Dead reckoning

Posted by ramel nortega

Dead reckoning

Further information: Dead reckoning

The navigator plots his 9am position, indicated by the triangle, and, using his course and speed, estimates his position at 9:30am and 10am.

Dead reckoning is the process of estimating present position by projecting course and speed from a known past position. It is also used to predict a future position by projecting course and speed from a known present position.The DR position is only an approximate position because it does not allow for the effect of leeway, current, helmsman error, compass error, or any other external influences.

The navigator uses dead reckoning in many ways, such as:

• to determine sunrise and sunset,
• to predict landfall, sighting lights and arrival times,
• to evaluate the accuracy of electronic positioning information,
• to predict which celestial bodies will be available for future observation.