OpenGeofiction
Ran the JOSM validator over this section of map:
http://opengeofiction.net//#map=17/-8.4501/171.8488
And got 13 errors related multipolygons, affecting these items:
relation 74797 relation 74796 relation 74799 relation 74798 relation 74801 relation 74800 relation 74672 way 8175720 way 8175721 way 8175722 way 8175717 way 8175718 way 8175719
And I have no clue how to begin fixing them. If someone could clean this up into something resembling sensible data, it would be appreciated.
Discussion
Comment from ADB52 on 22 August 2017 at 09:19
I suggest to read up on the use of multipolygons. You have made a number of multipolygons in your river delta and made them ‘inner’, without referring to the ‘outer’ multipolygon that they are supposed to be ‘inner’ to. If you take your wetland areas and make them part of the river multipolygon, as inner, you’ll find that your errors will disappear.
Comment from skquinn on 22 August 2017 at 09:36
I’m not the one that made them like this (I use JOSM; the mapper that made this, not surprisingly, used iD). Obviously the multipolygons are botched, but I’m lost when it comes to figuring out what the original mapper might have meant, or at least something that actually makes sense.
Comment from Luciano on 22 August 2017 at 10:29
If the data is a mess, in a blue country, here is what I do:
1. First, who made it?
2. Use the “history” (in JOSM) to find out who made it. (Side note: I wish people used this functionality a lot more, especially in blue countries - it would improve dialogue and collaboration among mappers a lot).
3. Are they still active?
4. If they are active, send them a private message: “Your data is a mess. Wanna fix it?”
5. If that person says “no,” then proceed to #7.
6. If that person says “yes,” it’s their mess, not yours. Recommend to them that they fix it. Finished.
7. Next, is the work worth preserving?
8. If yes, then either repair, or in a situation where the mess is not easily resolvable, “re-engineer it” from scratch. Finished.
9. If no, just delete. Problem solved. Finished.
Alternative answer: if you’re interested in this from a technical standpoint (i.e. “Wow, this is messed up in an interesting way… I wonder why? Oh… iD! That explains it.”) then go ahead and study it, I guess. I’ve learned a lot of what I know from situations like this. From a technical standpoint, I think this is actually pretty easy to fix - throw away most of the multipolygons, and enroll all the ways with correct roles in one of them. I’d also get rid of the overlapping water shoreline/coast way (i.e. split the coast and enroll that piece, too, in the water relation).
tl;dr answer: don’t worry about it. Someone can fix it, eventually.