Wikipedia
GraphHopper is an open source road routing library and server written in Java and provides a web interface called GraphHopper Maps. As well as a routing API over HTTP. It runs on the server, desktop, Android, iOS or Raspberry Pi. By default OpenStreetMap data for the road network and elevation data from the Shuttle Radar Topography Mission is used.
GraphHopper can be configured to use different algorithms such as Dijkstra, A* and its bidirectional versions. To make routing fast enough for long paths (continental size) and avoid heuristical approaches GraphHopper uses Contraction Hierarchies by default. In the Java Magazine from Oracle the author Peter Karich describes the techniques necessary to make the system memory efficient and fast. Furthermore, GraphHopper is built on a large test suite including unit, integration and load tests.
The Apache License allows everyone to customize and integrate GraphHopper in free or commercial products, and together with the query speed and OpenStreetMap data this makes GraphHopper a possible alternative to existing routing services and GPS navigation software.
Besides point-to-point routing for different vehicles GraphHopper can be used to calculate distance matrices which are then used as an input for Vehicle routing problems. Other use cases are:
- Track vehicles via map matching - i.e. 'snap' real world GPS points to digital road network
- Assist urban planning
- Traffic simulation
- Isochrone calculation - i.e. determining the reachability for cars, pedestrians or bikes
- Indoor routing like for warehouse optimizations or tradeshow planning
- Eco-efficient routing
- Virtual reality games like Scotland Yard