Create a script for enriching graphs with height data

[leo-desbureaux-tellae]

Following #37, we encountered the need of height data on our graphs.

One source for such data is EU-DEM, that provides a file containing height data (raster) for European countries with a good precision. The format used is TIF.

Proposition

Create a script that enriches a given graph with height data from a given TIF file. Maybe add an option to the generate_osm_graph script to enrich the OSM graph after extracting it.

[leo-desbureaux-tellae]

See the new add_node_elevations_raster function of OSMnx 1.1.0 here