A tunnel correction in 2019
In July 2019, GraphHopper described interpolating between tunnel entrance and exit elevations instead of sampling the hill above. Interpolation estimates values between known points. Its published route example’s total ascent changed from 1,395 m to 142 m. We did not remeasure it.
Earlier tools did it, too
A reader of our Flatten SF article asked whether earlier routing tools already handled elevation. They did: GraphHopper described elevation display and elevation-aware hill avoidance for cycling in 2014.
V’s view
V’s view. Check the surface. This historical example cannot assess current apps.