[Talk-us] NHD conversions to OSM

[Phil! Gold]

* Josh Doe <josh at joshdoe.com> [2011-06-09 15:43 -0400]:
> I suppose one of the waterway=stream's should be changed to
> waterway=river, and only one of the waterway=riverbank objects should be
> used.

Ian covered the medium/high and area/flowline difference already.  As for
the waterway=river issue, the NHD doesn't make a distinction between
waterway=stream and waterway=river the way OSM does.  If a waterway is
wide enough, it gets represented in the area tables with FCode 46006,
which we map to waterway=riverbank, and in the flowline tables with FCode
55800 (ARTIFICAL PATH), which we map to waterway=stream[0].  If there's no
representation in the area tables, a waterway with year-round flowing
water gets FCode 46006 in the flowline tables, regardless of its width.

Basically, OSM draws different distinctions among waterways than the NHD
does, so no mapping between the two tagging systems is going to be correct
in all cases.


[0] And we can't just map all 55800 FCodes to waterway=river because the
    same FCode is used *anywhere* a waterway flows through a wider area of
    water, including things like streams that flow in and out of ponds.

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