[GRASSLIST:7176] RE: Gettting off the ground with v.surf.rst
tom_colson at ncsu.edu
Wed Jun 15 22:30:34 EDT 2005
Thanks for the quick reply. I seem to have gotten it working, however
verrryyyyy sloowwwlllly on a 2.4 GHZ machine, 1 GB RAM. Any chance the rst
code has been optimized for 64 bit?
The below syntax took about 30 minutes to run....one tile of LIDAR
data...Andy, I think you and I will be working on the same dataset (entire
neuse) at one run...read the paper on RST and the various parameters, but
can't seem to find a groove that doesn't bring my workstation to it's knees.
Read in archives of people getting millions of points done in minutes!
GRASS 6.1.cvs (counties):~ > g.region vect=grid_0793 res=10
GRASS 6.1.cvs (counties):~ > g.region -pm
projection: 99 (Lambert Conformal Conic)
ellipsoid: a=6378137 es=0.00669438
v.surf.rst input=grid_0793 layer=0 zcolumn=flt1 dmax=24.998895
dmin=4.999779 elev=elev_0973 zmult=1.0 tension=40. smooth=0.1 segmax=10
Authors: original version - H.Mitasova, L.Mitas, I. Kosinovsky, D.P. Gerdes
See manual pages for reference and publications T3
Percent complete: Reading lines from vector map ...
Reading nodes from vector map ...
Warning: ignoring 610 points -- too dense
(Why are we dropping 610 points? Could these all be in one place?)
The number of points from vector file is 308552 The number of points outside
of region 0 The number of points being used is 307942
Processing all selected output files
will require 4949732 bytes of disk space for temp files Percent complete:
North Carolina State University
Department of Forestry and Environmental Resources
(919) 673 8023
tom_colson at ncsu.edu
From: Andrew Danner [mailto:adanner at cs.duke.edu]
Sent: Wednesday, June 15, 2005 3:42 PM
To: tom_colson at ncsu.edu
Cc: grasslist at baylor.edu
Subject: Re: [GRASSLIST:7173] Gettting off the ground with v.surf.rst
Some of your parameters seem a bit odd, mainly dmin, segmax, and npmin seem
way too high. What is your grid resolution from g.region -p?
Typically dmin is set to be 1/2 of the grid resolution so if you want a 20
meter resolution surface, try a dmin of 10. Decreasing dmin typically
increases the number of points used for the interpolation. Since your dmin
is high and your point count is low, I would look into adjusting dmin first.
Once you fix that though, you may find that the interpolation step takes
forever, mostly because segmax and npmin are set quite high as well. For
LIDAR data from NCfloodmaps or LDART I typically use npmin=100 and
segmax=20. The running time of the interpolation is roughly proportional to
(n/segmax)*npmin^3, so cutting both npmin and segmax in half makes the
program run about 4 times faster.
See if that helps.
On Wed, 2005-06-15 at 14:52 -0400, Thomas Colson wrote:
> this may appear to be a stupid question, but I'm having a hard time
> getting the "desired" output from v.surf.rst, and I don't want to run
> downstairs and bother Dr. Mitasova with such a menial question....
> I have a x,y,z vector of LIDAR elevation data, and I'm trying to get a
> raster elevation surface based on the z col. I've tried many different
> variations of the output below, with the same errors "The number of
> points being used is 3 " and so forth. I'm sure this has been done
> many times by someone in the know, any chance of an example command
> syntax so I can get this running?
> v.surf.rst input=lidar3 layer=0 zcolumn=flt1 dmax=100000 dmin=10000
> elev=surf7 zmult=1.0 tension=40. smooth=0.1 segmax=400 npmin=2000
> Authors: original version - H.Mitasova, L.Mitas, I. Kosinovsky, D.P.
> Gerdes See manual pages for reference and publications T3
> Percent complete: Reading lines from vector map ...
> Reading nodes from vector map ...
> Warning: strip exists with insufficient data
> Warning: ignoring 348352 points -- too dense
> WARNING: 3 points given for interpolation (after thinning) is less
> than given NPMIN=2000 Warning : there is less than 2050 points for
> interpolation, no segmentation is necessary, to run the program
> faster, set segmax=2050 (see
> The number of points from vector file is 348355 The number of points
> outside of region 0 The number of points being used is 3
> Processing all selected output files
> will require 1612 bytes of disk space for temp files Percent complete:
> history initiated
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