Thanks for your help ! Unfortunately I still don't get satisfying results with the Lidar tools. Here is what I have done so far:
- Updated to 6.4 on Windows: v.outlier doesn't work (see my post in Win Grass forum) - Installed Grass 6.4 RC 5 on Ubuntu (Ubuntu package): same results like on Windows Grass 6.3 - Decreased spline steps to 0.04: v.outlier and v.lidar.edgedetection give errors. My results are better the higher the spline steps are (> 20). Brovelli recommends spline step 3 up to 4 times of the planimetric resolution. AFAIK planimetric resolution means points per m². If I have 50 pts/m² this would mean a spline step of 200 ?? With spline steps about 20 I get nice edges and with spline step of 400 complete buildings are detected as edges. - Tried the Lidar demo data (nc_spm_08_2008_may18) and followed the instructions on the Micro-tutorial_for_LIDAR_data_analysis: v.lidar.edgedetection took so long, that I canceled process after 1 h (input file has only 2000-3000 points - so something must be wrong) I have also a problem to understand the definitions of first and last return data. Here is a part of my Lidar data (ASCII format converted from raw LIdar binary): 0 lon lat height intensity last first 1 3360422.27 5825275.62 37.16 255 1 1 2 3360421.94 5825275.60 38.21 56 0 1 3 3360422.48 5825275.60 37.18 255 1 0 4 3360422.17 5825275.58 38.18 141 0 1 5 3360422.65 5825275.58 37.26 255 1 0 6 3360422.84 5825275.56 37.31 255 1 1 7 3360423.05 5825275.54 37.32 255 1 1 8 3360423.36 5825275.52 37.13 255 1 1 9 3360423.06 5825275.50 38.11 12 0 1 10 3360423.60 5825275.50 37.09 255 1 0 11 3360423.70 5825275.49 37.32 255 1 1 First and last returns can be true (1) or false (0) or both. My understanding is, that all points that have first return=true are first returns and all returns that have last=true are last returns. When first and last are true we have a single pulse otherwise we have double pulses. If I understand the microtutorial correctly I need for v.lidar.growing as input the last return single pulses (last=true and first=false) and as first all pulses with first=true. But I get better results when I use as input all last return pulses (only last=true) and as input only the first single pulses (first=true and last=false). I still have the problem that v.lidar.growing does not change categories. Output has only 2 categories - same as output of v.lidar.edgedetection. I have attached two screenshots of my results so far (using the parameters in my first post). I have not yet run v.surf.bspline. http://n2.nabble.com/file/n3928180/lidar_before_after.jpg Classification after v.lidar.edgedetection: http://n2.nabble.com/file/n3928180/edgedetected.jpg Any ideas regarding v.lidar.growing ? Thanks - Kaipi -- View this message in context: http://n2.nabble.com/Problem-with-Lidar-Tools-tp3918684p3928180.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
