[GRASS-user] Importing polygon maps with overlapping features

[Maris Nartiss]

Hello,
GRASS vector model is advanced, but sometimes it fails for simple
usage. It's one of best features is also it's point of failure.
Vector areas support in GRASS is built around bogous assumption, that
areas can not overlap. Such assumption holds true for many vector
usages (i.e. property boundaries don't overlap), but fails for other
vector usage patterns.
Let's assume one GRASS user wants to create vector area map with
suitable animal habitat areas. Does gay wolf and brown bear habitat
areas may overlap in real world? Yes they can. Can they overlap in
GRASS? No. User is forced to adapt semantics (habitat area) to data
storage limitations (one map per species).

Probably this is not the best example, simply I could not make better one fast.

Sorry for language and trolling,
Maris.

2009/1/7, Benjamin Ducke <benjamin.ducke at oxfordarch.co.uk>:

>
> The only trouble this gives me in practice arises when I need to
> import data created in non-topological GIS (e.g. ArcView Shapefiles)
> that contains overlapping polygons. Granted, those should not exist
> in the first place, but bad data quality and faulty topology is a
> constant reality in my field of work. With overlapping polygons,
> centroids cannot always be related to exactly one polygon, so the
> topology building fails for those cases and attribute data does
> not get attached "correctly".
>

> Cheers,
>
> Ben
>
>