Flat maps have a hard time communicating elevation changes, but now you can access the data to visualize as you want. Google Maps added two elevation services, bringing you the meters above sea level for any point on earth.
You can play around with a mashup created by the Maps team using the new data at the end of the post, where I've embedded the tool. Be sure to check out Death Valley for some below sea level examples.
The service can be accessed with Google Maps V3, or via its own elevation web service, which returns JSON or XML. The latter gives you more freedom with how you use the data, but it's subject to the same terms as other map web services: you need to eventually plot the data on a Google Map. We've add a new Google Maps Elevation API profile with more details.
Finding elevation along a route has long been part of the GMap Pedometer, a classic mashup for walkers, runners and bikers. In fact, there are several end-user tools that make use of elevation data in our 6 Fun Sites to Track Your Trails. Now, getting at that data is even easier.
There's also a simple code sample for incorporating elevation directly into your Maps. Keep in mind this only works for V3. Previously Google had pitched the latest version of its Maps API as mobile-specific. By adding elevation to V3 and not V2, they could either be signaling that V3 is the way forward or that elevation data is of more use to users on the go.
via Mike Melanson