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I'm a GIS student and in my project I need to generate vegetation indexes. I've generated it succesfully yesterday using both python2.7 and grass gui .I'm using WinGRASS-6.5.svn-r54428-453 on Win7. Today -I don't know why- grass started to generate 1 pixel NDVI map. The formula is as simple as it could be: float(b4-b3)/(b4+b3) as most of you already know. My data is not corrupted, I'd saved original maps somewhere else and it was my first check that whether there is a corruption. Also using QGis 1.8.1 I can generate correct NDVI map with same data. You can check it here:

r.info map=ndvi4@PERMANENT                                                      
 +----------------------------------------------------------------------------+
 | Layer:    ndvi4@PERMANENT                Date: Tue Jan 01 04:06:35 2013    |
 | Mapset:   PERMANENT                      Login of Creator: murat           |
 | Location: newLocation                                                      |
 | DataBase: D:\gis\grassWS                                                   |
 | Title:     ( ndvi4 )                                                       |
 | Timestamp: none                                                            |
 |----------------------------------------------------------------------------|
 |                                                                            |
 |   Type of Map:  raster               Number of Categories: 255             |
 |   Data Type:    FCELL                                                      |
 |   Rows:         1                                                          |
 |   Columns:      1                                                          |
 |   Total Cells:  1                                                          |
 |        Projection: UTM (zone 36)                                           |
 |            N:          1    S:          0   Res:     1                     |
 |            E:          1    W:          0   Res:     1                     |
 |   Range of data:    min = nan  max = nan                                   |
 |                                                                            |
 |   Data Description:                                                        |
 |    generated by r.mapcalc                                                  |
 |                                                                            |
 |   Comments:                                                                |
 |    float(L71175034_03420050627_B40@PERMANENT -                             |
 |    L71175034_03420050627_B30@PERMANENT) /                                  |
 |    (L71175034_03420050627_B40@PERMANENT +                                  |
 |    L71175034_03420050627_B30@PERMANENT)                                    |
 |                                                                            |
 +----------------------------------------------------------------------------+
(Tue Jan 01 04:06:51 2013) Command finished (0 sec)                             

I uninstalled WinGRASS-6.5.svn-r54428-453 and installed WinGRASS-7.0.svn-r54453-453, I've deleted mapset and location and the recrated them also. I couldn't think anything else please give me some information.

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1 Answer 1

up vote 3 down vote accepted

The answer was posted here: http://lists.osgeo.org/pipermail/grass-user/2012-December/066646.html (use g.region to set the output extent).

See also http://grasswiki.osgeo.org/wiki/Computational_region

Note: Please consider to not do parallel postings in mailing lists and here since one of those may remain unanswered, not satisfying the other readers.

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Thanks for notification. I was planning to post the answer to the other platfrom, you preceded me. I'll be careful, you are right. –  GokcenG Jan 1 '13 at 11:20
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No problem :) It is just the race condition between forums and mailing lists... –  markusN Jan 1 '13 at 11:30
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