Did you know, that you can even calculate the elevation profile when planning a route with Google Maps? Isn't it at least as important for a cyclist, as the length of the route? I was surprised to see the elevation graph of a bike trip along the Adriatic seeside, having almost the same amount of total ascent like crossing Switzerland from Bodensee to Zermatt, through some of the highest mountain passes of the Alps...
So, how to get the elevation profile of a route? Today, Google does not provide an integrated solution. However, the information basis is public, called SRTM. We just need some further free web services to complete our latitude and longitude data with altitude values. Let's see the step-by-step guide:
- Plan the route with Google Maps
- Export the route to a KML file by copying the URL of the plan using the Link option, than pasting it into the cool and free http://www.nearby.org.uk/multi-to-kml.php
- Copmlete the KML with altitude data by uploading the KML generated in step 2 into www.gpsvisualizer.com/map?output_googleearth
- Save the new KML that already holds altitude values for each waypoint of the route
You can visualize the elevation either at gpsvisualizer's, or at www.everytrail.com.
But, how accurate is this SRTM model? Actually, I did a test. I took a GPS track log already containing altitude data, then I let gpsvisualizer.com
overwrite the altitude with data from SRTM. The total elevation of the original file was 1270m, while the one profiled by SRTM shows 1370m.
The difference is less than 8%. That's fair, I believe. See both diagrams above