Which navigation method relies on speed, heading, and time to estimate a vessel's position?

Which navigation method relies on speed, heading, and time to estimate a vessel's position?

• A. Celestial navigation
• B. Dead reckoning
• C. GPS-based navigation
• D. Loran-C navigation

Answer: (B)

Dead reckoning estimates where the vessel is by projecting from a known position using its speed and heading over elapsed time. Start from a fixed point, multiply the speed by the time since the last fix to get distance traveled, and lay that distance along the path defined by the current heading on the chart. Repeating this each moment builds the estimated position as you move. This method is fundamental when you don’t have a fresh position fix in hand, and it’s especially used when GPS or other external navigation signals aren’t available. The catch is that small errors in speed, heading, or the influence of currents accumulate over time, causing the estimate to drift away from the true position unless you periodically reset it with an accurate fix from celestial observations, GPS, or another system. Celestial navigation and radio-based systems like Loran-C provide position fixes from measurements, not solely from projecting ahead with speed and time, while GPS gives direct position fixes rather than a forward projection.