[Openstreetmap] Tunnels

[Simon Hewison]

Andy Robinson wrote:
> Ok, so I am a tunnel engineer so I should have some ideas on how to map
> tunnels - but I don't. No gps down there of course. Let's see who can come
> up with the craziest ideas!

Compass (can lie if tunnel is steel-lined)
Altimeter (can lie is the tunnel is force-ventilated)
Odometer (pretty accurate, unless there's wheel slip)
Differential Odometers (can determine how much a vehicle is turning, and 
in which direction, but needs calibrating against a perfectly straight line)
Accelerometer (pretty accurate)
LIDAR surveying (can give very accurate details of curves in tunnel walls)
Theodolite/transit.

-- 
Simon Hewison