Annoyingly it seems every time you scroll pass one of the maps a browser history entry is pushed
However, when you change the src attribute of an iframe, for some reason your browser creates a new history frame. I suppose so you can navigate inside of an iframe and go back/forward as expected.
The correct solution is to create/remove the entire iframe element instead of reassigning the src attribute.
See discussion at http://stackoverflow.com/questions/14737365/modify-iframe-sr...
You can see it in the HTML source of the page around the "check visibility every half-second, hide off-screen demos to go easy on the GPU" comment.
Here's one of our office: http://kespry-experiments.s3.amazonaws.com/elevation/valueFo...
I wrote a webapp hillmap.com that does client side slope shading for travel in avalanche terrain a few years ago using a usgs webservice that has since broken. I've looked into building a replacement but it is amazing how hard it is to find consistent elevation data across the globe.
Basically a nice article talking about how the data is gathered, stored, and sometimes used.
Is this a good way to farm karma or something?