From OSM to RawMap (convert_osm crate)

The first phase of map building reads in data from OSM files and a few others, producing a serialized RawMap. Importing all maps (one for each pre-defined bounding polygon) takes a few minutes. Players don't see this cost; it only takes a few seconds to load a serialized map.

• osm.rs: Read .osm, extracting the points for road-like ways, buildings, and areas
  • Areas usually come from a relation of multiple ways, with the points out of order. Gluing all the points together fails when the .osm has some ways clipped out. In that case, try to trace along the map boundary if the partial area intersects the boundary in a clear way. Otherwise, just use a straight line to try to close off the polygon.
  • Also read traffic signal locations and turn restrictions between OSM ways
• split_ways.rs: Split OSM ways into road segments
  • OSM ways cross many intersections, so treat points with multiple ways and the points at the beginning and end of a way as intersections, then split the way into road segments between two intersections.
  • This phase remembers which road segment is the beginning and end of the OSM way, for per-lane turn restrictions later
  • Apply turn restrictions between roads here. Since OSM ways cross many intersections, the turn restrictions only apply to one particular road segment that gets created from the way. Make sure the destination of the restriction is actually incident to a particular source road.
• clip.rs: Clip the map to the boundary polygon
  • Osmosis options in import.sh preserve ways that cross the boundary
  • Trim roads that cross the boundary. There may be cases where a road dips out of bounds, then immediately comes back in. Disconnecting it isn't ideal, but it's better to manually tune the boundary polygon when this happens than try to preserve lots of out-of-bounds geometry.
  • Area polygons are intersected with the boundary polygon using the clipping crate
• lib.rs: Remove cul-de-sacs (roads that begin and end at the same intersection), because they mess up parking hints and pathfinding.
• lib.rs: Apply parking hints from a King County GIS blockface dataset
  • Match each blockface to the nearest edge of a road
  • Interpret the metadata to assign on-street parking there or not
• lib.rs: Apply offstreet parking hints from a King County GIS dataset
  • Match each point to the building containing it, plumbing through the number of spots
• lib.rs: Disabled: Apply sidewalk presence hints from a King County GIS dataset
  • Match each sidewalk line to the nearest edge of a road
  • Update the road to have a sidewalk on none, one, or both sides
• lib.rs using the srtm module: Load (extremely poor quality) elevation data