[GRASS-user] working with vectors

[Moritz Lennert]

On 15/05/09 12:23, achim wrote:
> Hello folks,
> 
> I wonder, how you deal with vector-data. I am really not happy with it,
> even with help from qgis. Do I have to go deep into PostGis (which does
> not support topology, as far as I know) to make some more or less
> advanced working steps like selecting areas,  which intersect with
> another, 

v.select. In grass 6.x it only provides the option "overlap", but in 
grass7, you get the full GEOS set, i.e.: equals, disjoint, intersects, 
touches, crosses, within, contains, overlaps, relates.

> combine line vector layers and break on intersections

v.patch + v.clean

>, measure
> length of lines even in an latlong projection...

v.to.db, although I'm not 100% sure how that deals with lat-long. Only 
comment in the man page:

"When calculating perimeters in Latitude-Longitude locations, the 
geodesic distance between the vertices is used."

I would suppose that this is the same for line length...

> Any hints for dealing with vector data in fossgis are welcome.

You have tons of options. GRASS has a very advanced vector engine and 
you should be able to do most of what you need, once you get used to it.
Start by reading this:

http://grass.itc.it/grass64/manuals/html64_user/vectorintro.html

Moritz