[UCANSEE2]

some of the newer steerable drilling assemblies, the odds are far greater than they would have been only a decade ago.

These 'drills' are equipped with a 'homing device'. They target in on the magnetic field of the pipe casing.

[Smokin' Joe]

I am unaware of magnetic sensors, but there may be some aside from the normal survey tools. But come to think of it, those are affected by casing, and may well serve as a close proximity steering aid.