[postgis-users] DE-9IM question

[Stefan Keller]

Hi fork

On 2012/5/8 fork <forkandwait at gmail.com> wrote:
> Does anyone know of an exhaustive reference of DE-9IM matrices, with pictures?

I don't think I would call it a reference but take a look
http://labs.geometa.info/postgisterminal/?xapi=node[tourism=zoo] :
There is a menu item "Relate exemplified (bool)" which displays
parameters as as list of pictures (disregarding of the current query).
Choose the two geometry types and the DE-9IM pattern, then click on
"[+]" and look at the prerendered pictures.
Pls. give feedback if you have any suggestions.

-S.


> Context:
>
> I just finished classifying a bunch of polygons based on their relationship to
> enveloping poly's in another layer (census blocks and census city boundaries,
> respectively).  The regular old st_within() and friends weren't enough, so I
> calculated all the DE-9IM's, counted them (yay for GROUP BY and real
> databases!), and made sure I knew what was going on for each of the matrices
> returned (7 total).  Then I classified my block polys based on the strings.
>
> I found it CRAZY how many different types of DE-9IM's could be returned, even
> with just polygons and very well aligned boundaries (credit to the US Census
> Bureau's geography division).  Only a few of the matrices in my data were
> actually described in the few docs I could find.  Besides the seven in my data,
> there are at least four more that can be generated by various combinations of
> overlapping polygons.
>
> It would have been much easier to do this project if I had been able to
> reference a list of possibilities along with pictures.  It would be even better
> if I could be confident that such a list was exhaustive.
>
> Does anyone have a reference?
>
> If not, I could continue to work on an atlas of DE-9IM matrices, at least for
> polygons, and submit it somewhere if it were helpful.  Any ideas for where that
> might go? (I don't have a blog and don't want to start one).  Maybe just the
> wikipedia entry?
>
> For those who don't know, a DE-9IM matrix is the output of st_relate(geo1,
> geo2), and there is an excellent intro in the docs.  Fascinating stuff really.
>
> Tx
>
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