[Talk-ca] Users in Ottawa and Geobase

James A. Treacy treacy at debian.org
Thu Oct 29 18:11:47 GMT 2009


On Thu, Oct 29, 2009 at 12:53:45PM -0400, Adam Glauser wrote:
> John Whelan wrote:
> > Basically the map in Ottawa is unreliable but we don't know where.  
> > There seems to be no way of knowing whether a road has been mapped by 
> > GPS trace or sketched in by hand.
> 
> If I understand the process correctly, to do an import from Geobase you 
> would need to use a script 
> (http://wiki.openstreetmap.org/wiki/Geobase2osm) to convert the files 
> from Geobase to .osm files.

Although the conversion from geobase is a lot of work, it's already been done!
See
https://spreadsheets.google.com/ccc?key=0Am70fsptsPF2dG1ZN1YwMmZCVDhDOHZpbUNmOGlvWGc&hl=en&pli=1
In particular, the area
http://www.easy-share.com/1905429944/031G45.may29.osm.gz
covers Ottawa.

What I recommend when updating Openstreetmap is to use josm and
download the relevant openstreetmap data and gps traces (you already
uploaded your personal traces to openstreetmap, right?). Next, load
your local copy of the relevant geobase data. Then use your judgement
plus local knowledge as to how streets should be mapped.

One thing that seems to initially surprise people who have not used
GPS much is how bad a lot of GPS traces are. A good, modern GPS is
amazing when the skies are clear. However, use an old gps or add trees
or cloudy skies and you can suddenly find the traces weaving more than
a drunk driver.

*** BTW, if possible set your GPS to record at 1s intervals. ***

Until perfectly aligned, free, hi-resolution satellite imagery comes
along, every tool we have is flawed. Even then, satellite images can't
see through trees or clouds.

-- 
James Treacy
treacy at debian.org




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