Snap tolerance parameter

[BK01]

Current state:
The BC Route Planner will compute a route along the road network to (or parallel to) coordinates within 1km of the road centre-line [MAX_SNAP_DISTANCE = 1000].

Test case: Destination is approx 1.2km from the road.
https://router.api.gov.bc.ca/directions.json?points=-123.14517%2C49.70719%2C-123.12172%2C49.68690&snapDistance=1200

Future state:

• Provide a parameter to enable developers to override that number by providing a new value in metres (snapDistance=1200).

[cmhodgson]

We never discussed the name of the parameter, but I went with the initial suggestion "snapDistance" - this is a request parameter than can be set for each request. I also setup an application-level configuration parameter called defaultSnapDistance which can be changed using the config UI or editing the configuration files, this sets the default value of the snapDistance parameter if no value is specified in the request.

[cmhodgson]

Note that the existing "demo" support for 511 events now uses the defaultSnapDistance config parameter as a limit for how far events can be from segments and still be attached to them. The existing demo 511 event file contains only very close matches so this tolerance isn't really used at this time.

[BK01]

Validated in BC Route Planner 2.2 (router-dev.api.gov.bc.ca) on Dec 19, 2023. Test case above used with a distance of 1000m (no route found) and 1200m (route found)