[Talk-us] NHD import: what data quality is acceptable?

Kevin Kenny kkenny2 at nycap.rr.com
Mon Jul 23 12:47:40 BST 2012


On 07/22/2012 10:09 PM, Paul Norman wrote:
>> From: James Umbanhowar [mailto:jumbanho at gmail.com]
>> Sent: Sunday, July 22, 2012 6:43 PM
>> To: talk-us at openstreetmap.org
>> Subject: Re: [Talk-us] NHD import: what data quality is acceptable?
>>
>> On Sun, 2012-07-22 at 18:33 -0700, Paul Norman wrote:
>>
>>>
>>> The main weakness with NHD data that I find is that there is no way to
>>> distinguish between an OSM waterway=stream and waterway=river
>>>
>>
>> Why not use the name?
>
> The name is the best way I've found and is in fact what I'm using
> (https://github.com/pnorman/ogr2osm-translations/blob/69434ec55a48e9e4858ef3
> 5f2489949b2020e527/us_nhd.py#L234) but it's not 100%
>
> No way is perhaps a bit strong, no fully reliable way would be more
> accurate.

Using ArtificialPath comes awfully close around here. There are a lot
of things named 'creek', 'kill' or 'brook' around here that would be
surrounded by 'waterway=riverbank', and I would presume that anything
that rates having its banks drawn is already a 'river' according to
http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver . There are
also a number of tiny streams that would be tagged 'river' because
they are tradiitonally identified as rivers' headwaters. I say
"traditionally", because they often do not correctly identify the
longest reach of a given river. It would somewhat silly tagging
the "West Branch Neversink River" as a 'river' - it's quite a
minor stream. But by the same token, the Schoharie Creek, the
Catskill, the Kaaterskill, and the Esopus Creek are quite sizable
rivers whose flooding wiped out entire villages in Hurricane Irene.

I guess to some extent my local knowledge is coming into play, but
the features that the NHD curators have drawn areas around and
promoted to ArtificialPath are almost exactly the things that
I would label 'river.'

The reason for 'at least three nodes of ArtificialPath' is that it
eliminates most of the detritus where artificial paths are created to
join a tributary stream with a major river's centerline.

-- 
73 de ke9tv/2, Kevin



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