[talk-au] PSMA Administrative Boundaries

[Lee Mason]

Nice work on cleaning up the PSMA data, Andrew. It looks a lot easier to manage for importing now.



A quick look at the data, and it appears there is some regional/state variance in the boundaries:

Some of the WA LGAs extend out to the coastal waters limit.

VIC LGAs mostly approximate the high tide mark (except around Port Welshpool) and are shared with the locality boundaries.

TAS LGAs mostly extend to the low tide mark and are not shared with locality boundaries.



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In regards to discussion earlier about aligning boundaries to existing features; I think that if a mapper determines that a boundary and a feature approximate each other, they can be merged. But it should not be a requirement to align or not align features.



For example, when an admin boundary clearly defines the left side of a river, it should be separate. But as the river becomes a stream and is narrower and more ambiguous, it would provide a tidier map to align the two features at this point.



Whilst this does mean a decrease in the accuracy of the data on OSM, if a data user requires the precision to determine if an admin boundary is on the left or right side of a road or river, they should (or would) be using the authoritative data source anyway because OSM can never guarantee that level of accuracy. It also means it is less of an issue when future users inadvertently try to “fix” the map by aligning admin boundaries with rivers, etc.



So I would suggest that mappers use their own good judgement to align a boundary and a feature that very closely approximate each other if they wish to do so.



With the same reasoning, I think if an admin boundary closely approximates the hightide mark, it should be aligned with the OSM coastline.



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Speaking from the perspective of Tasmania’s data, my suggestion is:

Tassie LGAs would not be aligned with the coastline because they follow the low tide mark.

Localities would be aligned to the OSM coastline because they approximate the high tide mark.



And I would probably import Tasmania by doing 1 LGA at a time (including the contained localities).



Cheers

Lee





________________________________
From: Andrew Harvey <andrew.harvey4 at gmail.com>
Sent: Sunday, October 7, 2018 6:32:02 PM
To: OSM Australian Talk List
Subject: Re: [talk-au] PSMA Administrative Boundaries

I've approached this from the angle of what we'd need to get the data
to look like if importing as is into OSM. I couldn't find any tools
which correctly ensure that boundary ways were shared via relations
instead of duplicated so I wrote some new tools. The process I used is
documented at https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fandrewharvey%2Fpsma-admin-bdy2osm&data=02%7C01%7C%7C6fa5cf91925e4f1f3a4d08d62c2734a6%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636744944223052969&sdata=wwiO1AL7k1rZAvsf5Igz6SsC758fwZ%2BxdYKdnmj4Upo%3D&reserved=0

The processed AUGUST 2018 LGA + Suburb/Locality OSM file is at

https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftianjara.net%2Fdata%2FPSMA_Admin_Bdy.osm.pbf&data=02%7C01%7C%7C6fa5cf91925e4f1f3a4d08d62c2734a6%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636744944223052969&sdata=EH3xdg4az3Ps1T8iQIjqJ6H9ui3lZZ36cjTns4xHTvk%3D&reserved=0

The file is quite big so you'll need enough memory to open it in JOSM.

In JOSM you can open this directly with the PBF plugin otherwise any
of the software at
https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwiki.openstreetmap.org%2Fwiki%2FPBF%2FSoftware_Compliance&data=02%7C01%7C%7C6fa5cf91925e4f1f3a4d08d62c2734a6%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636744944223052969&sdata=D06VwqI21v7Oqk36bFLgJUcrBWCzY7NpzDPk3zIn%2BuE%3D&reserved=0 can
deflate it.

I see the next steps are to:

- discuss if this is the right format for upload or not,
- how we'll manage that upload in terms of breaking it up into smaller pieces
- if there is any re-using of existing ways or not
- how to ensure we're retaining the existing LGA/Suburb data in OSM.
This includes both relations and those mapped as points (as Joel
touched on). Those mapped as points are likely suitable for either the
label or admin_center members of the relation.

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