Why doesn't this significant building appear on Mapnik?

eteb3 · 2018-11-26T15:22:48.000Z

I hope these newbie questions don’t get wearing…

I’ve been scratching my head as to why the very significant Peterborough Guildhall doesn’t show up in Mapnik as a building, only as a disembodied name:
photo | permalink to OSM object | iD wireframe on Mapnik render so you can see what I’m looking at.

I wondered if it’s because it’s ‘covered over’ by the pedestrian area here?
https://www.openstreetmap.org/way/590865088

If so, would there be a way of showing the pedestrian area differently? (As a relation, with the Guildhall polygon forming an inner boundary?)

There’s a pic of Cathedral Square here if it’s useful - edge of Guildhall is just visible on the left of the pic, which faces east.

I know I’ll probably to be told ‘don’t tag for the renderer’ - so a solution that doesn’t tend that way that would be great!

Thanks all as always.

wowik · 2018-11-26T16:02:46.000Z

This is old mapnik bug/feature.

SomeoneElse · 2018-11-26T16:19:41.000Z

It’s actually a styling decision by the developers of that map style. You’ll need to “cut a hole” in the pedestrian area for it to appear. In a sense that’s correct - the pedestrian area doesn’t “extend underneath” the guildhall I guess.

Other maps may make different styling decisions - https://map.atownsend.org.uk/maps/map/map.html#zoom=19&lat=52.572696&lon=-0.243432 is one example.

kocio · 2018-11-26T16:22:52.000Z

Well, this is the old problem with how OSM Carto treats buildings and pedestrian areas. It was done by design and there’s no simple solution for that:

https://github.com/gravitystorm/openstreetmap-carto/issues/688

eteb3 · 2018-11-26T17:58:37.000Z

Thanks all.

SomeoneElse:

You’ll need to “cut a hole” in the pedestrian area for it to appear.

How would I go about that? Could I give the tag foot=no to the building? Or would dealing with Cathedral Sq as a relation work?

SomeoneElse · 2018-11-26T18:01:37.000Z

Yes, you’ll need to make it a “multipolygon” relation. See https://wiki.openstreetmap.org/wiki/Multipolygon_Examples#Forest_with_lake_.28One_outer_and_one_inner_ring.29 for more details.

eteb3 · 2018-11-27T13:56:51.000Z

Thanks, that’s very helpful - I did that, and then today there was one further edit from mboeringa.

From which I can infer, for anyone finding this thread:

Once you’ve merged the closed ways into a multipolygon, you will need to remove tags from the larger area (ie, the closed way that is now the outer boundary of the multipolygon).

Mecki · 2018-11-28T19:57:13.000Z

Yes, as written here: https://wiki.openstreetmap.org/wiki/Relation:multipolygon#Usage

kocio · 2018-11-30T04:59:18.000Z

After some thinking: making holes is perfectly sane way. Squares are not necessary the same as pedestrian areas, they can contain buildings, green patches, fountains etc. You should tag square with a place=square (with no holes, of course) to indicate that both pedestrian area and building belong to the same square.

eteb3 · 2018-12-07T10:00:52.000Z

Thanks both.

kocio - just seen this. So would the relation be

place=square + name=Cathedral Square

with members as

pedestrian area (outer)

building as hole in area (inner)
greens as hole in area (inner)
etc (inner)

?

alester · 2018-12-07T17:11:54.000Z

eteb3:

Thanks both.

kocio - just seen this. So would the relation be

place=square + name=Cathedral Square

with members as

pedestrian area (outer)

building as hole in area (inner)
greens as hole in area (inner)
etc (inner)

?

I would do it the opposite way. The relation should be the pedestrian area, because that’s the one that needs the holes cut out of it. Then, the outer way can be the place=square, which would cover everything inside that way (including the holes, because the way doesn’t have anything cut out of it).

kocio · 2018-12-07T17:54:32.000Z

I agree with @alester.

eteb3 · 2018-12-10T23:23:25.000Z

Thanks both.