[Talk-us] NHD import

Gregory Arenius gregory at arenius.com
Mon Apr 9 07:25:03 BST 2012

Yes, I see a lot of water features that are just not corroborated by the
> aerial imagery, which could mean one of at least three things:
> 1) The aerial imagery is out of date
> 2) The NHD data is out of date
> 3) The NHD data represents something I don't understand (the future, a
> temporary situation (which should not be in OSM), something underground?)
Some of the water features in NHD are also seasonal, although that is
usually tagged in the data.   Also irrigation canals are often just ditches
and can be hard to identify from aerial imagery especially the smaller ones
as they aren't always in use.

The tags on a lot of those features have some gnis:type tags that say
ditch-canal or something like that but the OSM tag is just canal which
doesn't really do a great job describing the situation exactly.

I agree, though, the data you pointed out looks pretty odd, especially the
square shapes.

I'm surprised that NHD has data that includes irrigation ditches as small
as some of the ones noted above.  Anybody know how they gathered all of
that data?

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