Algorithms Shortest Path
Data Source: Stadt Wien – data.wien.gv.at
Shortest Path (Point to Point)
This algorithm implements the Dijkstra search to return the shortest path between two points on a given network dataset. The special feature of the QNEAT implementation is that it accounts for points that don't sit exactly on the network (non-network-elements) and calculates separate entry- and exit-costs for them. The geometry of the path is not limited to on-network travel but includes the first leg (entry leg) and last leg (exit leg) between the origin and destination points and their respective counterparts on the network. Distances are measured accounting for ellipsoids.
As of QNEAT 4.0, entry/exit costs are always calculated ellipsoidally using the network layer's own CRS ellipsoid — the old "Entry Cost calculation method" parameter (Ellipsoidal/Planar) has been removed. See Changes from QNEAT3.
| # | Mandatory Parameters | Type | Info |
|---|---|---|---|
| 1 | Network layer | Vector Layer | Geometry type must be LineString |
| 2 | Origin point (x, y) | Coordinate pair | obtain by clicking on map canvas |
| 3 | Destination point (x, y) | Coordinate pair | obtain by clicking on map canvas |
| 4 | Optimization criterion | Shortest path (distance) | Fastest path (time) | - |
| 5 | Shortest path layer | Output Vector Layer | Attributes: start_id, start_coordinates, start_entry_cost, end_id, end_coordinates, end_exit_cost, cost_on_graph, total_cost |
| # | Optional Parameters | Type | Info |
|---|---|---|---|
| 1 | Direction field | Field containing direction values | - |
| 2 | Value for forward direction | user input | input must be referenced to Direction field |
| 3 | Value for backward direction | user input | input must be referenced to Direction field |
| 4 | Value for both directions | user input | input must be referenced to Direction field |
| 5 | Default direction | Forward direction | Backward direction | Both directions | used when no direction field is set, or a feature's direction value doesn't match any of the above |
| 6 | Speed field | Field containing speed values | must be numerical |
| 7 | Default speed (km/h) | user input | (!) sets network entry- and exit-speed |
| 8 | Topology tolerance | user input | Tolerate gaps in network (crs units) |