Does anyone have experience calculating total elevation gain for various rides, especially as related to the statistics provided by Topo USA 6.0? I am the coordinator for the upcoming 8th annual Country Coast Classic century out of Cambria, CA. I have used Topo USA 6.0 to describe the route. The program gives very accurate total ride distances, and accurately depicts the elevations along the route (summits, etc.). But the calculated 'total elevation gain' is roughly twice what my cycling buddies get with their on board computers (one a VDO) when they ride the course. The on board computers do some averaging based on atmospheric pressure changes, I'm sure. What data should I trust? Or, what is the source of data others use when describing a route to prospective riders?