FA-68957 / Tide and marine navigation tables / Member archive

Under-keel clearance with squat: Safety margin is taken from the water depth · case 02

Deep berths demand an excessive clearance and refuse safe ships.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Input [charted, tide, draft, speed_kn, cb, confined, margin]. Charted value is depth below chart datum (negative means a drying height above datum). Squat = cb*speed^2/100 metres in open water and twice that when confined. UKC = charted+tide-draft-squat. Required clearance is margin*draft. Return [round(ukc,3), ukc>=required].

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
under-keel clearance with squat [11.0, 0.21, 10.0, 5, 0.8, false, 0.1]	`[1.01, false]`	`[1.01, true]`	Failed

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