[Talk-ca] Administrative boundaries Quebec
steggink at steggink.org
Tue Jan 19 02:43:12 GMT 2010
As a bit of a challenge I've looked at the administrative data pointed
out by Nicolas Gignac: . I know there are some doubts about the
accuracy, but this was also meant as an exercise to deal with this kind
of data. Maybe it can be reused for other purposes, although I haven't
written the tool I used in a generic way. I also hope that the more
accurate (1:20k) data uses the same structure.
First I converted this data to SHP (with an ESRI tool called Import71,
and then ogr2ogr). Then it was converted to OSM with shp-to-osm.jar.
However, the data has a topological structure, so it has not much value
if it would be imported into OSM directly.
The set of administrative boundaries contains municipalities, MRCs,
administrative regions (17) and urban agglomerates. The municipal data
contains also information about MRC, admin. regions and agglomerates, so
I decided to examine this further. Now the topological structure was a
benefit, because this is how administrative boundaries should also be
entered in OSM. The boundaries only contain attributes like from-node,
to-node, left-poly and right-poly. However, this is enough to compose
relationships (type=multipolygon/boundary, boundary=administrative,
etc.) out of them. Because I ended with an ArcInfo coverage as a result
of the conversion by Import71, I decided to extract data from the file
pat.adf to get the municipality and other relevant names, codes, etc.
So far I have only created relationships, including the municipality
name. I would like to share it with you, in order to gather feedback.
The result can be found here: . PLEASE do NOT upload this data to
OSM! The ways are sorted in the relationship, so they form closed
chains. Also the nodes where multiple ways meet have been deduplicated,
otherwise JOSM (and also OSM itself) won't recognize the ways as being
connected. The deduplication was based on the actual coordinates, not
the node IDs used in the topology.
Things to do:
* Detect which boundary is the outer boundary, and which ones are the
inner boundaries. Obviously, the ring with the biggest surface area is
the outer boundary, and the rest are inner boundaries.
* Add multiple municipalities in the same relationship.
* Create MRCs, administrative regions, and urban agglomerates.
More information about administrative boundaries can be found in .
For Canadian provinces admin_level=4 should be used, for regional
municipalities (MRCs in Quebec) admin_level=6, and actual municipalities
admin_level=8. I would like to propose to use admin_level=5 for the
regions. They have at least a semi-offical status. Others might be able
to elaborate on it more. This leaves the urban agglomerates (Montreal
and Quebec only), for which admin_level=7 would be a natural choice,
although I'm not sure if they have any official status. What do you guys
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