Voyage Planning • Static & Dynamic UKC • Squat • Tide • CATZOC / Depth Uncertainty • Speed Envelope • S-129 UKCM
Under Keel Clearance, Squat & Tidal Margin Tool
Screen a shallow-water transit from charted depth through tide, draft, squat, heel, wave response and survey uncertainty. The tool separates static UKC from dynamic UKC, compares the result with the vessel's company or port minimum, and estimates the speed, tide or draft change needed to recover margin.
Vessel & Passage Basis
Use the vessel's actual passage-plan draft and the port/pilot/company UKC policy. IMO voyage-planning guidance requires UKC, squat and heel effects to be considered, but does not impose one universal minimum UKC percentage.
m. Used for context and route reporting.
m. Used for heel-immersion screening.
Used only by the optional Barrass screening estimate.
m, planning condition.
m, planning condition.
mm at summer displacement. Enter approved vessel value if density correction is needed.
t/m³. Density draft correction is optional below.
Critical Depth & Water Level
m relative to chart datum or controlling reference.
m above chart datum. Negative values allowed.
m. Positive raises water, negative reduces it.
m deducted conservatively from available depth.
Advanced Route-Leg Register
Enter each critical channel, bar, berth approach or turning basin separately. The route verdict is controlled by the lowest dynamic UKC margin; safe legs cannot average away a failed leg.
| Leg / location | Depth m | Tide m | Surge m | Speed kn | Current kn | Waterway | Manual squat m | Wave m | Heel ° | Survey allowance m | Min UKC m |
|---|
Squat & Speed
knots. Use speed through water, not SOG, for squat screening.
knots. Informational for SOG; squat remains tied to through-water speed.
m. Used only when manual method is selected.
For S = k × Cb × V² / 100. Screening only.
knots, used to show recoverable squat margin.
Dynamic Draft & Motion Allowances
degrees. Tool screens extra immersion at approximately half-beam.
m. If greater than zero, overrides geometric heel estimate.
m. Use vessel/port-approved response allowance where available.
m for steering, bank interaction, passing effects or other approved allowance.
Depth Quality / Survey Uncertainty
m. Use the approved company/port approach.
m, if separately required by procedure.
Company / Port UKC Policy
m. Enter vessel/port/company requirement.
% of governing static draft. Enter only if your procedure uses this basis.
m above the formal minimum for this screening case.
Passage Readiness & Commercial Context
tonnes/cm. Used only for illustrative draft/cargo opportunity.
USD/day.
hours.
USD/tonne, optional planning value.
Navigation limitation: This tool is a planning screen, not a navigational authorization. It does not replace the Master's judgement, approved voyage plan, pilot advice, port UKC policy, official ENC/chart and notices, hydrographic/tidal services, vessel-specific squat data, dynamic UKC service, loading computer, stability information or company SMS. Empirical squat and CATZOC calculations are intentionally labeled as screening estimates.