OpenStreetMap

Canadian coast

Posted by DENelson83 on 19 October 2021 in English.

In case you are wondering what I am scheming with my recent changesets, I have started converting individually-named bodies of water on the Atlantic coast of Canada to relations. I started with Cobequid Bay, progressed out the Bay of Fundy to Passamaquoddy Bay and St. Marys Bay, and I have subsequently rounded Cape Sable Island and gotten as far northeast as Liverpool Harbour, progressing towards Halifax. What I am intending to do with this series of edits is to make relations for bodies of water throughout the entire coast of Canada, from the Bay of Fundy all the way to the Beaufort Sea. I have already done this for the Pacific coast, and I figured I might continue this through the rest of the coastal areas of the country. And this little pet project is going to take quite a bit of time to complete, given just how vast Canada is and how much coastline she has, the most out of any country in the world.

Discussion

Comment from SimonPoole on 20 October 2021 at 08:25

I suspect you might want to pause this and get community input before you invest too much time.

I believe the general consensus right now is to -not- map body of waters with relations as practically unmaintainable.

Comment from DENelson83 on 20 October 2021 at 08:43

I fail to see how these relations would be unmaintainable, given there are tools to help with such maintenance, such as OSM Inspector. Plus, the JOSM validator recommends to define bodies of water as areas instead of just points, and I have been taking steps to preserve the integrity of the existing OSM data.

Besides, personally, this is another way for me to express my patriotism for the country I was born in and have lived in all my life.

Comment from woodpeck on 20 October 2021 at 09:50

In my opinion this is not a good idea since (a) any future edit to any part of the coastline will create a new version of those giant polygons you are creating, thereby making such coastline edits more cumbersome, slower to upload, more likely to have a version conflict and so on, i.e. you are making it harder for others to contribute; and (b) you’re very likely introducing random guesswork lines at the outer boundaries of the bays etc. you are mapping i.e. you are deliberately introducing wrong data just to see a label on the map.

In my opinion, your polygons are likely to get deleted at some point in the future, and until then they will have cost you a lot of work and others a lot of nerves, all for nothing.

Comment from DENelson83 on 20 October 2021 at 10:11

“any future edit to any part of the coastline will create a new version of those giant polygons you are creating”

But isn’t that what is already happening with all the other big polygons imported from CanVec, like woodland data?

Comment from Russ on 31 October 2021 at 12:23

I think there are unanswered logistical questions around naming large areas of sea (oceans being the extreme example - it would be deeply impractical to map those as relations).

I agree that these should ideally be mapped as areas/relations so that their rendering importance can be estimated easily.

I don’t really agree with surveyability concerns here - the same surveyability issue extends to place names and other geographical features. They are to some extent subjective and impossible to define precisely, but this is unavoidable and it doesn’t mean we shouldn’t try to map them. In coastal areas, the names of sea features can be as important as land features and I strongly feel that we shouldn’t ignore them.

I know seems messy, but the way we tend to approach this in the UK is by mapping these large features as a completely separate, simplified area unattached to the coastline (example).

This means that changes to the coastline aren’t going to affect these objects and they’re much less likely to cause unexpected performance issues. People who aren’t concerned with them can completely ignore them. It makes very little difference to renderers (in fact simpler polygons are likely faster to operate on).

I’d recommend considering this approach for larger marine features in excess of a few tens of square kilometers.

Comment from Mateusz Konieczny on 31 October 2021 at 13:15

But isn’t that what is already happening with all the other big polygons imported from CanVec, like woodland data?

Forest multipolygon with thousands of elements are also mistake that should be fixed.

Comment from Jarek Piórkowski on 1 November 2021 at 01:11

Hello all, I was reminded of this diary entry by weeklyOSM https://weeklyosm.eu/archives/14940 after the discussion on talk-ca https://lists.openstreetmap.org/pipermail/talk-ca/2021-October/010127.html

I find the objections raised by commenters here and in the talk-ca thread interesting.

Warning, example relation links posted here are for huge relations that might seriously slow your browser.

The maintainability and “cumbersomeness” hasn’t stopped OSM from adding any other amount of detail. I could point to examples like PTv2 relations for long-distance buses such as https://www.openstreetmap.org/relation/10715333 spanning hundreds of kilometres and thousands of OSM ways. This is a tooling and database issue and as far as I know OSM’s approach has always been to make the database as good as possible and not worry about storage or RAM.

Lack of community consensus hasn’t stopped relations for the Alps https://www.openstreetmap.org/relation/2698607 (did you know Vienna is in the Alps?), for the Berliner Urstromtal https://www.openstreetmap.org/relation/2218270 (with fuzzy borders drawn as random guesswork long straight lines), or indeed if we wish for maritime examples, for the Pomeranian Bay (https://www.openstreetmap.org/relation/9037646) which even has that imaginary straight line “separating” it from the main sea.

I gave two of these examples in a response to woodpeck/Frederik Ramm on talk-ca, unfortunately to no response.

Now, you can say that there is no consensus that adding these examples in Europe was a good idea. But evidently there is also no consensus that adding these is a bad idea and that they should be deleted. Until these prominent examples in Europe are addressed in some way, trying to claim “no consensus” for the same kind of edits in Canada feels more than a little like pulling up the drawbridge once you’re in.

Comment from DENelson83 on 1 November 2021 at 04:08

Well, as you can see, Jarek, I have abruptly stopped this project in its tracks just short of Halifax because of the blowback I have received in response. I did add a tag to all of these relations to allow editors to easily filter them out if they want no part of them while they are editing coastlines, in response to the ensuing discussion I took part in on the talk-ca list, and I am perfectly fine with people breaking these relations if they want to do coastline edits, as long as I make regular trips to OSM Inspector to see which such relations have been broken, so I can repair them. As I have said earlier, I am willing to maintain this data myself. However, this project gave me something with which to occupy my time, and I would really be grateful to at least be allowed to continue with it.

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