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Has anyone thought about the Arc/Info coverage model? The idea would
be to have a table with line geometries and attributes reflecting the
left and right polygon ids. My thought is you do your edits on the
line geometry table and then polygon topology is built in a separate
(dependent, inherited??) table based on the line table using well
defined procedures. The only function I don't see offhand that is not
there is a split polygon with line. Just my thoughts.<br>
<br>
Bruce Rindahl<br>
<br>
Webb Sprague wrote:
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cite="mid:b11ea23c0805151038oc5c1282t37e0fe7cb6b7c2e3@mail.gmail.com"
type="cite">
<pre wrap="">On Thu, May 15, 2008 at 5:20 AM, George Silva <a class="moz-txt-link-rfc2396E" href="mailto:georger.silva@gmail.com"><georger.silva@gmail.com></a> wrote:
</pre>
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<pre wrap="">Hello all again,
I´m curious. I´ve said in qgis list and some other 'desktop' GIS software
lists that the biggest feature missing for OSGIS is something like the
'auto-complete' polygon in ArcGIS,, that would make life much easier.
</pre>
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<pre wrap=""><!---->
Indeed!
</pre>
<blockquote type="cite">
<pre wrap="">I´ve been reading some things, and i´ve seem people mentioning trigger based
topology (eg cut out the overlaping area of digitized polygons, or,maintain
only the overlaping areas of the digitized polygons, and other related
issues).
</pre>
</blockquote>
<pre wrap=""><!---->
I think the hard part is deciding how you want to do this exactly,
since all approaches involve changing the data somehow; a lot of
people are chary of automatically deleting gaps, for example, lest
they aren't really gaps (consider the Vatican Republic in a map of
euro nations...).
</pre>
<blockquote type="cite">
<pre wrap="">I imagine that would be a trigger using something like after insert update
the_geom.
Can you guys with more experience give me a example, so i can build my own?
Best pratices? Some light around this subject?
</pre>
</blockquote>
<pre wrap=""><!---->
Have you ever written a non-geo trigger in postgresql? If not, I
would practice using the docs; I am pretty sure you could just modify
NEW with a geo operator/ function.
If so, I think a larger scale project needs to be embarked on. The
work so far seems to me to be quite low level without a grand plan,
and I think a grand plan is needed. I would start with a bunch of
functions for modifying a geometry based on its neighbors and some
topology constraints, then maybe a schema to store topology
information, and only then start implementing triggers. But this is
armchair quarterbacking--hopefully someone with some real experience
will say something...
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