Fascinating article in New Scientist about a possible ‘quantum positioning system’ soon to be tested in submarines.
GPS doesn’t work under water so submarines rely on fancy accelerometers to calculate where they have gone since their last accurate fix on the surface. But this sophisticated form of ‘dead reckoning’ is still far from perfect. After a day the ‘drift’ may exceed one kilometre.
The UK Defence Science and Technology Lab (DSTL) is now developing an enhanced acceleromter relying on the perturbations in clouds of atoms trapped and super-cooled by lasers. If this can be made to work it may yield positions 1000-times more accurate than conventional accelerometers.
There are plans to test such a system at sea in 2016. But one factor that will need to be taken into account is the gravitational anomalies caused by undersea mountains. So improved maps of gravitational variations will be needed.