[OSM-newbies] Why doesn't Mapnik play nice?

James Ewen jewen at shaw.ca
Sat Nov 8 16:43:17 GMT 2008


On Sat, Nov 8, 2008 at 3:12 AM, John McKerrell <john at mckerrell.net> wrote:

> My guess would be that the way is too long. Can you try chopping it up into
> sections, I'm not sure what the current best practice for way length is but
> you could start by trying somewhere between 5-10 miles.

I don't think that would be the problem. I routinely create ways that
are hundreds of miles long and they render properly. I have to split
my GPS traces into ways that are 20 - 30 miles long so I can unlock
them in Potlatch, but then after getting them converted into ways, I
reassemble the roadway back into a single way.

Here's a portion of the Alaska Highway from Fort St. John to just
south of Fort Nelson, that I laid down from a GPS trace (a portion of
the same GPS trace that the section of highway I'm having trouble with
was created from...)
http://www.openstreetmap.org/browse/way/27400400
As you can see, OSM has no problem rendering sections of highway that
are over 5 - 10 miles long.

> You mention forcing a re-render on
> informationfreeway, do you know that doing that will only affect the
> Osmarender/Tiles at Home layer. If you look at that layer you'll see that the
> tile containing your way is actually empty. I

I guess really that's another issue entirely. A couple weeks ago the
Osmarender map up and died. It used to render tiles properly, and then
one day everything went blue with "Unknown Type" in the middle of the
tiles. I think this issue with Mapnik showed up around the same time
as Osmarender went south, but is probably not related at all.

I guess taking a step back, the question is: Has there been some kind
of wholesale change in the rendering rules in Osmarender? It's
possible that there are tags that are no longer supported which cause
the Unknown Type issue there.

The Osmarender map likes to take areas defined as natural:water, and
turn them into squares of blue on occasion, I had assumed that this
was one of those hiccups, and it would rectify itself after a while.
http://www.openstreetmap.org/?lat=63.87&lon=-104.35&zoom=6&layers=0B00TTF

James




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