[GRASS-user] Error: Grass and Grass Plugin in QGIS

GRASS GRASS user
,
1

Hello everyone,
I'm starting to use GRASS, and of course, I'm starting to have some
problems. One of these concerns the values ​​of the pixel of an image. If I
open a satellite image with ENVI, ArcMap, GRASS,QGIS I get the same values
of the pixel of the image, but if I open it with the GRASS plugin in QGIS, I
get different values for the same pixel! So, if I compare the same pixel I
get two different values: 1 equal for ENVI,ArcMap,GRASS,QGIS and 1 with the
GRASS plugin in QGIS.
It's very strange!Because the image is the same and, theorically, GRASS and
the GRASS plugin in QGIS are the same!!
Have you got my same problem?What do you suggest for fix it?
Thanks in advance!

Solimyr

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2

On Wed, Sep 14, 2011 at 1:52 PM, Solimyr <giannicristian@msn.com> wrote:

If I
open a satellite image with ENVI, ArcMap, GRASS,QGIS I get the same values
of the pixel of the image, but if I open it with the GRASS plugin in QGIS, I
get different values for the same pixel!

Did you set the computational region to the raster map before running the
query? That's the most likely source of user error...

Markus

3

I think yes!When I have created the location and the mapset, instead when put
myself the coordinates (e.g. WGS84 UTM Zone 30) I have set that using the
GeoTiff image!So when I open the same GeoTiff image, I get the image with
red boundaries around that!!

Is it sounds correct?Or I need to set something else?

Thanks,

Solimyr

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4

On Thu, Sep 15, 2011 at 7:43 AM, Solimyr <giannicristian@msn.com> wrote:

I think yes!When I have created the location and the mapset, instead when put
myself the coordinates (e.g. WGS84 UTM Zone 30) I have set that using the
GeoTiff image!So when I open the same GeoTiff image, I get the image with
red boundaries around that!!

Is it sounds correct?Or I need to set something else?

Essentially you need to set the region to the map. This is done with

g.region rast=your_raster_map [-p]

Markus

5

Thanks for the answer!!!I've done this but nothing change....Well, change
that now the red boundaries are closest to the area. Before I've set the
area biggest than my raster (but my raster was included).

Now, I'm thinking to try to threshold my raster using GRASS and using GRASS
plugin in QGIS and see the difference...But I can't find a tools that do
that in GRASS. Do you know if exist?

There is also a function that will show me the stats of the histogram in
GRASS?

Thanks,
Solimyr

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