A colleague pointed out this postfrom Doug McCune's blog which experiments with visualizations of located quantities using elevation models. This approach is a little more on the artistic side rather than of high utility (it is, afterall, a height map, not a heat map).
Compare this with alternate views.
[Note, Doug McCune worked at Spatial Key, an innovative visualization company. He passed away earlier this year.]


For being dead, Doug's sure active on Twitter:
http://twitter.com/dougmccune
You may have missed the date on that blog post...
Posted by: twitter.com/petewarden | October 06, 2010 at 12:32 PM
+1 @petewarden
See also:
> http://twitter.com/dougmccune/status/11457337512
and
> http://rjria.blogspot.com/2010/09/doug-mccune-is-not-dead.html
Posted by: Fbahr | October 07, 2010 at 05:41 AM