Dead reckoning — DR plot maintenance

Bowditch Ch. 1 §101

Bowditch Ch. 1 §101 — Introduction to Marine Navigation Marine navigation is the art and science of determining a vessel's position and conducting it safely from one point to another. Its four primary methods are dead reckoning, piloting, celestial, and electronic — modern voyages combine all four with electronic navigation as the principal real-time reference and the others as cross-checks.

Bowditch Ch. 1 §102

Bowditch Ch. 1 §102 — Introduction to Marine Navigation Dead reckoning (DR) is the determination of position by applying course steered and distance run from a known starting point. DR accuracy degrades over time and must be confirmed by external fixes whenever possible.

Bowditch Ch. 1 §103

Bowditch Ch. 1 §103 — Introduction to Marine Navigation Piloting is navigation by reference to landmarks, aids to navigation, and soundings. It is the primary method used in confined waters where dead reckoning alone is insufficient and electronic positioning may be obstructed by terrain or interference.

Bowditch Ch. 23 §2301

Bowditch Ch. 23 §2301 — Navigational Errors Navigational errors arise from instrument error, observation error, plotting error, computation error, and the basic assumption that the vessel has held the planned course. Cumulative errors must be checked against fixes whenever possible.

Bowditch Ch. 23 §2302

Bowditch Ch. 23 §2302 — Navigational Errors Set and drift describe the effect of current on the vessel's track. Set is the direction toward which the current is flowing; drift is the speed of the current. The vector sum of the intended course (course made good through water) and the current vector gives the actual course over ground.

Bowditch Ch. 24 §2402

Bowditch Ch. 24 §2402 — Currents The vector triangle for current correction is: course steered + drift vector = course made good. Inverting it: from course made good and drift, derive the course steered required to make a given track over ground.