The VN-200 also has a built-in microprocessor that runs a larger and more robust GPS/INS Kalman Filter at 200Hz.
The attitude accuracies are improved by the addition of the position and velocity measurements, and the “raw” GPS position and velocity measurements are improved by the accelerometer, gyro, and pressure sensor measurements.
When the VN-200 is in motion, the heading angle can be determined by comparing the position and velocity measurements to the accelerometers, such that the magnetometers can be ignored by the INS filter. The heading accuracy, relative to True North, is improved compared to an AHRS and magnetic disturbances no longer have an effect on the attitude solution.
- Note that the VN-200 can still use the magnetometers for providing a heading estimate upon start-up or when the GPS signal is lost).
Vertical position measurements from GPS modules typically have lower accuracies than the horizontal measurements. The barometric pressure sensor provides another measurement of vertical position to improve accuracy.
The INS filter also uses the GPS outputs to estimate the real-time accelerometer bias drift in addition to the gyro bias drift.