[Talk-ca] British Columbia Coastlines
penorman at mac.com
Tue Feb 14 02:20:57 GMT 2012
I can't speak for the other areas in any great detail, but in the lower
mainland the GeoBase coastline isn't bad from what I've seen, it's just that
there have been active users improving the coastline from Bing imagery, or
higher quality imagery. In terms of data sources for the coastline, I know
that Surrey has good accuracy up to date data for all the waterways
(available as PDDL). Vancouver and North Vancouver might, but I haven't
investigated in any detail because their datasets are not available under an
If you're looking at priorities for water-related features, I'd suggest
streams as a higher priority. A lot of the streams in the NHN appear to be
paved over, although this may of improved since I last looked. I talked to a
friend who does urban stream cleanup work, and the cities are the only
potential datasource for more accurate data, the province doesn't have any.
> -----Original Message-----
> From: Bégin, Daniel [mailto:Daniel.Begin at RNCan-NRCan.gc.ca]
> Sent: Monday, February 13, 2012 6:00 AM
> To: Paul Norman; talk-ca at openstreetmap.org
> Subject: RE: [Talk-ca] British Columbia Coastlines
> Amazing task!
> And I understand that we should eventually have a look in Greater
> Vancouver, Victoria, Nanaimo and Sidney area for better data.
> -----Original Message-----
> From: Paul Norman [mailto:penorman at mac.com]
> Sent: February 13, 2012 03:00
> To: talk-ca at openstreetmap.org
> Subject: [Talk-ca] British Columbia Coastlines
> For the last couple of weeks I have been replacing the portions of the
> BC coastline which were PGS or CT-dirty imports with the latest
> CanVec/GeoBase data. I elected to use GeoBase since it's coastlines
> require less manual processing to get into workable form. This process
> is now finished, with the exception of the basins that are in the US and
> have data in GeoBase and the 08OA000 and 08OB000 basins (Haida Gwaii)
> which are in progress.
> Before replacing any coast, I compared it with the GeoBase data for
> accuracy. For most of BC's 25000 km of coastline the data was PGS data
> and easily replaced. The only places where there was substantial
> coastline retained were in Greater Vancouver, Victoria, Nanaimo and
> Sidney. The quality of the OSM coastline data exceeds that of
> GeoBase/CanVec in these areas.
> All the data was run through JOSM's simplify function with a max-error
> of 1.5m. On later runs, short ways were combined into larger ones after
> simplification. The search expression "(parent child selected | parent
> selected) nodes:-1000" was used in doing this.
> In the process I identified many unmapped rivers where I needed to join
> two sections of coastline together. Where bing imagery showed a river, I
> added a brief tracing. Most of the bing imagery was low-resolution
> Landsat or higher-resolution imagery from the BC government, the same as
> is found on their openmaps WMS server.
> In the process, I ran JOSM's validator tool over most of the coastline
> and fixed other unrelated errors.
> The .osm files were 232 MB on disk before simplification The total
> number of objects uploaded is approximately 1.5 million Surprisingly, no
> errors were found by coastcheck in the coastline, indicating my
> procedures worked There are 47 NHN basins with coastline, varying in
> complexity and size from 5k nodes before simplification to 150k nodes
> before simplification
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