Addressing Errors in Dead Reckoning Calculations — How To Fix?

Identifying and Correcting Errors

When errors in dead reckoning calculations are discovered, it’s essential to determine the root cause. This can be done by cross-checking data from various navigation methods, such as celestial navigation or GPS, to verify the vessel’s actual position and speed. For example, if the dead reckoning calculation shows a position 5 miles off from the GPS reading, it’s likely that the error is due to an incorrect speed or heading input.

Recalculating the Position

Once the root cause of the error is identified, the position can be recalculated using the verified data. This involves applying the correct speed, heading, and time interval to the previous position to determine the new position. To increase accuracy, it’s recommended to use a 10-15% margin of error when adjusting the speed and heading inputs. For example, if the vessel’s speed is reported as 10 knots, a 10% margin of error would result in a speed of 11 knots being used for the recalculation.

Accounting for External Factors

External factors such as wind, currents, and waves can significantly impact the vessel’s speed and direction, leading to errors in dead reckoning calculations. To account for these factors, navigators can use various techniques, such as drift calculations or current tables, to estimate the vessel’s actual speed and direction. For example, if the wind is blowing at 20 knots, the navigator can apply a 2-3 knot reduction in the vessel’s speed to account for the wind resistance.