[OSM-talk] multipolygon source tags preferred method

Martin Raifer tyr.asd at gmail.com
Tue Mar 28 07:44:46 UTC 2017


> I didn't know that iD doesn't allow you to set the source on the changesets as somebody mentioned. If that is true, I see this as a shortcoming of iD that should be fixed.

iD has changeset tag editing since a few weeks (which allows anyone to
set the changeset's source tag). It just waits to be rolled out on
osm.org with the next minor release of iD. See
https://github.com/openstreetmap/iD/pull/3898

On Tue, Mar 28, 2017 at 9:25 AM, Jochen Topf <jochen at remote.org> wrote:
> On Mon, Mar 27, 2017 at 10:41:38AM +0200, Jochen Topf wrote:
>> On Mon, Mar 27, 2017 at 03:56:43PM +1000, nwastra wrote:
>> > I am unsure what is the preferred way or best practice to tag the source for multipolygons.
>> > I currently put the source on the relation with all the rest of the tags, and only adding tags to individual ways or inner polygons if they are also part of a seperate entity like a fence or a body of water. I also include the source with the uploaded change-set. This would seem to be ok when adding a new mp relation.
>> >
>> > Should the source also be added to all the individual ways that make up the outer and inner boundaries of each polygon?
>> > Is this also the preferred way when adding a new large mp relation that does not currently exist?
>> >
>> > When replacing individual ways or splitting and altering part of a way with updated data, adding the new source tag to those new ways would seem best practice or is it sufficient to added the source to the change-sets alone?
>> >
>> > Is the most sensible way to initially add the source tags to the relation and change-set upload alone and from then on as individual parts are amended, to add the source to just the updated/corrected ways and the change-set on upload?
>> >
>> > I have not come across guidance for this on the wki yet.
>>
>> Putting the sources on the objects has been deprecated for a while. The
>> source should be put on the changeset only. If you are doing edits that
>> involve several different sources, it is best to split the changes up
>> into different changesets. Of course this is not always possible, then
>> you can also put several sources in the changeset source tag.
>>
>> Adding the source to the objects was deprecated, too fined-grained
>> source tagging simply doesn't make much sense. We can not track every
>> source for every node, way, or relation or the parts of them for every
>> tiny change that somebody does. In the end most data will have multiple
>> sources and figuring out what came from what can only be done going
>> through the changeset tags, not by looking at the tags on the data
>> itself.
>
> I probably shouldn't have used the word "deprecated", because there is
> no mechanism in OSM do deprecate anything. This is more "common
> practice" really. Martin has already described why source tags on
> objects don't work well. In theory they might or might not be a good
> idea, but in practice we have seen in OSM that they don't work. The
> source tag is just not updated in a way that makes it useful. Since we
> introduced changesets, we can do better: We put the actual data into OSM
> objects, but the meta-data that describes the why and how of the mapping
> we put into the changesets. (I didn't know that iD doesn't allow you to
> set the source on the changesets as somebody mentioned. If that is true,
> I see this as a shortcoming of iD that should be fixed.) This has the
> added benefit of putting the meta-data that is seldomly used on the
> changesets keeping the actual OSM objects lean and mean.
>
> Now regarding the splitting up of changesets for different sources. If
> you are doing different things this absolutely makes sense and, I would
> argue, is even necessary to be able to add good changeset comments,
> which you should always do. So if you come back from a mapping survey
> and add the data you collected outside with source "survey" and then go
> to a different part of the planet and add a few things from "bing",
> those should be two changesets. Of course, if you add the geometry of a
> road from Bing and the name from your survey, it makes total sense to
> add the source "bing;survey" or something like it.
>
> As always, there are few hard-and-fast rules in OSM. That's good because
> everbody can decide for themselves which arguments they find convincing
> and which advice to follow. So if you want to keep adding "source" tags,
> that's fine, too.
>
> Jochen
> --
> Jochen Topf  jochen at remote.org  https://www.jochentopf.com/  +49-351-31778688
>
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