[GRASS-user] Problem with Lidar Tools

[kaipi]

Dear list,

I am quite new to Grass and need to generate a DSM from Lidar data. Here is
my workflow so far:

v.in.ascii input=f:\lidar_test\single.csv output=single fs=, x=1 y=2 z=3 -z
-b -t --o
v.build single
g.region vect=single
v.in.ascii input=f:\lidar_test\first.csv output=first fs=, x=1 y=2 z=3 -z -b
-t --o
v.outlier input=single output=inlier_s outlier=outlier_s thres_o=5 soe=1
son=1 lambda_i=0.1 --o
v.outlier input=first output=inlier_f outlier=outlier_f thres_o=5 soe=1
son=1 lambda_i=0.1 --o
v.lidar.edgedetection input=inlier_s output=edgedetected see=400 sen=400
lambda_g=0.01 tgh=6 tgl=3 theta_g=0.26 lambda_r=1 --o
v.lidar.growing input=edgedetected output=growing first=inlier_f  tj=0.25
td=0.6 --o
v.lidar.correction input=growing output=classified terrain=terrain sce=5
scn=5 lambda_c=1 tch=2 tcl=1 --o
v.lidar.correction input=classified output=classified_it2
terrain=terrain_it2 sce=5 scn=5 lambda_c=1 tch=2 tcl=1 --o
v.build terrain_it2
v.out.ogr in=terrain_it2 dsn=F:\lidar_test\terrain_it2 format=ESRI_Shapefile 
type=point lco=SHPT=POINTZ -e

v.lidar.edgedetection classifies the data into cat 1 and cat 2 (=Terrain or
Edge ?). This seams to work. The next step is v.lidar.growing. This tool
should classify into 4 categories: TERRAIN SINGLE PULSE, TERRAIN DOUBLE
PULSE, OBJECT SINGLE PULSE or OBJECT DOUBLE PULSE. But this does not happen.
The cats still remain the same (cat1 and cat2) and the output looks
identical to the output from v.lidar.edgedetection. v.lidar.growing seams to
have no effect.
Am I doing something wrong ?

I have another problem with the parameters of the lidar tools (although I
read Brovellis "Managing and processing LIDAR data within GRASS"). Can you
give me some hints how to adjust the default values to very high res Lidar
data (=50 points/m²). I raised see and sen parameter in
v.lidar.edgedetection to 400 with the result, that the detected edges are
now so wide, that they cover complete buildings. This way I can get rid of
the most buildings but the result is not really satisfying and I guess the
problem is false classification of v.lidar.growing

Let me know if you need more infos.

I am using GRass 6.3.0 on Windows. Can I expect improvements switching to
6.4 or switching to Linux ?

Thank you very much !!

kaipi


-- 
View this message in context: http://n2.nabble.com/Problem-with-Lidar-Tools-tp3918684p3918684.html
Sent from the Grass - Users mailing list archive at Nabble.com.