[GRASS-user] attempt to define a smaller region

I'm a beginner with GRASS, running newest version 7.0.2 on Ubuntu Linux
14.04.

I'm attempting to create a new smaller region, and change the resolution to
something slightly larger. For some reason the map I get in the GUI display
window is very detailed however when I try to set a new region using
g.region it tells me that there is no detail to do it.

Apologies for all of the detail.

- This is working with raster maps from the UK ordinance survey (OS) system
- Originally downloaded four individual raster maps from OS is a sort of
.asc format
- Then converted them to ARCGIS format using ARCGIS
- Then combined them into one raster using mosiac to raster, then converted
back to .asc
- I've now imported the .asc raster into GRASS and it looks fine, lots of
detail but I want try to do some hydrologic modelling using TOPMODEL so need
to produce and topidx file, but before that I want to get a smaller region
-when I attempt to get a smaller region using g.region I get an invalid
input error.
-when I look at the raster info using g.region -p, there is almost no
information

(Mon Dec 14 11:36:09 2015)
g.region -p
projection: 99 (Transverse Mercator)
zone: 0
datum: osgb36
ellipsoid: airy
north: 1
south: 0
west: 0
east: 1
nsres: 1
ewres: 1
rows: 1
cols: 1
cells: 1
(Mon Dec 14 11:36:09 2015) Command finished (0 sec)

Something doesn't add up, the information must be in the raster because I
can see it, any suggestions as to what I've done wrong or how to extract the
correct region using UK british national grid references?

Thanks for any suggestions pointing me in the right direction.

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jamaas wrote

I'm a beginner with GRASS, running newest version 7.0.2 on Ubuntu Linux
14.04.

I'm attempting to create a new smaller region, and change the resolution
to something slightly larger. For some reason the map I get in the GUI
display window is very detailed however when I try to set a new region
using g.region it tells me that there is no detail to do it.

Apologies for all of the detail.

- This is working with raster maps from the UK ordinance survey (OS)
system
- Originally downloaded four individual raster maps from OS is a sort of
.asc format
- Then converted them to ARCGIS format using ARCGIS
- Then combined them into one raster using mosiac to raster, then
converted back to .asc
- I've now imported the .asc raster into GRASS and it looks fine, lots of
detail but I want try to do some hydrologic modelling using TOPMODEL so
need to produce and topidx file, but before that I want to get a smaller
region
-when I attempt to get a smaller region using g.region I get an invalid
input error.
-when I look at the raster info using g.region -p, there is almost no
information

(Mon Dec 14 11:36:09 2015)
g.region -p
projection: 99 (Transverse Mercator)
zone: 0
datum: osgb36
ellipsoid: airy
north: 1
south: 0
west: 0
east: 1
nsres: 1
ewres: 1
rows: 1
cols: 1
cells: 1
(Mon Dec 14 11:36:09 2015) Command finished (0 sec)

Something doesn't add up, the information must be in the raster because I
can see it, any suggestions as to what I've done wrong or how to extract
the correct region using UK british national grid references?

Thanks for any suggestions pointing me in the right direction.

adjust the region to your raster, e.g.

g.region -a raster=elevation@PERMANENT align=elevation@PERMANENT
g.repion -p to show the region settings

then digitize a vector polygon for the region of your intereset, then do

g.region -a raster=elevation@PERMANENT vector=yourvector
align=elevation@PERMANENT

to shrink your region to the area of your interest

g.repion -p to show the region settings

HTH

-----
best regards
Helmut
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jamaas wrote

Apologies for all of the detail.

- This is working with raster maps from the UK ordinance survey (OS)
system
- Originally downloaded four individual raster maps from OS is a sort of
.asc format
- Then converted them to ARCGIS format using ARCGIS
- Then combined them into one raster using mosiac to raster, then
converted back to .asc

have a look at

gdalbuildvrt http://www.gdal.org/gdalbuildvrt.html
GDAL Virtual Format Tutorial http://www.gdal.org/gdal_vrttut.html

to build a virtual dataset with your several asc-files, no need to go
through A**G**-workflow.

-----
best regards
Helmut
--
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