Check one idealized current-vector solution against an externally charted true heading, with explicit cross-track feasibility and no silent clamp.
Choose your path
Compare a feasible idealized current-vector heading with an externally charted true heading while exposing cross/along current and rejecting impossible cross-track solutions.
Use true directions, set-toward convention and STW consistently.
Enter the charted track, STW, current set/drift and independent charted heading.
Sees idealized heading/SOG and signed difference with transparent components.
Avoid a silently clamped pseudo-solution.
Enter the scenario and inspect the explicit infeasibility result when cross current exceeds STW.
Re-plans instead of steering an impossible heading.
Keep hazards, depth, traffic, leeway and changing conditions outside static arithmetic.
Verify every leg with current official ENCs/charts, Coast Pilot, notices, forecasts and competent navigation.
Never treats the worksheet as a heading order or route clearance.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
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The entered current set is the true direction toward which the water moves. Its vector is resolved into cross-track and along-track components relative to the intended true track.
A heading solution exists only when the magnitude of cross-track current does not exceed boat speed through water. Impossible cases are reported directly rather than forced through a clamped inverse sine.
The idealized heading and resulting SOG are compared with an externally charted true heading. The worksheet does not clear hazards, model leeway or replace current official navigation products.
Updated: August 2026
Enter intended track, STW and current set/drift to reproduce the idealized heading and SOG, then compare them with the independently planned heading.
Use the explicit infeasibility result to stop and re-plan when the cross-track current component exceeds entered STW.
Keep charted hazards, depth, traffic, true/magnetic conversion, leeway, current variation and weather in the official passage-planning workflow outside this arithmetic.
Marine current set is entered toward the direction the water moves. A from-direction reverses the vector.
All direction fields here are degrees true. Apply verified variation/deviation externally and keep the charted reference consistent.
This worksheet exposes one constant current-vector triangle, including cross-track feasibility, idealized heading, resulting SOG and difference from an externally charted heading. It is not a heading order, route clearance, autopilot command or substitute for competent navigation.