[GRASSLIST:2657] v.patch (category IDs and descriptions) - supplement

[Christof Bigler]

I have some additional information (see my last posting):
When I convert the vector maps with v.to.rast to raster maps (map1.v to 
map1.r, map2.v to map2.r, map3.v to map3.r), I can see that the 
category descriptions of the grid cells from the original map2.v data 
in map3.r are overwritten with the descriptions of map1.v.

Any help is appreciated.

Christof

> From: Christof Bigler <christof.bigler at colorado.edu>
> Date: 16. Februar 2004 13:19:52 GMT-07:00
> To: Grasslist <GRASSLIST at baylor.edu>
> Subject: v.patch (category IDs and descriptions)
>
> I merged two vector maps with v.patch in=map1.v,map2.v out=map3.v
>
> map1.v has 988 categories, map2.v 362, and map3.v again 988 
> categories, apparently with the first 362 categories having the same 
> ID.
>
> v.report map1.v type=area:
> # | 	description | 	count
> 2	1			1
> 3	2			1
> 4	1			1
> 5	3			1
> ...
>
> v.report map2.v type=area:
> # |	description |	count
> 2	1			1
> 3	2			1
> 4	2			1
> 5	3			1
> ...
>
> v.report map3.v type=area:
> # | 	description | 	count
> 2	1			2
> 3	2			2
> 4	1			2
> 5	3			2
> ...
>
> This is quite confusing for new Grass users. It looks, as if there are 
> non-unique category IDs in map3.v. And it looks that in map3.v the 
> category descriptions of map2.v are overwritten by category 
> descriptions of map1.v.
>
> But since Grass uses an internal ID, I assume that the category 
> descriptions of map2.v are (internally) not overwritten.
>
> Can anybody enlighten me?
>
> Christof
>
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