Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Distance from start

Required number input.

Bearing from start

Required number input.

Desired course

Required number input.

Calculate the signed perpendicular distance from a desired course given distance run and the bearing back to the start point. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Cross track error

The resulting cross track error returned as a number.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Ferry Glide Course

  Calculate the heading to steer so cross current lets the boat ferry glide onto the desired course, correcting by the arcsine of the current to boat speed ratio signed by the side the current comes from.

• Anderson Turn Course

  Calculate the return course reached by an Anderson turn, which rotates the heading two hundred forty degrees toward the chosen turn direction to bring the vessel back along its original track.

• Position Error Circle

  Estimate the radius of the position error circle from a compass steering error as distance run times the error in degrees divided by fifty seven point three.