[GRASS-user] Newbie question on g.region

[Michael Barton]

The new GRASS 6.1 startup has an option to create a location from a
georeferenced map. 

If you already have a location (i.e., projection) set up and something in
it, but are having region issues, you can use g.region to set the region of
interest to match the map you have

G.region rast=[mapname]

This will set up the region properly to match the resolution and extents of
your map.

I should also point out that NED are derived from topo contour lines and
often have poorly interpolated topography, such that they have a step-like
quality. I'd recommend using the 30m SRTM's instead. I haven't had trouble
with r.los, but r.cva is a much more versatile tool. It's only drawback is
it's EXTREME slowness when doing multiple viewsheds.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton



> From: Hamish <hamish_nospam at yahoo.com>
> Date: Fri, 9 Jun 2006 21:24:47 +1200
> To: gary <lists at lazygranch.com>
> Cc: <grassuser at grass.itc.it>
> Subject: Re: [GRASS-user] Newbie question on g.region
> 
>> My ultimate goal for GRASS is to do viewshed analysis with r.los. I
>> have downloaded NED files from the USGS seamless website. I have also
>> managed to convert the .adf file to geotiff using gdal_translate.
> 
> Can't you download NED data directly as GeoTIFF?
> 
> 
> Some hints:
> 
> r.los doesn't scale well at all. Download "r.cva" (install with GRASS GEM?)
> and use that instead if you can.
> 
> Also see hints on r.sun and r.sunmask page.
> 
>> My problem concerns starting up GRASS. When I try to run r.in.gdal, I
>> get an error message regarding the default region is not set. I gather
>> I'm not initializing GRASS properly.
> 
> g.setproj ?
> 
> g.region -p ?
> 
> r.in.gdal -o ?
> 
> 
> 
> good luck,
> Hamish
> 
>