[GRASS-user] [GRASSLIST:1116] Re: layers in vector datasets

[David Finlayson]

On 6/18/06, M S <mseibel at gmail.com> wrote:

>  so you have layers that can be linked to various tables.

Yes, you are correct. Only in GRASS the world "layer" is (confusingly)
used to refer to linkage (relation) between the vector map and the
attribute table. So, translating your statement above into GRASS. You
can have one vector map linked via  "layers" to multiple attribute
tables.

> if one does a
> v.patch command and now has two "layers" of lines, how can they both be put
> on the same layer, or does that not even matter?

I think all that means is that you have two attribute tables joined to
your single line vector.


> i guess its like if you
> have a polygon coverage in workstation.  then u can build it for lines (the
> .aat) and polygons (the .pat).  then u can add attributes and manipulate
> them for the different attribute tables.  however, since u cant have various
> "layers" of the same datatype in a coverage, i think that is where i get
> confused.

In my opinion that is a mis-feature (having different attribute tables
for boundary lines and areas), but I think you can do it in GRASS too
if you want.

>
>  in trying to run this v.net.steiner, i have lines on seperate layers.  not
> sure if that is throwing the fucntion for a loop because you have to specify
> the layer of arcs.

I can't help you with this. I haven't used the tool.

-- 
David Finlayson