[postgis-users] Well done with GEOS & QGIS!!!

[Brent Wood]

--- Martin Davis <mbdavis at refractions.net> wrote:

> Thanks, Brent (for pieces which apply to me....  8^)
> 
> And if you use JUMP you can use it to perform the isValid test as well  
> (it's built on essentially the same codebase as GEOS)  8^)

I have used JUMP, but not for some time. I found it's memory management for
layers with millions of features was a problem, I guess more a JAVA problem
than JUMP problem. QGIS might take a few minutes to retrieve & render the data,
but it gets there.

& then I have a QGIS developer (C++ programmer) just down the hall, & no JAVA
developers around at all :-)

Note that I can do isValid in QGIS (sort of) in the where clause which QGIS
passes to PostGIS. 

It's great to have the choices though. I had a sea-ice dataset for the Ross Sea
(Antarctica) which I used JUMP to show in a presentation, as QGIS (then) did
not support transparency, & overlaying transparent weekly layers was a very
effective way to illustrate the regions which remained clear in each season. 

An animation gave the sense of ice movement better, but did not give the
overall view showing the clear seaways (which were suitable for fishing)
throughout the season.


So thanks again for your contribution!

Brent


> 
> Martin
> 
> Brent Wood wrote:
> > Instead of asking for help or features, just for a change I figured I'd
> pass on
> > some thanks for something working perfectly (touch wood, fingers
> crossed....
> > :-)
> >
> > I just ran difference() & got a GEOS error:
> > NOTICE:  TopologyException: found non-noded intersection between 173.56
> > -35.3436, 173.558 -35.3364 and 173.56 -35.3412, 173.557 -35.3388 173.559
> > -35.3407
> > ERROR:  GEOS difference() threw an error!
> >
> > It sort of made sense, & suggested there was a topology error in my
> polygon.
> > I ran isvalid() & got a false on the very polygon I was using in
> difference,
> > along with the message:
> > NOTICE:  Self-intersection at or near point 173.559 -35.3407
> >
> > Wow!!! All I needed to know! 
> >
> > Opened it up in QGIS, zoomed in & there it was, make it editable, drag some
> > vertices around to fix the error, save it, re-run the SQL & it worked
> > perfectly.
> >
> > Fantastic to see this level of useability, interoperability  & topology
> support
> > coming out of these tools.
> >
> >
> > Kudos to all you developers out there!!!
> >
> >
> > Cheers,
> >
> >   Brent Wood 
> >
> >
> >
> >
> >
> > _______________________________________________
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> > postgis-users at postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
> >
> >   
> 
> -- 
> Martin Davis
> Senior Technical Architect
> Refractions Research, Inc.
> (250) 383-3022
> 
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