-------- Original Message --------
Subject:        Re: RE: MAPS-L: U.S. county-level relief data
Date:   Fri, 06 Jan 2006
From:   Mike Flannigan <[log in to unmask]>
To:     Maps, Air Photo & Geospatial Systems Forum <[log in to unmask]>







Yeah, after thinking about it for a while I decided to forget
about GNIS and go straight to the benchmarks.  I thought
they would have a benchmark at the highest place in the
county, but now I suspect that is not true.  I quickly
downloaded Platte county MO benchmarks and found
the highest "dynamic ht" was 947.16 ft.  The benchmark
was reportedly here:
http://www.topozone.com/map.asp?lat=39.39944&lon=-94.86333&datum=NAD27&s=50&size=l

You can see elevations up to 972 ft right on that map.

Now I've decided that DEMs (digital elevation models)
are the way to go.  Of course you need the county
outlines for the whole USA.  On another GIS list
I am on we are working on those right now.  The
DEMS and county outline data are freely available
for the USA (I think), but finding the data is another
matter.

I'm going to do the county outline data because I
want it for other applications.  I'll leave the DEM
data to others, because like I say - I'm only mildly
interested in these high points.  Will probably get
to it someday, but probably not now.


Mike Flannigan


On Tue, 3 Jan 2006, [log in to unmask] wrote:
>Subject:        RE: MAPS-L: U.S. county-level relief data
>Date:   Tue, 3 Jan 2006 10:27:00 -0500
>From:   Zellmer, Linda R <[log in to unmask]>
>To:     Maps, Air Photo & Geospatial Systems Forum <[log in to unmask]>
>
>
>Hello,
>
>After getting two such questions in the space of a month (what is the
>highest point in [NAME OF COUNTY]), I started compiling them for
>Indiana. I have not gotten very far, as I have found that one must not
>only look at the elevations in GNIS, you also have to look for
>elevations of benchmarks
>(http://www.ngs.noaa.gov/cgi-bin/datasheet.prl).
>
>When I first started out, I found 3 high points that GNIS said were in
>Monroe County, Indiana that were not actually in Monroe County, Indiana
>(and submitted corrections for these to the USGS people who oversee
>GNIS). When I finally figured out what GNIS said was the highest point
>in Monroe County, I then tried to confirm it using topographic maps. The
>highest point was 2 topo quads away from the highest point listed in
>GNIS.
>
>Needless to say, this is a project that is slowly evolving. I am also
>using it as a training exercise for our students (they get practice
>using GNIS and look at topo maps).
>
>Finally, this is NOT a project that can be done using topographic maps
>online. Agencies that think electronic is just as good as paper need to
>reread the second paragraph (The highest point was 2 topo quads away
>from the highest point listed in GNIS.)
>
>This would be much easier in Arizona (15 counties) or Wyoming (23)
>rather than Indiana, which has over 90 counties. However, once finished
>I will post it on a web page. Linda Zellmer
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Linda Zellmer



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