Net UKC = charted depth + tide − draft − squat − wave allowance − safety margin. The fundamental pilot-card number.
Formula
$$ \text{UKC} = H_\text{chart} + T_\text{tide} - T_\text{draft} - S_\text{squat} - W_\text{wave} - M $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $H_\text{chart}$ | Charted depth | m | nautical chart |
| $T_\text{tide}$ | Tide height | m | tide tables |
| $T_\text{draft}$ | Static draft | m | loading computer |
| $S_\text{squat}$ | Dynamic squat | m | Barrass / pilot |
| $W_\text{wave}$ | Wave allowance | m | sea state |
| $M$ | Safety margin | m | SMS |
| $UKC$ | Under-keel clearance | m | result |
Sources
- IMO MSC.1/Circ.1421 - UKC guidelines.
- PIANC WG121 - Harbour approach design.