[Talk-ca] [bot] Proposal to fix issue with duplicated inner polygons in Canada

[Daniel @jfd553]

Bonjour Pauline,
IMHO, this is a good initiative. OSM best practices have evolved with the community and keeping data as close as possible to current rules - when possible - is in everyone’s interest.
The current problem arises from a 2009 consensus made within the Canadian OSM community, which was later documented in the wiki [1] (look at the history). At that time, there were no such precise rules on the structure of data or on the procedure for importing data.
So, as long as the relevant codes of conduct are respected, I agree with the project.

Daniel

[1] https://wiki.openstreetmap.org/wiki/CanVec:_Geometric_Model

From: OSM [mailto:OSM at tomtom.com]
Sent: Thursday, December 02, 2021 04:44
To: talk-ca at openstreetmap.org
Subject: [Talk-ca] [bot] Proposal to fix issue with duplicated inner polygons in Canada


Hello everyone,
Bonjour à tous,

I'm Paulina from TomTom.

We would like to join your conversation and introduce our team to you.

You might have read about TomTom’s OSM activities in this weekly OSM overview<https://weeklyosm.eu/archives/14716>, or in our own blog posts (this one<https://www.tomtom.com/blog/maps/tomtom-openstreetmaps-mapmetrics-map-editing/> and this one<https://www.tomtom.com/blog/maps/the-battle-for-quality-maps/>). Our team is performing data analysis in OSM to identify issues worth fixing.

In Canada in particular, we've encountered an issue related to double inner polygons. The geometry of the multipolygon inner ring is duplicated: one is in a relation but without a tag and another has tags but is not part of the relation (Osmose Rule 1170 Class 1<http://osmose.openstreetmap.fr/en/issues/open?item=1170&source=&class=1&username=&bbox=> "Double inner polygon").

Following the Automated Edits code of conduct<https://wiki.openstreetmap.org/wiki/Automated_Edits_code_of_conduct>, we have developed a bot that would be useful in solving this issue. All details about it (explanation of the algorithm, examples, etc.) are described on the dedicated wiki page https://wiki.openstreetmap.org/wiki/Automated_edits/TTmechanicalupdates/Fix_issue_with_duplicated_inner_polygons_in_Canada.

Our internal analysis has shown that this problem is primarily caused by an import of CanVec data. According to the CanVec OSM wiki documentation<https://wiki.openstreetmap.org/wiki/CanVec#Issues_found_in_OSM>, the issue is already known by the community and mentioned there as "Duplicate land features". The bot is suitable for CanVec, but the double inner polygon issue appears in around 3,000 examples that do not have a source mentioned in their tags. For these issues, we would like your opinion about whether we should also fix them (please see the Discussion<https://wiki.openstreetmap.org/wiki/Automated_edits/TTmechanicalupdates/Fix_issue_with_duplicated_inner_polygons_in_Canada#Discussion> part in the wiki documentation).

It is worth mentioning that in the past, we've already gained experience with mechanical updates in OSM by running a bot to update night-time urban speed limits in Poland (see the proposal mentioned in this weeklyOSM summary<https://weeklyosm.eu/archives/14709>, and the forum thread<https://forum.openstreetmap.org/viewtopic.php?id=73116> about this action).

We propose to do a test run by updating invalid polygons in Southwestern Ontario, where 800 cases are logged by the Osmose rule.

Per the Automated Code of Conduct, we will wait for your feedback before we begin. We look forward to building and improving OSM together with you!

Kind regards,
Paulina.

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