OpenGeofiction
Hello fellow mappers! I’ve got a bit of a pet peeve and was wondering if anyone on here could help.
Whether it’s a border (multi-polygons), an area, a river or whatever. I’d like to know if any of you can give me some tips and tricks for when it comes to overlapping lines which should belong to different relations, so I don’t have to redraw said complex object several times.
Practically, let’s say I want to make a national park follow the coastline - how would I do that without painstakingly making every single dot alongside the coastline a part of said relation?
Thank you in advance, Thanik.
Discussion
Comment from wangi on 16 September 2018 at 00:04
Well relations are built off of ways, so you split the ways and then associate with the relevant ways?
In your specific example you’d split the coastline, and then add that bit of coast to the relation.
Comment from LemonKing on 16 September 2018 at 08:58
To be precise, a border is not a multi-polygon, it is a type=boundary relation. In the example, the national park would not be defined as an area, nor as a type=multipolygon relation including several areas, but as a boundary relation. Ways included in the boundary relation (coastline ways, boundary ways, river ways, undefined ways etc) should add up to one or more closed areas, but not defined as areas.
Comment from Jake Knight on 16 September 2018 at 14:49
Here’s my method:
First, split the first polygon/line you have (in your case the coast) into a section which you want the drawn line to go over. Then, (assuming you are using JOSM) make a parallel line to this one, but with <0.0m displacement. This overlaps two lines, with the same tags for both. Move one node of one line, and select the original to rejoin it together. Then add nodes to the end of your new line and re-tag (national Park for you) to what you want it to be. Then, click to upload, but cancel as this highlights the node pairs which essentially lie on top of each other instead of joined as one. Go into validation, find the one which says something like naturally duplicated mixed nodes (in warnings I think) and click fix. This should work, and, once you practise, takes about 10 seconds compared to manually drawing out each node which takes a heck of a lot longer.
Hope this helps, Jake
Comment from wangi on 16 September 2018 at 15:13
Huh? If you really so want lines atop lines then pressing f will get you that, without all that rigmarole.
Comment from Thanik on 16 September 2018 at 16:28
A big thanks to everyone who responded, but I found out boundary objects can exist in multiple relations at once - thus easing this particular issue.
Currently, I have a similar problem but with areas, and this time it’s clear a single line can’t belong to two multipolygons, thus I’ll try some of the methods given here and report back with my progress.
Comment from Reece202 on 16 September 2018 at 23:54
But they can:
https://opengeofiction.net/way/10696508
https://opengeofiction.net/relation/95946
https://opengeofiction.net/relation/95945
The whole idea between relations and multipolygons is to allow lines to be reused. These are (as far as I know) no restrictions as to how many times a line (or node for that matter) can be referenced in relations.
Comment from Thanik on 17 September 2018 at 12:38
In relations, yeah, but I can’t use them in different areas as far as I know. I can’t link a ‘water’ area with a riverbank using a single line without converting one to the other or something along those lines.
Or JOSM is lying to me lol.
Comment from wangi on 17 September 2018 at 12:41
Can you sketch out, or screenshot what you’re trying to do… Because I think something is being missed here!