Description
Subtract waterElevation from bridgeElevation for availableClearance, then subtract nonnegative airDraft 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.
Subtract waterElevation from bridgeElevation for availableClearance, then subtract nonnegative airDraft for margin.
When to use this tool
Use Vessel Airdraft Bridge Datum Gap when you need a transparent component of a vertical clearance calculation.
How to use the tool and how it works
- Enter bridgeElevation, waterElevation, airDraft. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read availableClearance, margin. Use the output convention below.
Subtract waterElevation from bridgeElevation for availableClearance, then subtract nonnegative airDraft for margin.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| bridgeElevation | Bridge Elevation | Required. Finite number. |
| waterElevation | Water Elevation | Required. Finite number. |
| airDraft | Air Draft | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| availableClearance | Available Clearance | Required. Finite number. |
| margin | Margin | Required. Finite number. |
{
"input": {
"bridgeElevation": 20,
"waterElevation": 3,
"airDraft": 15
},
"output": {
"availableClearance": 17,
"margin": 2
}
}Limitations and assumptions
- Elevations must share a datum and all lengths a unit; motion, survey uncertainty, and required reserves are not added.
- 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
- Underkeel Allowance Explicit Components
Add chartedDepth and tideHeight, subtract draft and squat for clearance, then subtract reserve for margin.
- Nautical Sounding Keel Datum Shift
Add transducerBelowSurface to sounding for waterDepth, then subtract draft for underKeel.