[QGIS-Developer] lack of conflation tools

[Roger Merritt]

Hi Sylvain, Vincent, everyone.

Geospatial Conflation (as defined in the presentation included) has been my
life's work. In Australia, we call it 'Spatial Upgrades', conflation is to
my understanding just the transfer of attributes from an old theme (e.g.
roads) to a new theme.

The change in coordinates (based on shift vectors) can be done by
algorithms such as Rubber Sheeting, Best Guess (weighted mean averages with
some smarts), Iterative Best Guess (iteratively looking for problems and
adjusting), Least Squares, and is some cases, post processing to apply some
business rules to hold certain geometric shapes fairly constant.

The approach here is to do the Spatial Upgrade, detect where the upgraded
theme does not fit the destination, and either edit the Shift Vectors and
readjust, or carry on with manual edits.

I had an opportunity to rewrite it into a simple Windows Desktop app (from
a client/server (REST)) and consolidate all the good bits into it. It took
2 years including 5 major projects, so maybe 1.5 years of coding and
testing.

I started with QGIS Plugins last October, a lot to learn, but I have a
"Rubber Sheeting" plugin uploaded in the QGIS Repository. Have a look.

I have the issue that I estimate maybe 3-5 years to rebuild from Visual
Basic Desktop to Python Plugin, and am not prepared to do 5 years work for
no income. I would love to make it financially viable somehow, but have yet
to determine how to make it so.

I am also hoping to launch a website soon where you can trial/buy the
Windows Desktop App. Happy to let you know when that happens.

So, all up, I am hoping to claim this space in the QGIS World, but it is a
lot of work even if one knows all about it.

Regards
Roger


On Fri, May 31, 2024 at 5:32 PM Vincent Picavet via QGIS-Developer <
qgis-developer at lists.osgeo.org> wrote:

> Hi,
>
> Geospatial data conflation is not an easy task, and usually depends on :
>
> - the input data
>
> - desired output
>
> - semantics
>
> - conflation based mainly on semantics( / attribute data ), topology or
> purely geometric
>
> Note that semantic and topology-based methods are much more robusts than
> geometry-based ones.
>
> In any case, there is no magic workflow and the method has to be adapted
> to the specific context.
>
> I contributed to an implementation based on PostGIS quite a long time ago
> :
>
>
> https://docplayer.fr/8718145-Appariement-de-graphes-de-reseau-avec-postgis.html
> ( in french ).
>
> There could be some generic algorithms which could be made available in
> QGIS processing to ease creation of workflows for conflation ( e.g. node
> fingerprints, geometry local correspondance search  ).
>
> Get in touch if you are interested in developing some.
>
> Vincent
>
>
> On 30/05/2024 11:46, PIERRE Sylvain via QGIS-Developer wrote:
>
> Hi devs and  qgis power users,
>
>
>
> After investigating I can arg that there’s a lack of conflation tools in
> QGIS like such existing for Esri  :
>
>
>
>
> https://proceedings.esri.com/library/userconf/proc17/tech-workshops/tw_513-105.pdf
>
>
>
>
>
> Is there some plan or something I miss for doing such task in QGIS ?
>
>
>
> Thanks
>
>
>
>
>
> Sylvain PIERRE
>
> Chef de projet système d’information
>
> Direction des Systèmes d’Information et du Développement Numérique
>
> Service Projets et Ingénierie Numérique
>
> *Collectivité européenne d’Alsace*
>
> Tél : 03 88 76 68 88
>
> sylvain.pierre at alsace.eu
>
> www.alsace.eu
>
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>
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