[GRASSLIST:7716] Re: Raster Resolution (help requested)

[Michael Barton]

Dave,

Change the resolution using g.region (also in GUI).

Set the resolution to what you want using g.region, THEN run v.surf.rst. It
will interpolate to the resolution set using g.region. In other words, if
you do ...

G.region res=1

...it will set your resolution to 1 degree (for your latlon map). V.surf.rst
would then create 1 degree x 1 degree raster cells.

G.region res=.00001

...would create a much higher resolution map--with many more cells of
course.

It may be that your original DEM already has a sufficiently high resolution
and you just can't see it. To make your region resolution match that of your
DEM, use...

G.region rast=[myDEM]

...(where [myDEM] is the name of your raster DEM map)

Using g.region, GRASS can set not only the zoom window (extents), but also
the visible and analytical resolution on the fly. You must remember that
nearly all raster operations take place ONLY in the window set by g.region
and at the resolution set by g.region. However, this can be VERY useful.

Michael


On 7/25/05 11:55 AM, "Dave Sampson" <gis at watersheds.ca> wrote:

> Hey yall,
> 
> In the past I have worked mainly with RASTER layers in GRASS and they
> just worked (some how). Now I am working alot with vectors in GRASS. For
> instance I have a region that was created througha v.in.ogr. Now when I
> bring in the coresponding raster maps they are verry blocky unless I
> view them from a far out zoom. My region settings are
> 
> projection: 0 (x,y)
> zone:       0
> north:      44.86371257
> south:      44.67956501
> west:       -76.34802196
> east:       -76.08834984
> nsres:      0.00920738
> ewres:      0.01298361
> rows:       20
> cols:       20
> 
> I created a DEM from contour lines (v.surf.rst) and the results are
> undesireable due to the chopyness of the raster. for instance instead of
> smooth DEM I have lakes that contain one or two raster cells. The same
> area would contain MANY contour lines. Cheers
> 
> A quick explanantion of what I've done and how to increase the
> resolution of the rasters in my project would be appreciated.

____________________
C. Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
PO Box 872402
Arizona State University
Tempe, AZ  85287-2402
USA

Phone: 480-965-6262
Fax: 480-965-7671
www: <www.public.asu.edu/~cmbarton>