MASK for a hand drawn area

[Susan Huse]

> From grass-lists-owner at max.cecer.army.mil Mon Oct 11 07:46:22 1993
> Date: Mon, 11 Oct 1993 14:38:13 GMT
> From: news at yuma.ACNS.ColoState.EDU (News Account)
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> Newsgroups: info.grass.user
> Path: copeland
> From: copeland at lamar.ColoState.EDU (Jeffrey Copeland)
> Subject: MASKS
> Sender: news at yuma.ACNS.ColoState.EDU (News Account)
> Message-ID: <Oct11.143811.18889 at yuma.ACNS.ColoState.EDU>
> Date: Mon, 11 Oct 1993 14:38:11 GMT
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> Organization: Colorado State University
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> 
> I'm trying to create a MASK for a hand drawn area.  I can see how to
> take a vector area and get a raster file from that, but how do I get
> the raster file to have 2 categories, 1 inside mask line and the other
> outside.  
> 
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> 
Assuming that you created the vector file and converted to raster correctly,
r.mask should work just fine. 
In r.mask create a new mask.  To each category that you wish to stay 
"visible" give a value of one.  To all categories you wish to disappear 
give a value of 0.  
It doesn't really matter how many categories the raster file has that you
use to mask.  The MASK will have only two visible (included in the mask) 
and invisible (not included in the mask).