[GRASS-user] vector maps - help needed - part 2

[Maciek Sieczka]

On Tue, 30 May 2006 22:10:42 +0200
Wolfgang <wollez at gmx.net> wrote:

> Hi all,
> 
> sorry, but I still don't understand the vector/database handling of 
> grass completely. At the moment I use dbf files, but this seems not
> to be very flexible. It seems also that not all vector data is stored
> in the dbf files.

Only attributes of vector features (point,line,centroid etc.) are
stored in the table (no matter what DB backend in Grass).

Note that a feature to have an entry in the table has got to have a
category first (see v.category).

> When I import for example a shapefile into grass,
> are all nodes of the lines imported to dbf?

No. One line is one, whole vector feature. If you need each node to have
separate table entry, use v.to.points -v, then v.to.db.

> I think no because I have
> an other folder on my computer which is called "vector" but what are
> the files "cidx,coor,dvln,head,hist,topo"?
> 
> As you can see, I'm really confused, what this database stuff is  for 
> when all data is still stored somewhere else.
> 
> I hope that somebody can help me and explain me the idea of 
> vector/database handling.

v.in.ogr, as well as many other Grass modules that output a new vector
layer, will setup categories for features and upload them into a key
"CAT" column (it could be any other name though, see v.db.connect)
along with their attributes respectively.

Read your grass-6.1.cvs/docs/html/vectorintro.html too.

I hope it helps.

Best,
Maciek

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