On 23/09/2020 23:01, Paul Johnson wrote:
On Wed, Sep 23, 2020 at 4:37 PM stevea <stevea...@softworkers.com
<mailto:stevea...@softworkers.com>> wrote:
Paul Johnson <ba...@ursamundi.org <mailto:ba...@ursamundi.org>>
wrote:
> 2. Tagging route information on ways. It's about a decade too
long at this point for ref=* on a way to be completely
disconnected from the entity the tag applies to: That's why route
relations exist. Biggest problem child on this at the moment:
OSM's own tilesets. Let's drop rendering for ref=* on ways and
just render the route relations already, this and multipolygons
are why relations came to exist in the first place.
Yes, 100% agreement. I think this is simply pure inertia (the
kind that says "broken process") on the part of renderers.
Can anybody (renderer authors included, maybe even especially) are
welcome to offer reasons why "the old machinery" remains in
place? Are there legacy use cases that remain unclear to the
wider community? Please tell us here, if so.
The US is unusual in that it doesn't have a single ref per section of
road. Most places in OSM map what they see on the ground, and the
current OSM Carto rendering works just fine for them.
While I still find murky and mysterious exactly "how" to effect
change in renderers (who you gonna call?),
When it was clear that the direction of travel for OSM Carto wasn't
going to be useful t me I forked what was there at the time and started
going in a slightly different direction.
my two best efforts along these lines are to "tag well" and "wiki
well." (And that can include a great deal of discussion and
consensus building on its own, no doubt). Eventually, (and I've
discovered it can take years), renderers do catch up.
To be clear, I don't want to throw any humans under the bus on this,
since the Carto folks really do make an elegant style for Mapnik.
Though if this is a Mapnik issue that's preventing this, maybe it's
time to either fix Mapnik or consider alternatives?
It's not strictly a Mapnik problem. It's certainly possible to render
information from relations in Mapnik (I've done it, for different sorts
of relations, and written diary entries about it). There are a couple
of tricky bits* though:
1. You'd need to derive the shields from the ref and the road itself
from the way, and you're going to get some edge cases where they
"don't seem to match".
2. I expect that it would be _really_ difficult to render refs from
relations in the one country where that's needed and refs from ways
in the other 190-odd. The OSM style is a global style, and that
means that local edge cases (which is what the US is here) can't get
the "special-case handling" that might be nice.
3. The infrequency with which OSM data is loaded now means that more
has to be done "on the fly" rather than "at data load", which
somewhat limits the options for how to solve the problem.
I'm actually surprised that someone associated with the OSM US community
hasn't created a proof-of-concept "good US road route rendering" variant
of the OSM Carto style on a live server that people can use for
reference (I'm guessing ongoing server costs wouldn't be huge - a couple
of $ a day at one of the cheaper hosters). Of the issues above (1) you
can ignore in a proof of concept (or deal with some of the edge cases),
(2) isn't an issue if you're just rendering the US and (3) isn't a
problem if you can live with downtime at the occasional reload (or have
two databases - one live, one available to be reloaded if you can't).
Best Regards,
Andy
* I've deliberately simplified things here for legibility - there's lots
of discussion about these issues in OSM Carto's github, and there are
also osm2pgsql options available now (see
https://pavie.info/2020/03/09/openstreetmap-data-processing-osm2pgsql-flex/
) that weren't an option previously that may really help here.
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