GeoTIFF support, to improve bicycle and pedestrian routing

[kresp0]

OTP supports adding a GeoTIFF with elevation data. This enables better routes for bicycles and pedestrians. Except in flat areas of course :)

It could be as easy as adding the Digital Elevation Model as a GeoTIFF file with the .tif extension and the area as name. Ex: Amsterdam.tif

If OTP finds a .tif or .tiff file on the base directory, it uses this data while building the graph. I'm currently using it on bici.madrid with a 2m resolution DEM and it works nicely.

[ellenhp]

Currently walking and cycling requests are routed to Valhalla, not OTP. But Valhalla supports elevation as well so I think it makes sense to try and do this.

I was actually offered access to preprocessed global elevation dataset which could be convenient. I suppose I could go download it and cut it up with GDAL then reupload it to R2. I'd like to make it easy to support arbitrary areas though which might be difficult.