Navigation.js specification

#Purpose

The goal of this specification is to outline the rules and ideas this library adheres to guide a user along a route.

#Units

By default, the metric system should be used where available.

#Concepts

Navigation.js looks at a single step along a greater route. All calculations are done against this step and not against the whole route. Once a step is completed, the next step on the route can be compared. If the user is no longer on the current step, the developer should re-route the user and also set their internal step counter back to 0. The developer is required to keep track of the current step at all times.

#Re-routing

If at any time the user is not within 45 meters of any point on the current step, re-route the user.

#Completing a step

• If the user is within 15 meters of the end of the step, the user has completed the current step.
• If the bearing for the user is available, the above point must be true and also the users bearing must be within 20 degrees of the exit bearing of the step.

#Alerting the user

There are 2 types of alerts and both are of type boolean. These alerts are given distance along the current step based and by default are false.

Navigation.js has an alertUserLevel object with two keys on it:

• low
• high

When to alert

• A low alert is true when the user is within 1.5km of the end of the route and the step length is greater than 1.5km.
• A high alert is true when the user is within 45m of the end of the route and the step length is greater than 45km.