3 ms·

True but drift is inherent in dead reckoning due to cumulative errors and evidently the trick this guy used eliminates the drifting or limits it (the prototype

True but drift is inherent in dead reckoning due to cumulative errors and evidently the trick this guy used eliminates the drifting or limits it (the prototype was accurate to 5 meters).

DamnInteresting 9y ago
Well, Wikipedia defines dead reckoning as: > the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time and course. It still seems applicable, even if the hardware has advanced sufficiently that errors are minimized.
- fisherjeff 9y ago
  Dead reckoning is exactly as described in that pull quote, but the problem is that when you integrate, e.g., accelerometer readings to get velocity, you also integrate its bias, which varies over time, and in the case of MEMS sensors will cause very significant errors. The solution described in this article significantly improves on that by using the pressure data on foot strike as an observation to estimate the IMU's biases and correct the IMU-only position and attitude. EDITED TO ADD: In many inertial navigation systems - presumably including this one - dead reckoning will still be used as a fallback in the case where corrections fail (i.e., no GPS or insufficient pressure data)
mikeash 9y ago
I think the position error will still be unbounded over time with this approach. What it does give you is sharply bounded velocity error, which in turn makes position error grow much more slowly. It’s basically dead reckoning as you’d see in a car (where you always know your speed pretty accurately) versus in a plane (where speed is an output of the dead reckoning process as well as an input).
jtuente 9y ago
The cumulative errors that this device reduces are inherent to the measurement, drift in dead reckoning is just the sum of the errors in measurement and the assumptions thereof. This device simply provides a more accurate dead reckoning with cheap IMU sensors.

True but drift is inherent in dead reckoning due to cumulative errors and evidently the trick this guy used eliminates the drifting or limits it (the prototype was accurate to 5 meters).

DamnInteresting 9y ago

Well, Wikipedia defines dead reckoning as: > the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time and course. It still seems applicable, even if the hardware has advanced sufficiently that errors are minimized.

fisherjeff 9y ago
Dead reckoning is exactly as described in that pull quote, but the problem is that when you integrate, e.g., accelerometer readings to get velocity, you also integrate its bias, which varies over time, and in the case of MEMS sensors will cause very significant errors. The solution described in this article significantly improves on that by using the pressure data on foot strike as an observation to estimate the IMU's biases and correct the IMU-only position and attitude. EDITED TO ADD: In many inertial navigation systems - presumably including this one - dead reckoning will still be used as a fallback in the case where corrections fail (i.e., no GPS or insufficient pressure data)

mikeash 9y ago

I think the position error will still be unbounded over time with this approach. What it does give you is sharply bounded velocity error, which in turn makes position error grow much more slowly. It’s basically dead reckoning as you’d see in a car (where you always know your speed pretty accurately) versus in a plane (where speed is an output of the dead reckoning process as well as an input).

jtuente 9y ago

The cumulative errors that this device reduces are inherent to the measurement, drift in dead reckoning is just the sum of the errors in measurement and the assumptions thereof. This device simply provides a more accurate dead reckoning with cheap IMU sensors.