[Imports] Australian administrative boundaries import

[Andrew Harvey]

Thanks for reviewing this Rafael.

On Mon, 22 Oct 2018 at 22:52, Rafael Avila Coya <ravilacoya at gmail.com> wrote:
> I've been looking only a bit inside the data (file 1.osm) and I have
> some issues/questions:
>
> Running the JOSM validator, it throws the following errors and warnings:
>
> Errors:
>
> 2,384 duplicated way nodes.
> 864 intersection between multipolygon ways.
> 40 multipoligon members repeated with same role (they seem to be
> duplicated nodes as well)
> And 1 way contains twice a segment.
>
> Warnings:
>
> 43,708 crossing boundaries
> 3 overlapping ways
> 15 self-crossing ways
> 1,156 self-intersecting polygon rings, and
> 51 self-intersecting ways
>
> All these errors and warnings should be fixed before importing, and you
> should document how you will proceed to fix them in the import wiki.

Some of these are fixed in the simplified files.

However:

Error: Multipolygon member(s) repeated with same role
Error: Intersection between multipolygon ways - same as above
Warning: Crossing boundaries

All of these are most likely due to the original geometries being out
by around 0.1m so they aren't being snapped by the processing scripts,
I'll need to see if we can increase the tolerance to ensure these get
automatically snapped together to avoid these geometry issues.

The other warnings:

Long Segments - I'm not sure why we can't have long ways, I'm okay to
ignore this.

Relations with same members - This is expected, we can have an
admin_level 10 and admin_level 6 which are the same hence two
relations with the same members.

> I've seen that border ways aren't tagged. At least they should have the
> following tags [1]:
>
> boundary=administrative
> admin_level="the highest (lowest number) level it shares"

Right, I missed that since a lot of the existing ones in my area only
have the tags on the relation not on the ways, and JOSM and osm-carto
display them as admin boundaries even without the tag on the ways.

We can add the boundary=administrative tag, but adding the admin_level
of the highest level it shares, I'm not sure how we can easily do
that. It makes it harder for us human editors to maintain the data and
it's more error prone as could become out of sync with the relations.

> Adding source=* to those ways is also recommended.

Ok.

> Between the admin_level=6 Willoughby City and Ryde City councils, along
> the Lane Cove river, I see that the river basin is an admin_level_6
> "council" called "Unincorporated". Is that correct? I ask this because I
> see that the current OSM "Council of the city of Ryde" border
> (admin_level=6 too) goes along the centre of the river.

Truth is I don't know. The existing NSW LGA boundaries are from a NSW
source which has each LGA meet in the river centerline, this country
wide PSMA source says the river isn't part of any LGA and put's the
two LGAs to the riverbank on each side.

NSW already has these admin boundaries as you can see, so we're not
planning on importing NSW, however these are still good questions.

> I also see that the to-be-imported borders of Willoughby and Ryde city
> councils don't adapt to the river banks as they are now in OSM. Will
> things like these be manually conflated with existing OSM data? I don't
> see that in the wiki yet. Maybe that could be extended from the point
> "Apply any coastline conflation if using the existing coastline as some
> of the boundaries (or this can be done post-import)" that you have
> already in the Workflow section of the wiki, so river banks would be
> included in that conflation together with coastline.

Again good question. This has been discussed on the local au mailing
list. Most voices there preferred not to re-use existing
waterway/road/etc as part of the admin boundary relation. The two main
reasons given were:

1. if the watercourse moves then the admin boundary doesn't so they
shouldn't be linked
2. people end up breaking admin boundaries when they change roads, rivers etc.

There was a discussion a few years back about Unincorporated LGA areas
I think this is something we still need to work out
https://en.wikipedia.org/wiki/Unincorporated_area#Australia However,
these water based areas marked unincorporated, shouldn't be imported.
I agree we should add that to the wiki.

> As for the changeset tags, I would add:
>
> type=import
>
> Although not important, you may consider to change the source to:
>
> source=PSMA_Admin_Boundaries
>
> and add:
>
> source:date=August_2018

I've updated the changeset tags on the wiki, though I used the date
format 2018-08.

> The changeset tag review_requested=yes (available as an option already
> in JOSM (and iD)) may help you if you want to include validation in the
> workflow.

Ideally this review here would be the review, it's going to be better
to pick up things before rather than after.

>
> This is all that I've seen. I hope it can help you.

Yes it's always helpful to have an extra pair of eyes.