So this was interesting.
Downer are about to do some street surface repairs close to our place, where underground water has collapsed the road seal (something I first started reporting to Wellington City Council 18 months ago - but that's another story). Anyway Downer are there today spraying out the area to be excavated and in addition to using the usual CAT locator devices, there was a guy using divining rods and spraying marks in appropriate places - presumably to locate either water pipes or underground water. Quite the mix of "technologies" there...