[GRASSLIST:2845] Re: Need instuctions?

Eric G. Miller egm2 at jps.net
Thu Jan 3 09:14:02 EST 2002

On Thu, 3 Jan 2002 08:28:23 -0500 , "Kidd, James P." <james.kidd at Covance.Com> wrote:

> Hello:
> I have been a reader of the grass list for a few weeks.  I need some
> instructions on how to read in some dem files that I converted from sdts
> format.  I am trying to build a county database using a number of different
> file formats, but have run into some difficulty with the dems.

Converted to what?  Note: the r.in.gdal importer can handle SDTS DEM's
directly.  Think you give it the CATD file...

> I guess my first question is:  Is this the right list to submit help
> questions?


> I normally use ArcView 8.1 on the NT side of life and find that while I can
> read in the dems into it, I can not merge them.  I don't have access to
> ArcInfo so I am looking to GRASS for the solution.
> Does anyone know how to do this?  I kinda need step by step instructions
> since the help files seem to say it can be done, but don't really spell out
> how to do it.

Well, first you need to import the DEM's ;-).  Then look at r.patch and
possibly r.fillnulls.  Merging DEM's is not always straight forward for
the simple reason that they don't always edge match that well, or the
elevations simply don't agree.  Anyway, if the data matches up well, it
should be a pretty simple process.  Be aware, that the GRASS "region"
setting will almost always affect the extents and resolution of raster
operations.  This often trips up people not familiar with GRASS.

GRASS ~/> r.patch input=dem1,dem2,dem3 output=dems_123

Eric G. Miller <egm2 at jps.net>

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