Evan Roberts asks,
Why do you think Google hasn’t integrated USGS topographic quads as a layer in Google Earth? Not enough of a demand? Not relevant to its business model? Don’t want to step on the toes of GPS partners? I’ve seen examples of users’ attempts to overlay topo in GE and, combined with the “Terrain” layer, the results can be fantastic! Any thoughts?
It’s an interesting question, in that (1) I thought that USGS data was freely available and (2) the terrain layer is fantastic in and of itself, but with a topo map overlay would be better still. Though it’s probably unanswerable in terms of “why isn’t Google doing this?” The bottom line is: the data is available, though not as a default — and once you load a layer in, the difference between Google’s layers and third-party layers isn’t really noticeable, is it?
I am aware of a few relevant links. A few days after Evan wrote in with his question, I got an e-mail from Matt Fox about his archive of historical topo maps for Google Earth: “The Google Earth Map Archive contains over 500 Historic USGS Topographic Maps for Google Earth. The maps date back to the late 1800s and right now are mostly for California, but more maps are being added all the time.”
There’s also some material on acquiring topo map raster images to use in Google Earth: this post on Ogle Earth points to a few sources; this post on Google Earth Blog points to a method of creating image overlays.
Finally, though it’s for Google Maps rather than Earth, BackcountryMaps is a mashup that integrates USGS topo maps and aerial data with the Google Maps API.