[GRASS5] One more thing related to layers

[Radim Blazek]

On 3/12/06, Trevor Wiens <twiens at interbaun.com> wrote:
> I'm starting to think about who to update the layers documentation. I
> know that every geometry object within in one layer can have one or
> more categories. Can it also have none?

Yes. For example boundaries usually dont have a category.

> To use the forest / lake
> example. Is it possible to have a lake virtual layer in which only
> lakes will appear and forest virtual layer in which only forests
> appear? AFAICT this would require having some geometry objects having
> no CAT values in the corresponding layers where they shouldn't be
> visible. Is this correct?

In the forest layer appeare only forests and and in lake layer only lakes.
No need/impossible to use objects without category. If you add an object
without a category it will not appeare in any layer.

Radim

> T
> --
> Trevor Wiens
> twiens at interbaun.com
>
> The significant problems that we face cannot be solved at the same
> level of thinking we were at when we created them.
> (Albert Einstein)
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