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> simply integrating speed over time

This probably runs into issues with accumulated error, especially if the error in speed measurement has a serial correlation.




> probably runs into issues with accumulated error

Typically there's no single nor double integration required for a wheeled ground vehicle; distance (revolutions times wheel circumference) is the primary measurement, with speed being trivially computed from that plus an accurate clock.


That assumes there's insignificant slippage between the wheel and ground. A reasonable assumption for a rubber tire on a concrete road, with a 20 sq. in. contact patch. Less reasonable for steel on steel with a 2 sq. in. contact patch.


I certainly agree that there are still errors, wheel slip being a major one. However, that does not cause an accumulating/ever-compounding error in speed nor distance travelled in the way that, say, a one-time error from an IMU's accelerometer does.

The lack-of-integration common in wheeled ground vehicles is highly beneficial to long-term speed & distance accuracy; it's a main reason why odometers were accurate for literally thousands of years prior to anyone knowing how to build an equally-accurate aircraft/spacecraft IMU. (The Romans were able to achieve <0.5% errors over hundreds of miles by the first century AD, something that no aircraft IMU was consistently able to achieve until after WWII).


That’s what sensor fusion is for.

That said, inertial nav can take a plane across the country without correction and get within sight of the target.

I think integrating actual speed while on rails would be vastly more accurate.

And really, it just need to augment gps.


Sure, sensor fusion sounds reasonable. My mistake, I thought you were referring to GPS and speed integration as separate options.


Are you trying to reinvent already outdated ETCS level 2?


I'm not inventing anything.

And why would it be outdated if it works, and we (US) aren't using it.




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