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Subject:        Re: MAPS-L: U.S. county-level relief data
Date:   Wed, 21 Dec 2005
From:   [log in to unmask] <[log in to unmask]>
To:     [log in to unmask]


Actually no.  What I often use is a Digital Elevation Model put out by the National Geophysical Data Center (30 second pixels, about 1 km) -- although there are some more intense ones online (USGS) as well. Then I make a grid of the same resolution (with values of the grid equal to the county FIPS) and then do things like:

zonalmin()
zonalmax()
zonalmean()

But remember this is a DEM -- there can be a whole lot of variation within that square kilometer.

Even if you download the 30m x 30m DEM by USGS, there can still be a lot of variation within that pixel -- also remember these data were collected by weary photointerpreters running stereoscopes and such (actually I'm not sure about that but I used to do it) --  If you truly want the highest elevation and lowest elevation by county, remember to add and subtract fudge factors.  The World Almanac has high and low elevations by state.  If you're just looking for a pretty picture, you're done.

The National Wetlands Inventory has digital coverages/shapefiles of wetlands.

Joe McCollum
FIA
Knoxville, TN




-- "Angie Cope, AGSL" <[log in to unmask]> wrote:
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Subject:        U.S. county-level relief data
Date:   Wed, 21 Dec 2005
From:   Christopher Winters <[log in to unmask]>
To:     Maps, Air Photo & Geospatial Systems Forum <[log in to unmask]>




A patron here is looking for a county-level data set for the U.S. that
contains

[1] mean altitude
[2] highest point
[3] lowest point
[4] percent area covered by swamp (wetland)

This (or the first three anyway) ought to be easy, but ...!

Any help would be greatly appreciated--many thanks.

Chris Winters
Bibliographer for Maps
University of Chicago Library



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