[GRASS-user] creating new geometry from pre-existing lines and points

[Maris Nartiss]

I'm sorry to interrupt Your advanced discussion, but if there are just
some "holes" that are required to be converted to polygons, then why
not use v.digit? Simply digitising new centroid inside a hole
(enclosed from other polygon boundaries) will turn hole into polygon.

WBR,
Maris.

2008/1/31, Nikos Alexandris <nikos.alexandris at felis.uni-freiburg.de>:
> Hi!
>
> On Wed, 2008-01-30 at 23:52 +0200, David Epstein wrote:
> > Hi Nikos,
> >
> > Thank you for that suggestion. Indeed, I did NOT realize that v.extract
> > was used to create new geometry in a layer. However, I too need some of
> > the islands (is there a technical difference between island, hole, and
> > missing polygon?).
>
> I am not sure!
>
> Would be nice to have a kind of GRASS-GIS lexicon with (basic and
> non-basic) definitions!
>
> * island... I suppose are small poylgons within larger ones
>
> * holes... just "nothing" within larger polygons
>
> * missing polygon... ?
>
> >
> > There is a single missing polygon that I now have attribute data for and
> > I want to create the polygon (from the existing points and lines) and
> > fill-in the related attribute fields.
> >
> > I imagined some sort of interactive process of clicking on the relevant
> > bounding elements and *presto* the polygon would jump into existence. I
> > tried this in v.digit but was not able to get the desired result.
>
> If you just need to quickly correct a small number of polygons try with
> the "fresh-baked" QGIS (r0.9.2.rc1), which works as a GRASS frontend.
>
> 1. you need to add in your /etc/apt/sources.list following source:
> deb http://ppa.launchpad.net/timlinux/ubuntu gutsy main
>
> 2. sudo aptitude update && sudo aptitude upgrade
>
> --- if not already installed... "sudo apt-get install qgis
> qgis-plugin-grass"---
>
> 3. Load GRASS plugin
>
> 4. Open your GRASS mapset within QGIS
>
> 5. Load your vector (polygon) file
>
> 6. Play with the tools... ( I have seen the new digitising tools... must
> be really what you are looking for!) and edit your polygons.
>
> *** You need first to "right click" on your vector layer and "save as
> shapefile" -- Then you can edit.
>
>
>
> >
> > This is a really basic step that people do several times a day, right?
> >
> > -david
>