What makes tunnels so difficult to detect?
In: Technology
These two things are completely different, so we can’t really compare the technologies used.
To detect a tunnel you will need to send some kind of “pulse” into the ground, and detect a return. In the air we use radar (electromagnetic waves) but these don’t travel well in the ground.
So for the ground we usually use sound, which is also what we use under water. The sound travels until the ground material changes, at which point some of the sound will reflect (and we can detect the reflection) and some continues downwards. By measuring the time and ‘shape’ of the reflected sound we can make a good guess at the depth, and what materials are there.
So we can detect tunnels with this method in theory. The problem is that this kind of sound-based imaging has a very bad resolution. This means that it would be very easy to miss a small tunnel if it is more than a few meters deep.
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