3.5.2 · Survey a Cave
On the Way
The readout, snapping, the surface and rescue.
The readout: What each message means, from NO NORTH to AT.
Going: the target, the distance along the route and the height to climb or drop, then the line the route follows (VIA), the next station and its distance, and the bearing. Without north there's no bearing: it says NO NORTH. Off the survey it says REJOIN; with no route at all, NO SURVEY ROUTE and the straight bearing. Within 3 m the phone buzzes and the readout says AT.
Snap on the way: Small drift adds up; fix it as you go.
The Navigator drifts a little as you walk. Snap at stations you pass (Snap to a station) to keep your position honest, and before you start a new line.
On the surface: Finds pins topside, on or off a line.
The hike map has Go too, for pins: on a line shown on the map the route follows it; otherwise a dotted line runs straight there. See Hike Pins.
Rescue: When someone is hurt underground.
The same routing gives the way out from any point and the way back to an injured caver. See Rescue.