Reconcile explicit Compass, Magnetic and True heading stages with signed deviation, signed variation and an independent true-heading reference.
A quick decision brief for this specific tool
Explicit compass heading C, heading-specific signed deviation, chart/location/date-specific signed variation and an independent true-heading reference
Calculated magnetic M and true T stages, total compass error and signed difference from the entered true reference
Corrects C→M→T by adding east and subtracting west, normalizes directions and preserves all reference labels; it does not adjust or certify a compass
Choose your path
Reconcile explicit Compass, Magnetic and True heading stages with current signed deviation/variation records and an independent true-heading reference.
Keep C, M and T labels and Add-East signs explicit.
Enter compass heading, heading-specific deviation, chart/date/location variation and independent true reference.
Sees magnetic/true stages and signed difference without label ambiguity.
Separate arithmetic from compass adjustment and local disturbance.
Verify compass identity, deviation table, variation source and independent reference externally.
Uses the worksheet as a record diagnostic rather than a compass certificate.
Keep current charts, notices, hazards and position checks above arithmetic.
Use official ENCs/charts and competent navigation for route and heading decisions.
Never treats the result as a heading order or autopilot command.
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 compass heading C is corrected by signed deviation to magnetic M, then signed variation converts M to true T. Every output retains its reference label.
East deviation and variation are positive; west values are negative. Directions are normalized after the two stages, including entered 360 degrees as 000.
The calculated true heading is compared with an independent entered true reference. The difference does not adjust, swing or certify a compass.
Updated: August 2026
Enter the exact compass reading, heading-specific deviation and current chart variation, then inspect the M and T stages.
Compare the arithmetic with an independent true reference before checking compass identity, deviation table, signs and local disturbance.
Use current official ENCs/charts, notices and competent navigation for steering, route clearance and position checks.
Compass C becomes magnetic M only after applying the current heading-specific deviation. Keep C, M and T labels distinct.
Variation is location/date specific; residual deviation depends on the vessel, compass and heading. Verify both sources and east/west signs.
Use this worksheet to reconcile one C→M→T heading record with an independent true reference. It is not a compass adjustment, navigation fix, heading order, route clearance or autopilot command.
