Transitology

This is a demo of my skills in Rust for potential employers. This is a public transit router, work in progress.

Parts already built:

• osmio2 -- reads OSM XML files and lets you iterate/map over objects
• graph -- OSM file to routing graph converter
• route -- router with A* and ALT algorithms implemented

osmio2

This is a library that can read and write .osm[.gz|.bz2] files. It's similar to osmio, but all shorthands don't crash, and it can handle .gz and .bz2 files seamlessly.

It gives you an iterator over all objects (with options to skip nodes/ways/relations) to save CPU cycles, and map_* shorthands.

Example: reading nodes and ways from an OSM file:

use osmio2::{reader::OsmXmlReader, objects::OsmObj};

fn main() -> Result<(), Box<dyn Error>> {
	let mut rd = OsmXmlReader::from_path("some-path.osm.gz")?;
	rd.skip_relations = true;

	for w in rd {
		match w? { // w is Result<OsmObj, ReadError>
			OsmObj::Way(way) => { println!("{:?}", way.nodes) },
			OsmObj::Node(node) => { println!("{:?}", node.id) },
			_ => {}
		}
	}
}

A simpler syntax to iterate over only one kind, ways:

let mut rd = OsmXmlReader::from_path("some-path.osm.gz")?;
rd.map_ways(|w| {
	println!("{:?}", way.nodes);
	Ok(())
})?;

It's parallelizeable with rayon.

graph

Converts OSM XML files into raw graph. Vertice of the graph are either intersections, or joints of roads of different types. The latter should be then contracted to reduce the number of edges and vertice in routing. At this stage, it ignores oneway tag.

Example output:

node1,node2,WKT,category,lanes
252613842,910721898,"LINESTRING(83.09475 54.85918, ... 83.097115 54.8574)",secondary,1
209908088,892761717,"LINESTRING(83.088135 54.83076, ... 83.094734 54.833687)",secondary,1
...

Geometry column is called WKT to make this easy to see in QGIS.

route

Implementation of "real" routing graph and algorithms on it. So far, these are just A-Star, and ALT.

Currently, it calculates shortest paths between routes and measures speed of the algorithms.

Usage:

$ cd graph
$ cargo run -r ../path-to-osm-file.osm.bz2 ../graph.csv
$ cd ../route
$ cargo run -r ../graph.csv ../route-result.csv

Results visualized in QGIS:

A* algorithm:

ALT algorithm:

Currently, routing is distance-based, and ALT doesn't have a big advantage over A*, just ~2x.