I remember working on the "Carousel IV" in the 70s, for commercial aviation. The accelerometers were mounted on a rotating platform, a carousel, to improve the accuracy. By rotating, the errors in the acceleration signal would somewhat cancel out. The device was a bit larger than the micromachined accelerometer chips in your cell phone.
The developers were quite proud that the device allowed an airplane to fly from Europe to LA, and only miss the airport by a mile, or so.
That is pretty darn good!
As good as most celestial navigation on ships.