fossyant said:
It depends on the terrain (and the program/data).
From experience Bikely underestimates by 25% in rolling terrain. In London it can overestimate wildly.
In very hilly terrain, especially if the road passes along the side of a valley or along a gorge with steep sides, it can overestimate wildly.
Various programs use different DEM data and models, none of which will be accurate as, by definition, they're a model of the terrain, not a perfect representation of it.
GPS plots are quite accurate, but you need to be careful to remove the obvious calibration problems, flutter due to poor signals, etc.
Finally, there's the definition of "climb". My commute follows the Thames and, bar a couple of bridges over it, rarely goes 5m above sea level and with no hills at all. Yet bikely, mapmyride, and my GPS all claim over 50m of climbing.
There's a 10m "climb" in Richmond Park (just past Ham Gate going anti-clockwise) that, if you get an uninterrupted run at, hardly takes any effort to get up as your momentum does most of the job. Further round there's a whopping 4m "climb" between Kingston and Roehampton Gates that is much more work since you can't carry enough momentum into it to clear it. The latter feels like more climbing, but is much less height wise.
Don't get hung up on climbing, unless it's something big in which case you can just look at the height at the bottom, and at the top on an OS map.
Rides are one of: pan-flat, flat, easy, undulating, rolling, hilly, challenging, epic or brutal.
These often change over time, despite the topography not changing one bit. Stuff that I found challenging two years ago now barely registers as undulating.
