[Talk-ca] Missing harbours and marshes - L Ontario

[Adam Dunn]

I've done a cursory examination of the Oshawa Harbour, and it would
appear that there are two ways defining the water's edge:
1.) a PGS Coastline import, which is tagged as natural=coastline,
2.) a Canvec import, which is tagged as natural=water, and is part of
a multipolygon relation, tagged with natural=water.

OpenCycleMaps and OSMA are rendering the newer (and possibly more
accurate) Canvec version, whereas Mapnik is rendering the older PGS
way. This goes contrary to what I have seen, as usually natural=water
ways and relations will get rendered as long as they are outside a
natural=coastline. You could think of it as coastline being given a
higher priority than water, or you could think of it as starting with
a default of land, then water getting rendered first, then coastline
gets rendered last (if your natural=water has a hole for an island,
but natural=coastline doesn't, then the island will get painted over
with blue). So what I'm seeing Mapnik render doesn't match up with
what I would expect based on the raw data local to that area (but what
Mapnik has done globally makes sense, see next paragraph).
There are some problems with the data:
The Canvec natural=water way is not closed. This breaks the rules of
natural=water (should always be closed), so Mapnik will probably toss
the rendering of the way into the rubbish bin. The process to have
large natural=water without closing each individual way is to have a
relation. The relation for the Canvec-based Lake Ontario also happens
to be open, so Mapnik would probably toss that as well. I don't know
who or when this open polygon was edited, but I'm guessing it's the
problem, and if you were to close it, Mapnik should get better.

Eventually the PGS coastline will go away and Canvec will replace it
with either natural=water relation or natural=coastline. I think it's
okay to have both temporarily (it's what I'm doing right now up in
Great Slave Lake), but PGS should eventually be deleted.

TL;DR:
Weait is correct that it's a relation problem, but he's wrong that
it's a matter of patience to see a new render.

Adam

On Thu, Aug 18, 2011 at 2:42 PM, Bob Dustan <bob.dustan at gmail.com> wrote:
> The Cycle Map and Osmarender views in OSM show older views of the affected
> areas (prior to change).  (at least, they do right now)
>
> Bob
>
>
> On 08/18/2011 04:50 PM, Gordon Dewis wrote:
>
> I looked at Oshawa Harbour and it seems to be there. The most recent
> changeset for that area seems to be #9033032
> (http://www.openstreetmap.org/browse/changeset/9033032) but not knowing what
> it looked like before I can't really say if this is the culprit or if it's a
> matter of waiting for it to be rendered as Richard suggested.
>
>   --G
>
> On Thu, Aug 18, 2011 at 4:36 PM, Bob Dustan <bob.dustan at gmail.com> wrote:
>>
>> Oops, should have included that with my original posting.  Sorry.
>>
>> Here are a couple of examples:
>>
>> Bowmanville harbour (Port Darlington)
>> http://www.openstreetmap.org/?lat=43.89135&lon=-78.67463&zoom=15&layers=M
>>
>> Oshawa Harbour
>> http://www.openstreetmap.org/?lat=43.86733&lon=-78.82678&zoom=16&layers=M
>>
>> Newcastle (graham Creek and Wilmot Creek)
>> http://www.openstreetmap.org/?lat=43.89767&lon=-78.59155&zoom=15&layers=M
>>
>> Bob
>>
>>
>> On 08/18/2011 12:30 PM, Richard Weait wrote:
>> > On Thu, Aug 18, 2011 at 10:10 AM, Bob Dustan <bob.dustan at gmail.com>
>> > wrote:
>> >> I just noticed that several small bodies of water along the north shore
>> >> of Lake Ontario have disappeared (partially or completely).  Some
>> >> harbours affected are Oshawa, Bowmanville, Newcastle, Port Hope, and
>> >> Cobourg.  Some marshes (e.g. Westside Marsh near Bowmanville) are gone.
>> >> Some creek/river sections near the shore are gone as well.
>> >>
>> >> Can someone clarify what is happening with this?
>> > How about a link or two to the areas and any changesets you think
>> > might be involved?
>> >
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