[Talk-us] [Imports] What to do with unnamed NHD streams

Clifford Snow clifford at snowandsnow.us
Mon Oct 29 05:32:33 GMT 2012

On Sun, Oct 28, 2012 at 8:51 PM, Paul Norman <penorman at mac.com> wrote:

> Background: I'm working on converting NHD to .osm format
> NHD is an extremely large data set. It's about 25G of zipfiles and all of
> this converted to .osm would total about 3 TB. This is about 10x-15x times
> the size of planet.osm.
> There are three factors that lead to this large size. The third is what
> this
> email is about
> 3. A lot of NHD is very minor streams "only of use to hydrologists." There
> are streams that you would be hard pressed to locate if you were there in
> person and in some cases they do not exist anymore.
> A sensible solution in any NHD translation may be to drop any FCode 46003
> (intermittent) streams without a name. It may also be worth dropping FCode
> 46006 (perennial) streams without a name.
> I've looked at a couple of regions with this adjustment made and they seem
> a
> lot more reasonable. The data is a lot more manageable and of more
> relevance
> to a general purpose map like OSM. There are also a lot fewer cases of
> streams that no longer exist.
> Does anyone have any thoughts on what should be done in a NHD translation
> with these streams?

What would be saved by dropping the nameless intermittent streams assuming
they were simplified? The area I'm working in, (mountainous) the
intermittent streams are typically spring snow melts. So until the snow
melts, the streams can be sizable. It would be of concern to hikers and the
forest service industry.

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