Is the idea here to accurately track the acceleration that the sensor is undergoing? So, if you started at a known location with velocity=0 and integrate the acceleration data wrt time twice, you get the relative change in position and can thus know your new location?
“The aim of the Imperial College project […] is to create a device that […] does not rely on receiving external signals.”
and
“At the heart of the quantum compass – which could be ready for widespread use in a few years – is a device known as an accelerometer that can measure how an object’s velocity changes”
I wonder whether they really don’t use external signals at all or occasionally use them to correct for accumulation of errors. For example, the ability to detect that velocity w.r.t. earth is zero would help with that.
(Of course, for the London subway, the fact that trains tend to follow the tracks can help, if the system knows the track layout. That probably is the simplest way to prevent accumulation of errors, but then, do they really need such a complex accelerometer?)
My guess is that calculating the initial velocity is hard, so it will drift slowly. Perhapa keep the device on a table for a minute to ensure v=0, or sync it at every subway stop.
