Re: [GRASS-user] Creating Raster Subsets in GRASS 7.0.0

[Micha Silver]

Hi Jake Excuse for butting in... On 05/12/2015 05:23 PM, Jake Chila wrote: Hi Moritz, I definitely did mean 'g.region -p', sorry for that. I ended up getting it to work using 'r.mapcalc' after setting the region. I saw someone online had used it with the simple _expression_ newmap=oldmap. Then, when I export the newmap it is only of the subset. This small workaround was easy to set up, but I don't have any idea why it didn't work in the first place.  It's not a "workaround". The correct way to clip a section of a raster is two steps: define the new region with g.region, then run r.mapcalc (which honors the region settings) to get a new raster, at the new region settings, with values equal to the original. However, in your r.info output below, something seems wrong with the resolution. The landsat imagery is at 30 meters resolution. WHere did the (very small) values below come from? And why is the N-S 6 times smaller than the E-W ??    r.info returns: (Tue May 12 11:19:01 2015)                                                       r.info map=L5_2007_ATCOR_COMP@Jacob                                               +----------------------------------------------------------------------------+  | Map:      L5_2007_ATCOR_COMP@Jacob       Date: Mon May 04 14:31:43 2015    |  | Mapset:   Jacob                          Login of Creator: Jacob           |  | Location: FordingRiver                                                     |  | DataBase: C:\Users\Jacob\Documents\grassdata                               |  | Title:     ( L5_2007_ATCOR_COMP )                                          |  | Timestamp: none                                                            |  |----------------------------------------------------------------------------|  |                                                                            |  |   Type of Map:  raster               Number of Categories: 0               |  |   Data Type:    CELL                                                       |  |   Rows:         11374                                                      |  |   Columns:      12191                                                      |  |   Total Cells:  138660434                                                  |  |        Projection: UTM (zone 11)                                           |  |            N:     557000    S:     554300   Res: 0.23738351                |  |            E:     659000    W:     642200   Res: 1.37806579                |  |   Range of data:    min = 0  max = 32767                                   |  |                                                                            |  |   Data Description:                                                        |  |    generated by r.composite                                                |  |                                                                            |  |   Comments:                                                                |  |    r.composite red="GRASS_ATCOR_2007_B3@Jacob" green="GRASS_ATCOR_2007_\   |  |    B2@Jacob" blue="GRASS_ATCOR_2007_B1@Jacob" levels=32 output="L5_2007\   |  |    _ATCOR_COMP"                                                            |  |                                                                            |  +----------------------------------------------------------------------------+ (Tue May 12 11:19:02 2015) Command finished (0 sec) However, I have encountered a new problem. On one of my ETM+ images, the subset is returned as an empty raster. The process runs fine on the other ETM+ image from one year earlier but for some reason, the subset from the scene one year later has a min and max data range of 'NULL'. This range appears to be constant across all the other scenes, so is there a way for me to quickly edit this scene so it has the correct data?  As before, I would double check "g.region -p", and "r.info" for both the original Landsat image, and the clipped image that comes out NULL. Thanks, JDC On Tue, May 12, 2015 at 3:33 AM, Moritz Lennert <mlenn...@club.worldonline.be> wrote: On 08/05/15 19:13, Jake Chila wrote: Hey all, I am currently working with some landsat data in Grass 7.0.0 on windows 7, and am trying to hone in on my study area (much smaller than the whole scene). From what I can tell, the best way to do this is through the 'g.region' command however, I am having significant problems getting this module to run correctly. my input is: g.region n=5572425 s=5536865 e=655050 w=626350 res=30 One thing is that it runs in '0 seconds' so I think that is a little odd. It's normal as the command just changes a few entries in a text file, so it is really fast. When I use the 'g.region -d' command I can see that everything is set properly, Did you maybe mean g.region -p ? At least this is the command you should use to check current region settings. however when I update the map display nothing changes. Also, when I export the file using 'r.out.gdal' it exports nothing. ('r.out.gdal -t -f --overwrite input=LT5_2007_ATCORRCOMP@May_Project output=C:\Users\Jacob\Desktop\GRASS_Trials\exportattempt5 format=GTiff type=Uint16 nodata=0) That should normally respect the region settings. What does r.info LT5_2007_ATCORRCOMP give you ? Moritz This mail was received via Mail-SeCure System. _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System.

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