Which of the following best defines bias, scale factor, and misalignment errors in inertial sensors and their effects on navigation estimates?

• A. Bias is a constant offset; scale factor is a proportional error in gain; misalignment is axis misregistration.
• B. Bias is a random noise term; scale factor is a random drift; misalignment is not defined.
• C. Bias is a constant offset; scale factor is a proportional error in gain; misalignment is axis misregistration; All introduce systematic errors and cross-coupling in the navigation solution.
• D. Bias is a sensor noise; scale factor and misalignment do not affect navigation.

Answer: (C)

Understanding inertial sensor errors involves seeing how three common distortions enter the navigation solution as systematic, cross-coupling effects rather than random noise.

Bias is a constant offset in the sensor output. Even when the true quantity is zero, the reading sits at a fixed amount. In an inertial system, this steady bias on accelerometers or gyros leads to a continuous error signal that, once integrated, causes velocity and especially position to drift over time.

Scale factor is a proportional gain error. The sensor output is multiplied by a factor slightly different from the correct one, so the measured quantity is consistently too large or too small by a fixed fraction. Because the navigation solution relies on integrating these measurements, the proportional error accumulates with motion, producing growing inaccuracies in velocity and position.

Misalignment, or axis misregistration, means the sensor axes do not perfectly align with the navigation reference axes. The true vector components get projected into the wrong axes, creating cross-coupling between directions. Even small misalignments cause off-diagonal effects in the error terms, contaminating all axes of the solution.

All three errors are systematic and they introduce cross-coupling in the navigation estimates, which is why they’re described together as affecting the solution in a predictable, amplifying way over time.

The other options mischaracterize one or more of these error types or deny their impact on navigation, so they don’t capture the correct relationships as well as this description does.