Residential render below trunk link

[Rovastar]

Currently residential renders above the trunk link like here.

http://www.openstreetmap.org/#map=19/52.92545/-1.50992

Probably need to look at all the layer ordering for link roads as they I think are pushed to the bottom.

[matthijsmelissen]

Thanks for reporting that. I will look at it.

[Rovastar]

Excellent. As you are looking at roads it makes sense to pick it up. Otherwise I'll get to it at some point.
I'll have a look for any more road anomalies too and post anything I find.

[matkoniecz]

the same class of problem: http://www.openstreetmap.org/?mlat=50.08111&mlon=19.88903#map=19/50.08111/19.88903 (fixed as of 2014-02-09) and http://www.openstreetmap.org/?mlat=50.07957&mlon=19.88927#map=18/50.07957/19.88927

[matthijsmelissen]

I think that there is unfortunately no clear solution, because in some cases (links ending in a T junction on residential roads or other lower types or roads), we do want the lower type of road to be drawn on top of the link.

[Rovastar]

Overall I think the situation can be improved with a more simple reordering. All link roads are currently render first and everything else is put on top we just need to move these up a little. I was say, thinking Motorway link above Secondary or maybe Primary roads. Trunk link above tertiary or maybe secondary roads, etc need to think in a bit more detail what the very best ordering is.
Occasionally you want to see other info but the majority of cases should look much better.

[matthijsmelissen]

That's a heuristic solution that would still break many situations, like here: http://www.openstreetmap.org/#map=17/51.63670/-2.45155

[matthijsmelissen]

@Rovastar I'm not really sure how to approach this issue. You suggest not worrying about edge cases, but to me, http://www.openstreetmap.org/#map=17/41.05566/14.57152 seems to be an edge case - perhaps even a mistagging, shouldn't the road to the right be primary instead of primary_link? I would be happy with any suggestions / proposals / ideas.

[Rovastar]

I suppose I was thinking of cases we can improve first. E.g. Motorway, (trunk, secondary) links are to be rendered above footpath, service roads, living streets, tracks, etc.
let's go all the way up to unclassified as you have seen tertiary cases.
about the edge cases my point is that sometimes things will look different and we should not be worried if overall it is improved.

[matthijsmelissen]

Yes, that would make sense.

What would be the best way to accomplish this? Creating a separate layer for every road type is not the best solution, I think, so the SQL output should be ordered correctly already. We currently render by z_order. We could add a manual ORDER BY in the SQL, something like

ORDER BY case when highway = 'motorway' then 3 when highway = 'motorway_link' then 2 when highway = 'footway' then 1 [...] end

but that looks ugly, and might come with a huge performance penalty.

I think the best option would be to change osm2pgsql, and populate the z_order field in such a way that footpaths, service roads, living streets, tracks etc. have a lower z_order then link roads.

Could we accomplish this by merely changing the osm2pgsql stylesheet, or would we need to patch osm2pgsql itself?

[matthijsmelissen]

Google Maps suffers from the same issue, see for example here:
https://www.google.co.uk/maps?q=Coventry&hl=en&ll=52.404358,-1.506441&spn=0.001257,0.002411&sll=50.080333,19.889835&sspn=0.005288,0.009645&oq=coventr&hnear=Coventry,+West+Midlands,+United+Kingdom&t=m&z=19

[matkoniecz]

see also https://trac.openstreetmap.org/ticket/2024

[matthijsmelissen]

Resolved by #626.

[matthijsmelissen]

@mkoniecz's problem is solved but the original one is still open. Reopened for further investigation.

[matthijsmelissen]

The original issue was not accurately tagged/traced, I improved the tagging. It's not clear if a further fix is necessary or possible. I will therefore close this issue for now. If there are other situations like this, feel free to create a new issue (or reply to this one).

[pnorman]

closing as per #266 (comment)

[Rovastar]

I didn't realise that junction had changed. It wasn't tagged incorrectly at the time (it did really cross the two links) but the junction has now it seems changed.

I am not sure this issue is actually closed. Unclassified should go under trunk links. But the whole links thing needs looking at anyway.