Route planner: Respect tunnels and brides for elevation sums
A quite tough problem when calculating elevation sums or charts of routes/tracks is if the route crosses bridges or crosses tunnels. In these sectors usually the (wrong) elevations of the terrain surfaces below the bridge (=river) or above the tunnel (=mountain) is taken into account - which can dramatically differ from the correct elevation of the street on the bridge or in the tunnel.
Thankfully the router "BRouter" (maybe also LoRouter in Locus 4 ?) is able to respect those 2 structures and calculates a linear elevation line from the beginning to the end of the tunnel/bridge - and not the elevation of the river below or mountain above.
But I noticed that these feature not always works: For example take the roads within tunnels on the westside of Lake Traunsee (N 47.8314°, E 13°.787902). There are 2 roads within tunnels, the Eastern one along the lakeside for hikers and bikes, the Western one for cars. Crossing the tunnels should result in elevation differences of about 0m. But if using BRoute Route planer, both roads take the elevation of the mountain above into account by mistake.
Another one is the crossing of river "Donau" in Linz (N48.3076°, E14.2853°). Should also be ca. 0m difference. This is true if I route via the eastern bicycle way. But not if I route over the main road for cars, where we can see a drop down to the elevation of river danube in the chart.
Do you have an idea how to solve this problem that Brouter's algorithm regarding bridges and tunnels just sometimes seem to work?
Btw: For testing I advice to use 1"-elevation files of https://sonny.4lima.de because they reduce errors because of rough 3"-resolutions of or wrong elevations of the SRTM files.