[GRASSLIST:4238] GRASS 5.7.0 (2004) - v.surf.rst strange behaviour
Javier A. Yebrin
javier.yebrin at ing.unitn.it
Tue Aug 24 08:48:39 EDT 2004
Hi all!
I'm trying to interpolate a laser-altimeter survey in order to fill null
areas. I've mainly followed by hand the procedure contained in the script
r.fillnulls .
The problem arises after the v.surf.rst module because the resulting
elevation map is at a very first glance not correct: it looks like a ramp,
the height values increasing linearly from North to South leading to absurd
values such as 300000 meters at the bottom part...
The lidar survey is a floating point map and it has been resampled to a
3mx3m grid.
These are the steps:
1. Creating and growing a MASK for the null values
r.mapcalc temp_raster="if(isnull(LIDAR))"
r.grow in=temp_raster out=MASK
2. Vectorize the raster file: here i get a warning. Should i care?
r.to.vect -v in=LIDAR out=temp_vector feature=point
WARNING: Raster is not CELL, '-v' flag ignored, raster values will be
written to the table.
Just to verify, a simple d.what.vect gives:
map: 'temp_vector'
mapset: 'javier'
feature type: Point
field: 1
category: 221891
driver: dbf
database: /grassdata/tovel_utm32/javier/dbf
table: temp_vector
key column: cat
cat : 221891
value : 1461.560059
3. Interpolate the points with RST
v.surf.rst in=temp_vector elev=interp_raster
4. View results. This is the history file for interp_raster(note zmin and
zmax)
Tue Aug 24 16:25:01 2004
interp_raster
javier
javier
raster
vector file temp_vector
generated by v.surf.rst
tension=40.000000, smoothing=0.100000
dnorm=96.007102, dmin=1.500000, zmult=1.000000
segmax=40, npmin=200, rmsdevi=1.734224
zmin_data=1.000000, zmax_data=324402.000000
zmin_int=-9.806899, zmax_int=324404.267325
Any ideas?
Thanks in advance
Javier Yebrin
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