[GRASS-dev] [GRASS GIS] #2564: r.what: remove 400 maps limit and add some new output options

Blumentrath, Stefan Stefan.Blumentrath at nina.no
Thu Jan 29 14:43:14 PST 2015

Hi Sören,

Thanks a lot for that one. Great work as usual. It works really nice and fast.
I compared it to point sampling of (in-db) raster data in PostGIS, where I have exactly the same data (uploaded to PostGIS from TGIS/GRASS).
I sampled 686 raster map (1500x1300 pixels) at 17 points.
PostGIS (with spatial index): 53 seconds
t.rast.what (with 2 workers): 59 seconds
I had some minor issues in my rather old GRASS71 installation.

Please find attached a diff for the things I had to change in order to make it work. However, with "col"-option all coordinates in the header are the same. This I did not manage to fix (yet).

Kind regards,

P.S.: BTW, is the structure of the TGIS-database for current GRASS70 the same as for  GRASS71?

-----Original Message-----
From: grass-dev-bounces at lists.osgeo.org [mailto:grass-dev-bounces at lists.osgeo.org] On Behalf Of GRASS GIS
Sent: 29. januar 2015 00:16
Subject: Re: [GRASS-dev] [GRASS GIS] #2564: r.what: remove 400 maps limit and add some new output options

#2564: r.what: remove 400 maps limit and add some new output options
 Reporter:  sbl          |       Owner:  grass-dev@…              
     Type:  enhancement  |      Status:  new                      
 Priority:  normal       |   Milestone:  7.1.0                    
Component:  Raster       |     Version:  svn-trunk                
 Keywords:  r.what       |    Platform:  Unspecified              
      Cpu:  Unspecified  |  

Comment(by huhabla):

 I have just committed a new temporal module called t.rast.what in trunk
 (r64349 - r64351) that utilized r.what to sample space time raster  datasets using vector points. It provides three output layouts that  transforms the r.what output into row or column layouts. It can run  several r.what processes in parallel using a maximum of 400 raster map  layer in a single r.what process.

 Please have a look at it.

 Any feedback about its performance, usefulness and handling is highly  welcome.

 Improving r.what to allow more than 400 maps is simple, just edit the  fixed value in the source. But, editing this value may cause open file  handler limit problems with your OS. However, these limits can be adjusted  at kernel level configuration for Linux.

 Implementing a more intelligent file handling solution requires more  effort.

Ticket URL: <http://trac.osgeo.org/grass/ticket/2564#comment:1>
GRASS GIS <http://grass.osgeo.org>

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