[Talk-ca] Re : Coastline rendering in Quebec

[James A. Treacy]

On Sun, Jun 10, 2012 at 08:47:35PM +0100, Pierre Béland wrote:
> The principal problem with the relation was that the riverbank polygon has been broken. I finally corrected St-Laurent-Mtl Relation and issued a few dirty tiles requests. It now results that the islands are rendered properly. But you may still notice some problems at various zoom levels. In these cases, you just have to issue dirty tiles requests.

I took a look at one of the islands and noticed that there are both a
coastline and riverbank defining the outline of the island. Does the
riverbank way provide any tangible benefit? Personally, I dislike this
type of duplication as it more than doubles the chance of problems.

We really should have a set of best practices on the wiki for
coastlines. Note that coastline includes major waterways, e.g. St.
Lawrence River, and the great lakes.

> View relation        http://www.openstreetmap.org/browse/relation/1775822
> View Changeset    http://www.openstreetmap.org/browse/changeset/11858120
> 
> 
> I finally found that the polygon was broken at the exit of Riviere des Prairies. I also fixed the relation Riviere des Prairies C
> View relation        http://www.openstreetmap.org/browse/relation/1769788
> 
> I also looked at the various islands and found inconsistancies and missing islands. I corrected natural=land for natural=coastline and added the islands wich where not part of the relation.
> 
> It is not easy to validate such a relation with many riverbank sections and islands (107 members). I may have missed other problems. It would be good that others validate to assure that everything is ok.
> 
> Be carefull when you edit such relations or ways related to these relations. If you send your data to the server and the polygon is 
> broken, a Warning message will be issued. In this case it is important 
> to fix it otherwise we will encounter rendering problems.
> 
> When you edit such relations and are not sure about how to treat islands, riverbanks and coastlines relations, please send an email to the list to let others look at it.  
>   
> 
> Pierre 
> 
> 
> 
> >________________________________
> > De : Pierre Béland <infosbelas-gps at yahoo.fr>
> >À : Talk-CA OpenStreetMap <Talk-ca at openstreetmap.org> 
> >Envoyé le : Vendredi 8 juin 2012 14h25
> >Objet : [Talk-ca] Re :  Coastline rendering in Quebec
> > 
> >
> >I looked in detail at Boucherville islands and cannot find explanations for this rendering problem. There are other islands down the Saint-Laurent river and Richelieu river with the same rendering problem.  I issued /dirty tiles requests but this did not fix the problem.
> >
> >
> >I removed a wetland from the coastline relation.
> >wetland http://www.openstreetmap.org/?way=77938080
> >St-Laurent-Mtl Relation http://www.openstreetmap.org/browse/relation/1775822
> >
> >
> >
> >Pierre 
> >
> >
> >
> >>________________________________
> >> De : Harald Kliems <kliems at gmail.com>
> >>À : talk at openstreetmap.org 
> >>Cc : Talk-CA OpenStreetMap <Talk-ca at openstreetmap.org> 
> >>Envoyé le : Jeudi 7 juin 2012 8h10
> >>Objet : [Talk-ca] Coastline rendering in Quebec
> >> 
> >>On the talk-ca list there have been a few discussion about problems
> >>with "flooded" areas in southern Quebec. The conclusion seems to be
> >>that the problems are due to the rendering of the coastline which only
> >>gets updated every once in a while. The two
>  cases are:
> >>
> >>* http://www.openstreetmap.org/?lat=45.6101&lon=-73.4411&zoom=13&layers=M
> >>This problem is comparatively recent. Current data appears to be
> >>correct. Problem is visible on zoom>=13
> >>
> >>* http://www.openstreetmap.org/?lat=45.342&lon=-74.24&zoom=9&layers=M
> >>This one has been around for at least 6 months. Current data appears
> >>to be correct. Problem is visible on zoom>=9
> >>
> >>We haven't been able to figure out who to contact about these issues.
> >>Can anyone point us in the right direction?
> >>
> >>Thanks,
> >>Harald.
> >>

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-- 
James (Jay) Treacy
treacy at debian.org