Which component of the GNSS/INS filter state is used to model slowly varying sensor biases?

• A. Gyroscope biases and accelerometer biases
• B. Clock biases
• C. Gravity
• D. Magnetic field

Answer: (A)

In an integrated GNSS/INS Kalman filter, slowly varying sensor biases are modeled by including bias states for the inertial sensors themselves—specifically the gyroscope biases and the accelerometer biases. These biases drift slowly over time due to temperature changes, aging, mounting effects, and other factors. By representing them as separate state variables with a slow-changing (often random-walk) dynamic, the filter can continuously estimate and compensate for this drift, keeping the integrated navigation from accumulating large errors.

Clock biases are a different part of the system, reflecting errors in the GNSS receiver or satellite clocks, not the inertial sensors. Gravity and the magnetic field are environmental/physical quantities used in dynamics or sensing models, but they’re not the slowly varying biases of the inertial sensors themselves.