[Openstreetmap] Tunnels

[Andy Robinson]

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!

Here's some more logical options, but not necessarily feasible!

1. From the surface using an array of acoustic devises to listen for
underground noise.
2. GPR (ground penetration radar) will work but not for deep tunnels
3. Tunnels with footways can be adequately "surveyed" with simple surveying
skills.
4. The outline of some tunnels which were constructed by open cut (top down)
can be seen from aerial photography.
5. Monitor tunnel collapses (very infrequent)!

Of course we could just draw a straight line from portal to portal as many
paper maps do!


Andy Robinson