[Talk-us] NHD data import question

[Ben Supnik]

Hi James,

> I've been checking some of the imported data and my general feel is that it is
> overdigitized.  I don't know if medium versus high reflects just the quality or
> the amount of digitization.  That would be something to check.  One could also
> just run some sort of simplification algorithm on all the data.

There are a lot of nodes. :-)

> Also, are the plans to make one file for each subbasin or one file per attribute
> (flowline, waterbody etc...).  With one file, one can remove all the duplicate
> nodes before uploading.

My plan was to create one .osm file per sub-basin x layer (the data 
comes in layers of areas, waterbodies, points, lines, and flow-lines). 
So we'd have five layers in separate files per sub-basin.  I _think_ 
merging that in .osm would be relatively straight forward, but it might 
be easier for users to cope with layered.

(Do we even...want flow lines?  The data is enormous, most of it isn't 
going to lead to map-visualizable things, and the 'value' of the data 
set, namely hydrological analysis, might not last long once the data is 
in OSM and the water network's hydrological properties aren't being 
enforced during edits.  Plus if only part of the flow lines are imported...)

> Maybe it would be useful to do a test subbasin with whatever toolchain you're
> going to use and then post it so that mappers can check to see how the
> conversion meshes with our general wants.

That's a good idea and should be straight forward.  I can post the 
medium and high-res sub-basins and let y'all compare.

cheers
ben
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