[Talk-ca] CanVec Data Oddities

[G. Michael Carter]

The first problem is how JOSM select objects.  If a node is shared 
between a wood, marsh, body of water, and rapids.  Deleting the wooded 
area shouldn't remove the node from the other three as well.   When I 
remove the wooded area on one object the water disappears and the rapids 
turn into, what looks like two triangles touching each other. :-)

So that one there's no change needed to the CanVec Data, just that 
people deleting objects for an import need to be aware that it can 
change the surrounding objects of your not watching.   After that 
e-mail, I came up with the following to separate the CanVec data into a 
Navigation only layer.   That way I wouldn't have to "delete" anything 
in JOSM.  The only problem I haven't worked out yet is dealing with 
multi-polygons, as the inner/outer objects have no tags so there's 
nothing to filter on in the osmosis tool.  (and the sed commands are 
because the CanVec data is not formatted correctly as a V6.0 file.   
version and timestamp are required in V6.0 of an osm file, but it's 
easily added by sed)

     sed "s/<node /<node version=\'1\' 
timestamp=\'2009-08-11T15:16:48Z\' /g" $BaseName.osm | \
       sed "s/<relation /<relation version=\'1\' 
timestamp=\'2009-08-11T15:16:48Z\' /g" |\
       sed "s/<way /<way version=\'1\' 
timestamp=\'2009-08-11T15:16:48Z\' /g" |\
       osmosis --read-xml file="/dev/stdin" \
         --tf accept-ways addr:interpolation=* highway=* addr:city=* \
         --tf accept-relations highway=* \
         --used-node --write-xml $DirName/navigation-$BaseName.osm

The other issue was things like "sports tracks" that spanned two 
tiles.   Most objects have the two points on the border connecting so 
that the object is a closed object.  Sports tracks are like a two horse 
shoes.   They join no problem but only if both tiles are imported.   If 
only one tile is imported you'll have a very weird looking objected as 
it's expecting it to be closed.   Not really a problem with the CanVec 
data, just something to be aware of when importing.

Michael


On 19/07/10 08:23 AM, Bégin, Daniel wrote:
> Hi Michael,
>
> I'm not sure I understand the problem you describe.  Is it a problem with the geometric model?
>
> However, there is something I'm sure of - Nodes must be merged at Canvec tile limits to keep data integrity.
>
> Daniel
>
> -----Original Message-----
> From: talk-ca-bounces at openstreetmap.org [mailto:talk-ca-bounces at openstreetmap.org] On Behalf Of G. Michael Carter
> Sent: 18 juillet 2010 10:40
> To: Talk-CA OpenStreetMap
> Subject: [Talk-ca] CanVec Data Oddities
>
> I've been noticing some very rare occurrences where the track, park and campsite objects didn't make sense.  Found two causes:
>
> 1.  When deleting objects, like says woods, if it shares common nodes with another object like a campsite or rapids there's a 50/50 chance the
> delete will delete the shared nodes.   This is what I've found doing a
> recent object.   So something to look out for.
>
> 2. If the object is right on a CanVec border sometimes the way is not
> connected.   So you need to pull both tiles to get the complete object.
>
>
>
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>    


-- 
*G. Michael Carter*
Contact: H: 1-519-940-8935 | W: 1-905-267-8494 | M: 1-519-215-1869 | F: 
1-519-941-0009
Google Talk: xmpp:mikeycarter1974 at gmail.com

<http://www.openstreetmap.org/?lat=43.9216&lon=-80.105&zoom=14&layers=B000FTF> 
<http://livedvd.carterfamily.ca/>
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