[Talk-ca] Bodies of seawater in Canada - area definitions

[Iain Ingram]

I do have a question about the relations. If this is such and issue why are we allowing these edits in the first place? Should this be something that OSM changes? 

In my area (Calgary) I several several edits to rivers and lake relation being carried out by the facebook mapping teams. Should we be reaching out to these groups and instructing them to stop? 

My personal opinion is if David wants to maintain and do these large edits I am not clear on a problem. Database performance aside as I would see this falling into regular issues. If we see the database straining now we will see it in a year regardless.

Just my two cents. 

> On Oct 21, 2021, at 11:04, David E. Nelson via Talk-ca <talk-ca at openstreetmap.org> wrote:
> 
> 
> And like I said, I am willing to do ongoing maintenance of this dataset.  If someone still wants to alter the coastline, they can do so without worry.  I have the OSM Inspector to help me check if any of these seawater relations end up broken, so I can fix them.  And I try to keep my changesets small in terms of number of entities uploaded per set.  Besides, FWIW, Hudson Bay already has an area definition in OSM, relation #9441240, with over 8700 member ways in it.  Not everybody may have the patience to edit a relation like that, but I certainly do.
> 
> - David E. Nelson
> OSM user "DENelson83"
> Courtenay, BC, Canada
> 
> On Oct. 21, 2021 09:36, John Whelan <jwhelan0112 at gmail.com> wrote:
> Taking it a bit off topic.
> 
> Size makes a difference.  A relationship of two nodes that no one touches very much doesn't matter very much on the performance side.  A relationship with lots of nodes or ways or whatever is more likely to have something changed.  When a change occurs, and I'm guessing at this point based on experience we write the entire relationship to the history database.
> 
> Then we get into does the history database matter.  Well it's useful to look at the mapper sometimes, one who has mapped twice three years ago I might just correct something.  One with 20,000 edits and mapped yesterday I might try a changeset comment.  I think Fredrick commented that the history file for some relations is of such a size that it times out before being able to return the history.  It does depend on popularity.  One local foot bridge next to Ottawa University seems to attract lots of students who correct it by an inch or so almost like a rite of passage.
> 
> The other side of keeping databases slim and tidy might be to assume every highway in Africa apart from residential has a default value of unlit.  We don't make that assumption or anything similar but there are a number of highways in remote parts that are tagged lit=no. Having an unstated default value is not uncommon in databases, it keeps things mall but the value can be calculated.  I don't expect this will ever happen in OSM the decision making to too diverse.
> 
> The final comment would be not every mapper knows how to change something in a relationship.  The problem here becomes were someone wants to correct the local map but is unable to do so without spending time working out how to do it.  Locally we have one or two mappers with very specialist knowledge who don't map in OSM very much but their contributions are accurate.
> 
> Cheerio John
> 
> Jarek Piórkowski wrote on 10/20/2021 9:40 PM:
> On Wed, 20 Oct 2021 at 17:15, Frederik Ramm <frederik at remote.org> wrote:
> What's more, these waterbodies do not have an observable or even well
> defined outer boundary, forcing waterbody mappers to invent random
> straight lines on the far side of some gulf or bay or whatever. This
> runs counter to our maxim of mapping what is verifiable on the ground.
> This is true of most natural features. When will we be deleting the
> Alps (relation/2698607) or the Berliner Urstromtal (relation/2218270)?
> 
> If I wanted to push things to an absurd extreme, coasts are not
> observable on a micro scale, clearly anyone mapping coasts is doing so
> along a made-up boundary just to get a nice blue body of water roughly
> where they think it should be.
> 
> I would also be interested as to how political boundaries (of
> municipalities, states, etc) are verifiable on the ground their entire
> length. We can start keeping the database slim and tidy by deleting
> those.
> 
> --Jarek
> 
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