Description
Add chartedDepth and tideHeight, subtract draft and squat for clearance, then subtract reserve for margin.
A clearance margin compares available vertical space with occupied space and any explicit allowance. Depths, water levels, and structure elevations must share compatible datums.
Add chartedDepth and tideHeight, subtract draft and squat for clearance, then subtract reserve for margin.
When to use this tool
Use Underkeel Allowance Explicit Components when you need a transparent component of a vertical clearance calculation.
How to use the tool and how it works
- Enter chartedDepth, tideHeight, draft, squat, reserve. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read clearance, margin. Use the output convention below.
Add chartedDepth and tideHeight, subtract draft and squat for clearance, then subtract reserve for margin.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| chartedDepth | Charted Depth | Required. Finite number. |
| tideHeight | Tide Height | Required. Finite number. |
| draft | Draft | Required. Finite number; minimum 0. |
| squat | Squat | Required. Finite number; minimum 0. |
| reserve | Reserve | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| clearance | Clearance | Required. Finite number. |
| margin | Margin | Required. Finite number. |
{
"input": {
"chartedDepth": 10,
"tideHeight": 2,
"draft": 8,
"squat": 0.5,
"reserve": 1
},
"output": {
"clearance": 3.5,
"margin": 2.5
}
}Limitations and assumptions
- Use a compatible vertical datum and length unit. Squat and reserve are supplied, not predicted, and dynamic hazards are omitted.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use current surveys, water levels, vessel data, and approved operational margins for an actual passage decision.
References
Similar or alternative tools
- Nautical Sounding Keel Datum Shift
Add transducerBelowSurface to sounding for waterDepth, then subtract draft for underKeel.
- Vessel Airdraft Bridge Datum Gap
Subtract waterElevation from bridgeElevation for availableClearance, then subtract nonnegative airDraft for margin.