---------- Forwarded message ----------
Date: Sun, 27 Aug 2000 02:20:41 CDT
From: Joseph McCollum <[log in to unmask]>
To: [log in to unmask]
Subject: Re: Reference Question Regarding Elevations (fwd)

Get the DEM from the National Geophysical Data Center.
Also they have a county mask.

It would require some coding, but basically it is this:

high = zeros(3200);     /* there are something like 3200 counties in
the USA */
low = 10000 * ones(3200);
all = zeros(3200);
count = zeros(3200);
for i = 1:rows,
   for j = 1:cols,
       c = county(i,j);
       e = elev(i,j);
       if e > high(c);  high(c) = e;    endif;
       if e < low(c);   low(c) = e;     endif;
       all(c) = sum(all(c),e);
        count(c) = sum(count(c),1);
   end;
end;
avg = all/count;

This would not get the actual high elevation (or actual low) elevation in
each county.    It would get the highest (or lowest) - valued DEM pixel
(itself an average).