CanVec question

I’m working on creating a MapRoulette challenge covering the whole planet.

The challenge asks people to review situations where someone has drawn an island (place=island or islet) on the map but forgotten to add it as an inner to the surrounding water body. As a result, the island doesn’t render on our maps (not on any of the maps on, anyway).

A typical example is here.

Sometimes the island does render, because it has also some other tag that renders over water, such as natural=wood. In those cases, I am still planning to ask mappers to add it to the multipolygon relation, because semantically it doesn’t make sense to say the island is part of the water just because it has wood on it. (Let me know if you disagree.)

Sometimes there are duplicate ways, sharing the same nodes, one tagged place=island and one tagged natural=wood. In those cases I am planning to ask the mappers to merge the two ways. (This is automatically flagged by JOSM’s validator.)

A situation that’s quite common in Canada (more than 3,000 islands if I am counting right) is where the CanVec import has created duplicate ways for wooded islands, one natural=wood and one place=island, that share the same nodes but they have conflicting canvec:CODE and canvec:UUID tags. Sometimes there’s even a third copy of the way, which only serves as the inner to the water body. In these cases the overlapping ways can’t simply be merged, the mapper would have to discard one (or both) of the CanVec tags. Example island and wood.

I’m wondering if I should include these in the MapRoulette challenge, and, if so, what to ask mappers to do.

(1) Would you like to see the overlapping wood and island merged? Or would you rather keep both?
(2) If you would like to see them merged, which of the CanVec tags should be kept?


For the CanVec stuff, my personal preference would be to merge the ways in a bulk edit presuming you have a robust way to identify them. One person dealing with it in an automated way is much less likely to leave behind a trail of broke relations than just having a computer do it. Arguably, it’s just finishing cleanup of the original CanVec import.


Thanks. I’ll exclude the islands with a CanVec tag from the challenge then.

I think in principle it would be great to consolidate these, but there are other overarching problems with the Canvec data that was imported 15 years ago.

E.g., at your example islet in the middle of Kennibik Lake, there’s not only overlapping place=island and natural=wood objects, but there’s also a simple line that serves as an inner boundary for the Kennibik Lake multipolygon relation. These should all be merged into one.

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Yes, in some cases I found four overlapping lines!

You would still need to decide what to do with the conflicting IDs.