How do dead reckoning navigation and GNSS-based navigation differ, and what fallback methods exist if GNSS is degraded?

How do dead reckoning navigation and GNSS-based navigation differ, and what fallback methods exist if GNSS is degraded?

• A. Dead reckoning estimates position from course, speed, and time; GNSS provides precise position; fallback includes inertial navigation, celestial navigation, radar fixes; ensure continuous navigation capability.
• B. GNSS is unreliable and dead reckoning is always correct.
• C. Dead reckoning uses celestial navigation only.
• D. GNSS requires line-of-sight to satellites and has no fallback.

Answer: (A)

Dead reckoning and GNSS navigation differ in how they determine position. Dead reckoning starts from a known fix and projects your position forward using your course, speed, and elapsed time. It’s essentially an estimate built from motion data and can drift over time because small errors accumulate. GNSS, on the other hand, uses signals from satellites and precise timing to compute your geographic position directly, providing a much more precise fix without relying on prior movement data. If GNSS is degraded, you switch to fallback methods to maintain continuous navigation. An inertial navigation system uses onboard accelerometers and gyroscopes to track motion and calculate position and velocity, but it tends to drift over time without external updates. Celestial navigation uses measurements of stars or the sun to determine position independently of electronics. Radar fixes involve ranging or bearing to known landmarks or coastlines to determine location. Together, these options keep navigation going even when GNSS is unreliable.

Dead reckoning and GNSS navigation differ in how they determine position. Dead reckoning starts from a known fix and projects your position forward using your course, speed, and elapsed time. It’s essentially an estimate built from motion data and can drift over time because small errors accumulate. GNSS, on the other hand, uses signals from satellites and precise timing to compute your geographic position directly, providing a much more precise fix without relying on prior movement data.

If GNSS is degraded, you switch to fallback methods to maintain continuous navigation. An inertial navigation system uses onboard accelerometers and gyroscopes to track motion and calculate position and velocity, but it tends to drift over time without external updates. Celestial navigation uses measurements of stars or the sun to determine position independently of electronics. Radar fixes involve ranging or bearing to known landmarks or coastlines to determine location. Together, these options keep navigation going even when GNSS is unreliable.