BRouter: Elevation algorithm
Elevation awareness is the most important issue in bike routing if not routing in a flat country.
But in most routing software, elevation is either not handled at all or in a way that is not really
Even worse, most tools do not even report on elevation in a useful manner. The far-too-high
"total climbs" usually reported do not only accumulate real, small height-variations that
are averaged-out by the bikers momentum - they accumulate also noise and grid-interpolation errors
from the elevation data source.
BRouter uses elevation data from the Shuttle Radar Topography Mission (SRTM),
precisely the hole-filled Version 4.1 Data provided by srtm.csi.cgiar.org,
which is the data that is displayed e.g. in Google Earth and which is used in most elevation-enabled
routing tools. However, the routing algorithm is able to extract the information on real ascends and descends and
ignores the noise.
See the section about crossing the alpes for real examples.
On the reporting side, BRouter uses a similar concept to compute the "filtered ascend", which is
the ascend without the noise and the small hills and which turned out to be a valid concept
to estimate the real elevation penalty.