[Talk-us] NHD imports

Paul Norman penorman at mac.com
Sun Oct 28 23:05:07 GMT 2012

> From: Nathan Mixter [mailto:nmixter at gmail.com]
> Sent: Sunday, October 28, 2012 1:39 PM
> To: talk-us
> Subject: Re: [Talk-us] NHD imports
> In June, user Bsupnik converted the entire NHD dataset into OSM format.
> The files are available at http://bsupnik.dev.openstreetmap.org/NHD. He
> mentioned that he was working on creating better quality files. The
> files that he created look good. They are missing the names though. It
> looks like they just need a couple minor tweaks because the files
> generally looked good.
> Just wondering if any progress has been made. These would be ideal once
> the bugs are worked out so people could review and upload the data in
> their area.

I downloaded a random area (17010104) and looked at these.

There were no real OSM tags on the ways, only gnis:fcode, gnis:ftype,
nhd:com_id and source.

I'd question anyone proposing an import with both fcode and ftype because
ftype can be inferred from fcode.

Also, it suffers from an inherent limitation by splitting it up among
multiple files. This method loses the connections between the layers,
resulting in duplicate nodes and the topology not being connected. I looked
at a separate-layer approach when I first started looking at NHD and with
how NHD is structured with many interdependent layers it doesn't make sense
to do it that way. You have to merge all the layers together as a
multi-layer file and then convert to OSM. I'm not sure if shp-to-osm can
handle multi-layer sources.

A couple of other specific issues with these conversions:

- They're of 2011 data, not the latest NHD data

- I wasn't able to find a rules file from bsupnik for the conversion, so
they can't be rerun with latest data. He hasn't been active on the lists
since 2011 and hasn't replied

- The NHD data model changed since 2011

If anyone is aware of where the file with the rules bsupnik used resides,
please let me know. It would really help what I'm working on.

Also, needless to say, someone who wanted to import a basin would need to
read and follow http://wiki.openstreetmap.org/wiki/Import/Guidelines

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