[GRASS-user] r.patch for stitching rasters?

[Dylan Beaudette]

Hi Boris,

Went back to a large file which was created with r.patch, which had
the following region settings:

Data Type:    DCELL
Rows:         30912
Columns:      20239
Total Cells:  625627968

If I recall, this took about 20 minutes to complete on a Xeon 3.2 Ghz
machine, running Debian Linux, with 1 Gb RAM.

Cheers,

Dylan


On 11/17/07, Boris Avdeev <borisaqua at gmail.com> wrote:
> Well, you assuming that NULL=0, but the sole reason for having NULL
> layer in grass is that those values are not identical.
>
> Boris
>
> On Nov 16, 2007 5:55 PM, Charles Ehlschlaeger
> <c.ehlschlaeger at insightbb.com> wrote:
> > > I couldn't figure out how to make gdal_merge output NULLs
> > > instead of 0s (and what formats support NULLs?).
> >
> > r.mapcalc can easily convert your 0s into NULLS with the expression:
> >
> > newmap = if(map == 0, null(), map)
> >
> > r.mapcalc will solve most raster problems. GRASS users are advised to know
> > that program inside and out.
> >
> > Sincerely, chuck
> >
> > Chuck Ehlschlaeger, Associate Professor of Geography
> > Western  Illinois  University
> > 215 Tillman Hall, 1 University Circle, Macomb, IL 61455
> > cre111 at wiu.edu, phone: 309-298-1841, fax: 309-298-3003
> >
> >
> > -----Original Message-----
> > From: grass-user-bounces at lists.osgeo.org
> > [mailto:grass-user-bounces at lists.osgeo.org] On Behalf Of Boris Avdeev
> > Sent: Friday, November 16, 2007 1:11 PM
> > To: dylan.beaudette at gmail.com
> > Cc: grass-user at lists.osgeo.org
> > Subject: Re: [GRASS-user] r.patch for stitching rasters?
> >
> > Yes, though I couldn't figure out how to make gdal_merge output NULLs
> > instead of 0s (and what formats support NULLs?).
> > But anyway, you think that this is normal performance?
> >
> > On Nov 16, 2007 2:08 PM, Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
> > > On Friday 16 November 2007, Boris Avdeev wrote:
> > >
> > > > Now, when you asking...
> > > > Now it is this:
> > > >
> > > > projection: 3 (Latitude-Longitude)
> > > > zone:       0
> > > > datum:      wgs84
> > > > ellipsoid:  wgs84
> > > > north:      48:50:24.701676N
> > > > south:      34:38:56.353164N
> > > > west:       45:57:00.735336E
> > > > east:       55:00:56.276712E
> > > > nsres:      0:01:00.033312
> > > > ewres:      0:00:59.991804
> > > > rows:       851
> > > > cols:       544
> > > > cells:      462944
> > > >
> > > > But I believe that at the time I started r.patch it was this:
> > > >
> > > > projection: 3 (Latitude-Longitude)
> > > > zone:       0
> > > > datum:      wgs84
> > > > ellipsoid:  wgs84
> > > > north:      46N
> > > > south:      35N
> > > > west:       35E
> > > > east:       55E
> > > > nsres:      0:00:03
> > > > ewres:      0:00:03
> > > > rows:       13200
> > > > cols:       24000
> > > > cells:      316800000
> > > >
> > > > since I was trying to preserve resolution of original srtms.
> > > >
> > > > Boris
> > > >
> > >
> > > That is pretty big, but not impossibly big. Have you considered something
> > like
> > > gdal_merge.py for merging the files outside of GRASS ?
> > >
> > > cheers,
> > >
> > > Dylan
> > >
> > >
> > > >
> > > > PS Sorry Dylan
> > > >
> > > > On Nov 16, 2007 12:49 PM, Dylan Beaudette <dylan.beaudette at gmail.com>
> > wrote:
> > > > > On Friday 16 November 2007, Boris Avdeev wrote:
> > > > > > Hello grass (ab)users!
> > > > > > I am using r.patch to merge 200 1 degree, 3 seconds resolution
> > srtm's
> > > > > > (1-2 Mb each). After 24 hours of real time and 20 hours of Xeon
> > > > > > processor time I have 39% completed! My guess that this task
> > shouldn't
> > > > > > take so long. Is r.patch a wrong tool to do this thing? Or is it a
> > > > > > bug? I am using grass-6.3.cvs.
> > > > > >
> > > > > > Thanks,
> > > > > > Boris
> > > > >
> > > > > check region extents and resolution ... can you send the output from
> > > > > g.region -p ?
> > > > >
> > > > > Dylan
> > > > >
> > > > >
> > > > > --
> > > > > Dylan Beaudette
> > > > > Soil Resource Laboratory
> > > > > http://casoilresource.lawr.ucdavis.edu/
> > > > > University of California at Davis
> > > > > 530.754.7341
> > >
> > >
> > >
> > > --
> > >
> > > Dylan Beaudette
> > > Soil Resource Laboratory
> > > http://casoilresource.lawr.ucdavis.edu/
> > > University of California at Davis
> > > 530.754.7341
> > >
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