Is a compass enough for turn-by-turn navigation in smart glasses?
No. A compass estimates heading, which is the direction a device points. Turn-by-turn navigation also needs position, a route and a way to associate your location with the next maneuver. Facing east does not tell the system which intersection you have reached.
Direction and position answer different questions
Heading can help orient a cue, but it cannot choose a route by itself. A route service needs a destination and map information; the application then needs updates about your progress. Head direction and travel direction can also differ when you look sideways while walking.
When a cue seems wrong, separate “the system thinks I am on the wrong street” from “the system has my location but points the cue incorrectly.” We use that distinction to narrow whether the problem concerns location, route state or orientation.