[GRASS-user] Newbie question on g.region

[gary]

http://seamless.usgs.gov/website/seamless/products/srtm1arc.asp

The link above indicates the 30m SRTMs are 1 arcsecond resolution. While 
I am going to first use the 1 arcsecond NED, there are 1/3 arcsecond 
NEDs available. Would the 30m  SRTMs be superior to a 1/3 arcsecond NED?

Michael Barton wrote:
> 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
>>
>>
> 
> 
> 
>