet module output Parameters: input=name Input observation vector map name (v.lidar.growing output) output=name Output classified vector map name terrain=name Only 'terrain' points output vector map sce=float Interpolation spline step value in east direction Default: 25 scn=float Interpolation spline step value in north direction Default: 25 lambda_c=float Regularization weight in reclassification evaluation Default: 1 tch=float High threshold for object to terrain reclassification Default: 2 tcl=float Low threshold for terrain to object reclassification Default: 1
DESCRIPTIONv.lidar.correction is the last of three steps to filter LiDAR data. The filter aims to recognize and extract attached and detached object (such as buildings, bridges, power lines, trees, etc.) in order to create a Digital Terrain Model. The module, which could be iterated several times, makes a comparison between the LiDAR observations and a bilinear spline interpolation with a Tychonov regularization parameter performed on the TERRAIN SINGLE PULSE points only. The gradient is minimized by the regularization parameter. Analysis of the residuals between the observations and the interpolated values results in four cases (the next classification is referred to that of the v.lidar.growing output vector): a) Points classified as TERRAIN differing more than a threshold value are interpreted and reclassified as OBJECT, for both single and double pulse points. b) Points classified as OBJECT and closed enough to the interpolated surface are interpreted and reclassified as TERRAIN, for both single and double pulse points.
NOTESThe input should be the output of v.lidar.growing module or the output of this v.lidar.correction itself. That means, this module could be applied more times (although, two are usually enough) for a better filter solution. The outputs are a vector map with a final point classification as as TERRAIN SINGLE PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE PULSE or OBJECT DOUBLE PULSE; and an vector map with only the points classified as TERRAIN SINGLE PULSE or TERRAIN DOUBLE PULSE. The final result of the whole procedure (v.lidar.edgedetection, v.lidar.growing, v.lidar.correction) will be a point classification in four categories: TERRAIN SINGLE PULSE (cat = 1, layer = 2) TERRAIN DOUBLE PULSE (cat = 2, layer = 2) OBJECT SINGLE PULSE (cat = 3, layer = 2) OBJECT DOUBLE PULSE (cat = 4, layer = 2)
EXAMPLESBasic correction procedure v.lidar.correction input=growing output=correction out_terrain=only_terrain Second correction procedure v.lidar.correction input=correction output=correction_bis out_terrain=only_terrain_bis
SEE ALSOv.lidar.edgedetection, v.lidar.growing, v.surf.bspline
AUTHORSOriginal version of program in GRASS 5.4: Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko Reguzzoni Update for GRASS 6.X: Roberto Antolin and Gonzalo Moreno
REFERENCESAntolin, R. et al., 2006. Digital terrain models determination by LiDAR technology: Po basin experimentation. Bolletino di Geodesia e Scienze Affini, anno LXV, n. 2, pp. 69-89. Brovelli M. A., Cannata M., Longoni U.M., 2004. LIDAR Data Filtering and DTM Interpolation Within GRASS, Transactions in GIS, April 2004, vol. 8, iss. 2, pp. 155-174(20), Blackwell Publishing Ltd. Brovelli M. A., Cannata M., 2004. Digital Terrain model reconstruction in urban areas from airborne laser scanning data: the method and an example for Pavia (Northern Italy). Computers and Geosciences 30 (2004) pp.325-331 Brovelli M. A. and Longoni U.M., 2003. Software per il filtraggio di dati LIDAR, Rivista dell?Agenzia del Territorio, n. 3-2003, pp. 11-22 (ISSN 1593-2192). Brovelli M. A., Cannata M. and Longoni U.M., 2002. DTM LIDAR in area urbana, Bollettino SIFET N.2, pp. 7-26. Performances of the filter can be seen in the ISPRS WG III/3 Comparison of Filters report by Sithole, G. and Vosselman, G., 2003. Last changed: $Date: 2010-09-16 09:25:59 +0200 (Thu, 16 Sep 2010) $ Full index (C) 2003-2010 GRASS Development Team V.LIDAR.CORRECTION(1)