[GRASS5] [bug #3826] (grass) two r.resamp.rst issues

[Michael Barton]

Perhaps we misunderstand each other, or maybe it works for you.

The whole point of the module is to change the resolution of the raster map.
In my recent experience (I've tried it on a Mac and on Fedora Core 4), this
doesn't seem to work, regardless of the region settings when you run the
module. It changes the resolution, but it seems to have the effect of simply
making more grid cells without correctly interpolating between them. For
example, going from a 30m resolution DEM to a 15m resolution using
r.resamp.rst seems to produce 4 15m cells within the area of an original 30m
cell, but each of the 15m cells has the same resolution as the original
cell. This is not how it should work.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ 85287-2402

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton



> From: Jaro Hofierka <hofierka at geomodel.sk>
> Date: Sun, 13 Nov 2005 23:20:06 +0100
> To: Michael Barton <michael.barton at asu.edu>
> Cc: <grass5 at grass.itc.it>, Helena Mitasova <hmitaso at unity.ncsu.edu>
> Subject: Re: [GRASS5] [bug #3826] (grass) two r.resamp.rst issues
> 
> 
> Michael Barton wrote:
>> Hamish,
>> 
>> We've run into that here too. One of my RA's did a test of interpolating to
>> a higher resolution using r.resamp.rst and the more complicated procedure of
>> generating a large number of points from a raster map, and then
>> interpolating from the points to a higher resolution.
>> 
>> r.resamp.rst is faster and more straightforward. BUT (a VERY big but), it
>> behaves exactly as you describe. It simply turns out a map that looks just
>> like the original map is subdivided into more grid cells, without any
>> interpolation. This makes the module essentially useless.
> 
> It's not useless because if you run the module at a resolution equal to
> the input raster map, the result is OK.
> The warning message should be replaced by a fatal error that exits the
> command.
> 
> Jaro
> 
>> 
>> Michael
>> __________________________________________
>> Michael Barton, Professor of Anthropology
>> School of Human Evolution and Social Change
>> Arizona State University
>> Tempe, AZ 85287-2402
>> 
>> phone: 480-965-6213
>> fax: 480-965-7671
>> www: http://www.public.asu.edu/~cmbarton
>> 
>> 
>> 
>> 
>>> From: Request Tracker <grass-bugs at intevation.de>
>>> Reply-To: Request Tracker <grass-bugs at intevation.de>
>>> Date: Sat, 12 Nov 2005 13:37:05 +0100 (CET)
>>> To: <grass5 at grass.itc.it>
>>> Subject: [GRASS5] [bug #3826] (grass) two r.resamp.rst issues
>>> 
>>> this bug's URL: http://intevation.de/rt/webrt?serial_num=3826
>>> -------------------------------------------------------------------------
>>> 
>>> Subject: two r.resamp.rst issues
>>> 
>>> If you run r.resamp.rst at a resolution other that that of the input map,
>>> the
>>> output elev map is not created at the specified ew_res= and ns_res=
>>> resolution.
>>> A warning is given that you are doing so, but it doesn't mention why that
>>> might be bad. Interestingly the output map is actually written at the target
>>> resolution, but it contains the data resolution from the original map.
>>> (target
>>> was 50m, original was 100m)
>>> 
>>> If the input map is in another mapset (map at othermapset) then it gives an
>>> error
>>> that the input map can't be found. (happens when it tries to copy the color
>>> table I think) and exits with an error. (but processing is already done so
>>> output map is ok, just without a colortable)
>>> 
>>> 
>>> Hamish
>>> 
>>> 
>>> ps - I've tidied up the module's code and strings a bit in CVS, so cvs
>>> update
>>> before fixing...
>>> 
>>> 
>>> -------------------------------------------- Managed by Request Tracker
>>> 
>>> 
>>> 
>> 
>> 
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>>