On Sat, 02 Mar 2002 07:03:10 -0500, Timothy R. Cook wrote:
> Ron Parker wrote:
>> Nothing, really, except that DEM data is already rasterized and has a
>> better vertical resolution.  These days, topo data is often derived from
>> DEM data.
> 
> I just downloaded file at http://edcdaac.usgs.gov/gtopo30/w100n40.html
> How do I convert to dxf or raw or something else I can easily get into

If you really want something that's near 40N 100W you can get better-quality
data than gtopo from USGS; unfortunately the appropriate server seems to be
down at the moment, so I can't get you a URL.  But what you want is a 7.5-
minute DEM (Digital Elevation Model).  There are utilities to convert that
to a TGA, which you can then use as a heightfield.

-- 
#macro R(P)z+_(P)_(P)_(P+1)_(P+1)+z#end#macro Q(C,T)bicubic_patch{type 1u_steps
6v_steps 6R(1)R(3)R(5)R(7)pigment{rgb z}}#end#macro _(Y)#local X=asc(substr(C,Y
,1))-65;<T+mod(X,4)div(X,4)9>-2#end#macro O(T)Q("ABEFUQWS",T)Q("WSXTLOJN",T)#
end O(0)O(3)Q("JNKLCGCD",0)light_source{x 1}// ron### [at] povrayorg

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