Why is initial alignment performed with the platform stationary?

• A. Stationary conditions provide fixed gravity vector and no platform motion, enabling accurate estimation of attitude and gyroscope biases.
• B. To warm up the sensors.
• C. To calibrate the engine.
• D. To avoid needing a GNSS fix.

Answer: (B)

Initial alignment relies on a stable, known reference: gravity. When the platform is stationary, the gravity vector is constant in the body frame, so the accelerometers can directly map this known direction to the sensor readings. This lets the system determine the platform’s attitude (which way it’s pointing) with high accuracy. It also provides a clean condition to estimate gyroscope biases, because there’s no rotation to confuse bias with real angular motion. If the platform were moving during alignment, dynamic accelerations and rotations would mix with gravity, making it hard to separate orientation from sensor drift and bias, and the estimate would be unreliable. Warming up sensors or other tasks are not what enables a precise alignment; the key is having a fixed gravity reference with no platform motion.