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> Quantum sensors for PNT use atomic accelerometers or gyroscopes There is one fundamental problem with using any sensors for global positioning: a stationary

by nuccy 5y ago

> Quantum sensors for PNT use atomic accelerometers or gyroscopes There is one fundamental problem with using any sensors for global positioning: a stationary frame of reference is indistinguishable from the one moving with a constant speed on a straight (actually geodesic [2]) line (inertial frame of reference, general principle of relativity [1]). So accelerometers and gyros indeed can give you accurate orientation and acceleration/deceleration data, but they will inevitably accumulate uncertainty for long eventless movements, so use of GPS will be needed to occasionally calibrate the true position. The obvious options is to augment this data with readings of wheels rotational, airspeed sensors, radars, etc, then such systems may last even longer without cross-calibration with GPS. 1. https://en.m.wikipedia.org/wiki/Principle_of_relativity https://en.m.wikipedia.org/wiki/Principle_of_relativity 2. https://en.m.wikipedia.org/wiki/Geodesics_in_general_relativity https://en.m.wikipedia.org/wiki/Geodesics_in_general_relativ...

dtgriscom 5y ago
> they will inevitably accumulate uncertainty for long eventless movements Actually, they constantly accumulate uncertainty; no change in motion required.
- nuccy 5y ago
  True, but what you describe is related to the measurement and sampling accuracy. Until such sensors hit the Heisenberg uncertainty levels of precision on the readout/sensing, such uncertainties may be decreased further, there is no physical constrain on that (more sensors may help with that also). While it is in principle physically impossible to even identify the fact of movement linearly with constant speed without introducing external information (radar, GPS, wheels rotation, airspeed, magnetic and gravitational field change, Doppler shift in radio waves, etc). This is the relativity principle in action, which says that all the inertial frames of reference are equivalent.

by nuccy 5y ago

dtgriscom 5y ago

> they will inevitably accumulate uncertainty for long eventless movements Actually, they constantly accumulate uncertainty; no change in motion required.

nuccy 5y ago
True, but what you describe is related to the measurement and sampling accuracy. Until such sensors hit the Heisenberg uncertainty levels of precision on the readout/sensing, such uncertainties may be decreased further, there is no physical constrain on that (more sensors may help with that also). While it is in principle physically impossible to even identify the fact of movement linearly with constant speed without introducing external information (radar, GPS, wheels rotation, airspeed, magnetic and gravitational field change, Doppler shift in radio waves, etc). This is the relativity principle in action, which says that all the inertial frames of reference are equivalent.