[Talk-us] Water Areas (NHD)

Christopher Schmidt crschmidt at metacarta.com
Mon Jan 12 01:36:04 GMT 2009

On Sat, Jan 10, 2009 at 09:47:20PM -0500, Christopher Schmidt wrote:
> On Sat, Jan 10, 2009 at 08:20:01PM -0600, Ian Dees wrote:
> > NHD data is accessible by going to the data viewer (http://nhdgeo.usgs.gov/),
> > then by clicking on the extract tool on the left and dragging a bounding box
> > to specify which subbasins you want the data for. A window will pop up where
> > you can specify that you want high-resolution data in Shapefile format.
> > Don't select the "fill in flowlines", put your e-mail in, and you'll get an
> > e-mail when its extracted.
> Wow. How... 'interesting'. :) Thanks; I've given a shot. I'll put
> together a WMS with both side by side and see the difference. Maybe bth
> will be needed, in the end. 

I ended up opening them in qgis.

 1. The data is almost exactly the same; there are a few cases where NHD 
    has an extra feature, none that I could see where the MassGIS data
    had an extra.

 2. The data matches the MassGIS data to at least 4 decimal places, and
    in most cases, as much as 6 or 7.

So, I think just giong with NHD is good. I've listed the subbasins I'm
likely going to be working on on the wiki. I'll start working on
converting a dataset and let the list know where I get to.     

Christopher Schmidt

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