The current state of the art of embedded motion sensing is based around micro-electromechanical systems (MEMS) devices. These miracles of microfabrication use tiny silicon structures, configured to detect acceleration and rotational position in three dimensions. Accumulate these accelerations and rotations, and you’ve got a device that can find its orientation and track movement without any external waypoints.
Why do we care about dead reckoning anyway? Surely GPS and related positioning systems are good enough? Above ground GPS is usually good enough, but underwater and underground this simply won’t work. Even heading indoors has a dramatic effect on the GPS signal strength, so yes, we need another way for some applications.
Right now, the current state of the art in portable sensors are MEMS devices, and you can get them for the cost of a hamburger. But if you want the ultimate in accuracy, you’ll want a quantum atomic interferometer. What that is, and how it will be possible to make one small enough to be useful, is half of the story. But first, let’s talk MEMS.
Fusion of The Sensors
Given an initial position and accumulated accelerations in 3D, it is possible to track position, for a short while at least. According to this (outdated) Cambridge University report on Inertial navigation systems, with a MEMS-based inertial tracking system, positional error can exceed 150 meters in under a minute, because the errors don’t average out, they accumulate.
Improvements can be made by fusing data from other sensors into the navigation model. It all depends on where you are; here on earth such additional data inputs could be taken from a magnetomet ..
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