[OSM-talk] Argh, Canvec imports

[Frank Steggink]

On 17-11-2011 16:54, Michal Migurski wrote:
> On Nov 17, 2011, at 6:46 AM, Frank Steggink wrote:
>
>> Quoting Michal Migurski<mike at stamen.com>:
>>
>>> A cry of frustration:
>>>
>>> I do bimonthly runs of the worldwide coastlines  (http://metro.teczno.com/#coastline), and Canada seems to be a  recurring source of problems. What the heck is going on up there? I  consistently see new imports of what seems to be Canvec data  screwing up coastlines and making for some deeply broken renders:
>>>
>>> 	http://mike.teczno.com/img/broken-coast.png
>> Hi Michal,
>>
>> The rendering error northeast of Quebec City was caused by a novice user who has adjusted the Canvec data which was already there. The import in this region was done by me about half a year ago.
>>
>> The user in question had adjusted the coastline tags to waterway=riverbank, in order for him to show it up properly on his GPS (while using mkgmap for the conversion). He already became aware of what he has done, and has fixed the error himself (which I think is laudable). I've done a check, and the coastline looks all right to me. I'm not sure what to do with the remaining waterway=riverbank tag. This is part of a larger discussion about what to do with large waterbodies.
>>
>> The slippy map doesn't show the corrected situation yet, because the coastline shapefile is not updated very often.
>
> I had noticed a lot of waterway=riverbank up there, you're right.
>
> The first black and white image I link above is derived from the current, November 10 planet dump, so it's a very recent picture of coastline errors. Many of those errors didn't exist in the coastline I made from the November 3 planet dump.
>
> Here are some sample locations in Canada where the checker has found errors:
> 	http://www.openstreetmap.org/?lat=58.790035&lon=-94.202604&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=56.749700&lon=-92.698650&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=45.260826&lon=-66.086208&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=45.298267&lon=-66.117219&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=56.970073&lon=-92.627314&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=47.086208&lon=-70.745529&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=57.053591&lon=-92.000000&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=45.238757&lon=-66.055341&zoom=17&layers=M
> 	http://www.openstreetmap.org/?lat=44.936914&lon=-74.704294&zoom=17&layers=M
>
> -mike.
>
> ----------------------------------------------------------------
> michal migurski- mike at stamen.com
>                   415.558.1610
>
>
>
>
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I've fixed some coastline issues at the Nelson River / Hayes River 
mouths in the Hudson Bay, see [1]. There were some duplicated 
coastlines, and an "inland" island (which was running the wrong way). 
Near Churchill, MB [2] the coastline was already fixed by the Canvec 
import user a few days ago. I didn't see any coastline mistakes there. 
However, the treatment of "intermittent" water is far from perfect, and 
not how I would have done it. I'd rather convert it to natural=wetland, 
wetland = tidalflat, indicating that mudflats show up at low tide. Doing 
this along the entire Canadian coastline, which is very extensive, is a 
tough task. The coastline is really peculiar in some places, like here: 
[3], so I'm afraid we haven't seen the last error. Tools assisting us in 
error checks would be great, and absolutely necessary in the Canadian case.

Frank

[1] http://www.openstreetmap.org/browse/changeset/9856941
[2] http://osm.org/go/W6dBGeK-
[3] http://osm.org/go/W7CeaB