Description
Add sourceDatumElevation minus targetDatumElevation to heightAboveSource to obtain heightAboveTarget.
A vertical datum supplies the zero level from which a height or depth is measured. Changing that zero shifts the reported number without moving the physical surface.
Add sourceDatumElevation minus targetDatumElevation to heightAboveSource to obtain heightAboveTarget.
When to use this tool
Use Tide Height Datum Offset when you need a height conversion with a known datum offset.
How to use the tool and how it works
- Enter heightAboveSource, sourceDatumElevation, targetDatumElevation. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read heightAboveTarget. Use the output convention below.
Add sourceDatumElevation minus targetDatumElevation to heightAboveSource to obtain heightAboveTarget.1
A datum is a reference elevation. Tidal datum relationships are local, so a supplied offset should not be extended to a different area without suitable measurements.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| heightAboveSource | Height Above Source | Required. Finite number. |
| sourceDatumElevation | Source Datum Elevation | Required. Finite number. |
| targetDatumElevation | Target Datum Elevation | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| heightAboveTarget | Height Above Target | Required. Finite number. |
{
"input": {
"heightAboveSource": 3,
"sourceDatumElevation": 1,
"targetDatumElevation": 2
},
"output": {
"heightAboveTarget": 2
}
}Limitations and assumptions
- The datum elevations must be expressed on a common underlying reference; no station-specific offset is retrieved.
- 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
Obtain location-specific datum relationships and uncertainty from the responsible survey or hydrographic authority.
References
-
Calculation and input contract: nautical/tide-height-datum-offset — tool.io
-
Tidal Datums — NOAA Center for Operational Oceanographic Products and Services
Similar or alternative tools
- Tide Observation Reference Level Shift
Add oldDatumElevation minus newDatumElevation to height.
- Sounding Datum Uncertainty Sign
Subtract tideAboveDatum from measuredDepth for datumDepth.