[GRASS-dev] r.resample.rst behavior does not match manual

[Michael Barton]

Thanks for the clarification Stefan.

It sounds like, unlike other resampling commands (unless they, too, are in error), r.resample.rst needs to be run at the resolution of the original map, not the output map. The output resolution will be determined by the command, not by the region settings. This should go into the manual too, along with the revised text you suggested.

In a somewhat related question, do you have any idea how r.resample.filter works? The manual is not very informative and I couldn’t get any useful downscaling results (lower to higher resolution) with my spot tests.

r.resample.interp doesn’t seem to give expected results either. I’ll do a test with demo data when I have a few minutes this week. I did get very good downscaling results with r.resample.bspline, but it took a very long time.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice:  480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu















On Aug 30, 2015, at 12:54 AM, Blumentrath, Stefan <Stefan.Blumentrath at nina.no<mailto:Stefan.Blumentrath at nina.no>> wrote:

Hi Michael,

The second sentence you cite from the manual seems indeed a bit imprecise.
It should probably say something like:
“The extent of all resulting raster maps is taken from the settings of the current region (which may be different from the extent of the input raster map). The resolution of the current region however has to follow cleanly the resolution of the input map”

Yet, the example in the manual is correct. It might be modified in order to highlight the module behavior named above by exchanging the first g.region command by something like:

g.region n= s= e= w= align=elevation.dem -p
(I do not have the sample data available, so I cannot guess reasonable extent values or another raster or vector map with a smaller extent)…

Cheers
Stefan

From: grass-dev-bounces at lists.osgeo.org<mailto:grass-dev-bounces at lists.osgeo.org> [mailto:grass-dev-bounces at lists.osgeo.org] On Behalf Of Michael Barton
Sent: 30. august 2015 04:03
To: GRASS developers grass-developers <grass-dev at lists.osgeo.org<mailto:grass-dev at lists.osgeo.org>>
Subject: [GRASS-dev] r.resample.rst behavior does not match manual

The r.resample.rst manual states…

" Reinterpolation (resampling) is done to higher, same or lower resolution specified by the ew_res and ns_res parameters.”

The very next sentence states...

"All resulting raster maps are created using the settings of the current region (which may be different from that of the input raster map).”

So these two sentences contradict each other.

Additionally, I’ve got a 90m DEM that I want to resample to 30m. I’ve reset the region resolution to 30m. This is exactly the situation listed in the second sentence. Yet r.resample.rst gives the error:

"ERROR: Input map resolution differs from current region resolution!"

So what is the proper way to use this module? Whatever it is, the manual needs to be corrected.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice:  480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu<http://csdc.asu.edu/>

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