[Talk-ca] Administrative boundaries Quebec

Frank Steggink steggink at steggink.org
Sat Jan 23 04:46:49 GMT 2010


Frank Steggink wrote:
> Frank Steggink wrote:
>   
>> Hi,
>>
>> As a bit of a challenge I've looked at the administrative data pointed 
>> out by Nicolas Gignac: [1]. 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: [2]. 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 [3]. 
>> 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 
>> think?
>>
>> Regards,
>>
>> Frank
>>
>> [1] 
>> http://www.mrnf.gouv.qc.ca/territoire/portrait/portrait-donnees-mille.jsp
>> [2] http://www.steggink.org/osm/Quebec/quebec_munic.zip
>> [3] http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative
>>
>>
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>>
>>   
>>     
> A clarification on this: "Add multiple municipalities in the same 
> relationship." Several municipalities have exclaves, like outlying 
> islands. They are divided over multiple polygons, so I created multiple 
> relations for them.
>
> For the higher-level administrative boundaries, I intend to use 
> information from the AAT file which was generated by Import71. This file 
> contains records describing the boundary type. Although there is 
> specific data for each level, in OSM it would be best to reuse the same 
> set of nodes and ways, and that can best be done by using the same 
> source data.
>
> Frank
>
>
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>   

Hi all,

The last days I've flexed my Mapnik / osm2pgsql skills, and was able to 
put a visualization of the tiles online. They can be found here: [1]. 
The tiles themselves are generated as transparent PNGs, so they didn't 
have to be integrated into the data. Note that I also adjusted the 
zoomlevels, so they are visible earlier than they would be normally. 
Levels 6 - 13 are available, but the last level is still rendering as I 
write this. I haven't take care of any labeling yet, although it is 
present in the DB.

Cheers,

Frank

[1] http://mijndev.openstreetmap.nl/~fsteggink/quebec_admin.html





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