Comment by dabreegster

abstreet.org has an offline import process that combines data from OpenStreetMap, city-specific GIS datasets, and elevation into a single file. The process has to be deterministic, given the same input and code, and calling out to an external API is a non-starter. We use https://github.com/eldang/elevation_lookups, a Python library that downloads missing LIDAR or SRTM data and uses GDAL to handle batch queries. Two issues with it are having too many dependencies (so we run it in Docker) and not being able to parallelize lookups without blowing up memory, due to some GDAL caching internals.