Hi Markus,<br>I possibly don't have a full understanding of what topology is. I thought it was more or less the geometry, with a few rules relating different objects to each other. Attributes are things like place names or a value at a location, within a boundary etc. As postgis allows the storage of geometries then isn't this the topology? I've not had much luck with grass getting it to recognise things like shared boundaries (so I only have to digitise them once) apart from using the snap to vertice feature (though as postgis seems the most useful at the moment I'm concentrating on that).<br>
<br>Thanks<br>Matt<br><br><br><br><div class="gmail_quote">On Tue, Dec 2, 2008 at 7:45 PM, Markus Neteler <span dir="ltr"><<a href="mailto:neteler@osgeo.org">neteler@osgeo.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Matt,<br>
<div class="Ih2E3d"><br>
On Tue, Dec 2, 2008 at 4:31 AM, Matt B <<a href="mailto:mattslists@gmail.com">mattslists@gmail.com</a>> wrote:<br>
> Hi Group,<br>
> I'd like to set up grass to edit / work with data in a postgis database. So<br>
> far I've figured out (and been informed, thanks Richard) that grass stores<br>
> the topologoly data in it's own database and the external database is just<br>
> used for attributes.<br>
<br>
</div>GRASS stores per default all data (geometry + attributes) in its own format<br>
(i.e., attributes in a DBF file in GRASS 6 and in SQLite in GRASS 7).<br>
<br>
Optionally attributes can be stored in PostgreSQL (not PostGIS), Mysql,<br>
SQLite, and ODBC.<br>
<div class="Ih2E3d"><br>
> Is there a way to have grass store the topology data in<br>
> postgis so I can easily work with the data in different applications?<br>
<br>
</div>Yes, using v.external. But note that this is a read-only connection.<br>
We hope that in future this will be read-write.<br>
<br>
The issue behind this is that GRASS is a topological GIS while<br>
PostGIS is Simple Features (no topology per default). So there<br>
is a "conversion" needed between these two worlds.<br>
<font color="#888888"><br>
Markus<br>
</font></blockquote></div><br>