[Talk-ca] Import of large features in Canvec

[Sam Vekemans]

http://www.openstreetmap.org/browse/relation/393821

 attribution = Natural Resources Canada  canvec:CODE = 1240022  canvec:UUID
= cad1acc2f7794480a0c17cadeef4d3b7  natural = wood  source =
CanVec_Import_2009  type = multipolygon
That looks fine.  I would remove that canvec:UUID tag as since now it is in
the database it is free to edit, and to what we wish to.   But that's just
me.   BTW, in the USA Tiger data, the UUID was removed as it has a 'power
fit' where it was treated as more valuable than regular users edits.   That
part (power fit) is not acceptable with OpenStreetMap.

The canvec:sourceDate=* should be added (it available in the datasource)
since that tells the users how old the data is and gives them a way to
compare the data with their own datasets (ie. from municipalities directly)
or from physical observations.  Change on the ground happens so fast that
it's important to have it on all features.

Its worth no note that this 'wooded_area' is simply just that, it has no
boundaries, it just states "at the time of surveying, this area has trees,
and the wholes (inner polygons) dont have trees".
This 'wooded area' is not a designated area, so it's neithor a park/private
land/protected area.
When you look at the yahoo imagery (and future imagery) you can easily see
what the currently status of the 'wooded_area' actually is.  But on the
ground, you'll see what it's like today.

So in sum, when your out mapping, feel free to adjust the edges of these
polygons to accurately show where in fact the 'wooded_area' is today.   And
if you know what the designation of the area is. ie. signs that say park
area, you can add that in as an unfilled polygon border.

Great to see no edges, nice fix.

Cheers,
Sam


On Sun, Jan 24, 2010 at 7:59 PM, Frank Steggink <steggink at steggink.org>wrote:

> Hi all,
>
> Today I have (finally) worked on large features in Canvec data (forests,
> water, etc.), and I have come up with a method how to deal with them.
> This currently involves PostGIS, but maybe I'll use GEOS or another
> method, so that it isn't necessary to load data in a DB. More details
> will follow soon, since I need to clean up code / sort out things a bit,
> and eventually integrate it into the canvec_to_osm.py script.
>
> Right now I've uploaded (only) wooded areas in the Charlevoix region in
> Quebec. This already makes the map look entirely different! The result
> can be found here [1]. Changesets: [2] and [3].
>
> You'll see faint horizontal and vertical lines crisscrossing the area.
> This is an artifact of making the features smaller (0.1 x 0.05 degrees).
> This will be dealt with with the "gamma" option which is part of the new
> Mapnik 0.7.0 release. This will probably be used in a couple of weeks on
> osm.org. See [4] for more info.
>
> Cheers,
>
> Frank
>
> [1]
> http://www.openstreetmap.org/?lat=47.625&lon=-70.25&zoom=11&layers=B000FTFT
> [2] http://www.openstreetmap.org/browse/changeset/3707953
> [3] http://www.openstreetmap.org/browse/changeset/3708062
> [4] http://trac.mapnik.org/wiki/PolygonSymbolizer
>
>
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