FA-68874 / Tide and marine navigation tables / Member archive

Harmonic tide prediction: Nodal factor is omitted from the amplitude · case 04

Predicted ranges are too small in years of strong lunar declination.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Input [t_minutes, z0, constituents]; each constituent is [H metres, g phase lag deg, speed deg/hour, nodal factor f, nodal phase u deg, equilibrium argument V0 deg]. Height above chart datum is z0 + sum f*H*cos(V0+u+speed*t_hours-g). Return rounded to 4 decimals.

Why this case matters

Tide tables and passage plans turn published predictions into go/no-go decisions about depth, clearance and timing.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
harmonic tide prediction [371, 2.1, [[1.2, 110.0, 28.9841042, 1.02, -2.1, 35.0], [0.4, 150.0, 30.0, 1.0, 0.0, 0.0], [0.25, 95.0, 15.0410686, 1.1, 8.5, 210.0]]]	`1.9728`	`1.9476`	Failed

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