FA-68969 / Tide and marine navigation tables / Member archive

Bridge air draft clearance: Rising tide increases the bridge clearance · case 04

Clearance appears to grow as the tide rises, approving transits at high water.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Input [c, mhws, tide, air, safety]: charted vertical clearance c is measured above MHWS; mhws and tide are heights above chart datum; air is the vessel air draft. Available clearance = c+(mhws-tide) (it shrinks when the tide exceeds MHWS). Return [round(avail,2), round(avail-air,2), avail-air>=safety].

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
bridge air draft clearance [12.5, 6.1, 0.4, 17.0, 0.5]	`[6.8, -10.2, false]`	`[18.2, 1.2, true]`	Failed

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