OpenStreetMap community

4185 readers

43 users here now

Everything #OpenStreetMap related is welcome: software releases, showing of your work, questions about how to tag something, as long as it has to do with OpenStreetMap or OpenStreetMap-related software.

OpenStreetMap is a map of the world, created by people like you and free to use under an open license.

Join OpenStreetMap and start mapping: https://www.openstreetmap.org.

There are many communication channels about OSM, many organized around a certain country or region. Discover them on https://openstreetmap.community

https://mapcomplete.org is an easy-to-use website to view, edit and add points (such as shops, restaurants and others)

https://learnosm.org/en/ has a lot of information for beginners too.

founded 4 years ago

MODERATORS

Ben_on_Lemmy@lemmy.ml

Using multipolygons on complex buildings? (lemdro.id)

submitted 10 months ago* (last edited 10 months ago) by governorkeagan@lemdro.id to c/openstreetmap@lemmy.ml

5 comments fedilink hide all child comments

I was updating my old high school on OSM and noticed that whoever mapped it before used a multipolygon to map the buildings. From what I can tell the benefit to this is that you can map more complex shapes by having them be related, is that correct?^2^

There are some buildings that have been added as building=yes instead of building=school (some haven't been marked at all) and I want to make sure I understand it better before I go and make any big changes.

^1^ my old high school for context - Esri World Imagery has the best image quality once you zoom in.
^2^ My understanding comes from this wiki page

EDIT:
Some extra clarification as to why I'm asking. There are some buildings that have been added as separate multipolygons which don't make sense to me. (see screenshot), these two buildings were added as separate multipolygons but they are connected and form part of the same building.

I also get a warning in JOSM that says "amenity inside amenity - amenity=school inside amenity=school"

you are viewing a single comment's thread
view the rest of the comments

[–] infeeeee@mastodon.social 16 points 10 months ago (1 children)

@governorkeagan you have to use a multipolygon if the building has "holes", e.g. interior gardens or similar things, there is simply no other way. I can see this is the case with your school.

About building=yes, that's the default. Usually you can't decide the type and usage of a building from aerial imagery, so you should just use 'yes' in that case. If you know the building you should fix its type.

[–] governorkeagan@lemdro.id 6 points 10 months ago (1 children)

Thanks for confirming that for me!

[–] infeeeee@mastodon.social 2 points 10 months ago (1 children)

@governorkeagan about your edit: that building should be part of the big building not separate. If you want to differentiate parts of the building you can use building:parts or indoor mapping. https://wiki.openstreetmap.org/wiki/Key:building:part https://wiki.openstreetmap.org/wiki/Simple_Indoor_Tagging

About the error: you should tag the school as an area OR as a node, not both. There is a detailed sectiom about this in the wiki, check the image in the section "How to map" https://wiki.openstreetmap.org/wiki/Tag:amenity%3Dschool

[–] governorkeagan@lemdro.id 1 points 10 months ago

That’s what I thought, I’ve made some changes in JOSM that fixes the error (tagged the school as an area). Thanks again for the help!