Description
Add each stage to its datum elevation, then return secondElevation minus firstElevation.
A level reading is measured relative to an origin or datum. Adding an offset can express the same supplied observation in another compatible coordinate, while changing the reference label alone does not transform a datum.
Add each stage to its datum elevation, then return secondElevation minus firstElevation.
When to use this tool
Use Gauge Stage Datum Difference when you need one signed level, datum, or reference comparison.
How to use the tool and how it works
- Enter firstStage, firstDatum, secondStage, secondDatum. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read firstElevation, secondElevation, difference. Use the output convention below.
Add each stage to its datum elevation, then return secondElevation minus firstElevation.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstStage | First Stage | Required. Finite number. |
| firstDatum | First Datum | Required. Finite number. |
| secondStage | Second Stage | Required. Finite number. |
| secondDatum | Second Datum | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| firstElevation | First Elevation | Required. Finite number. |
| secondElevation | Second Elevation | Required. Finite number. |
| difference | Difference | Required. Finite number. |
{
"input": {
"firstStage": 3,
"firstDatum": 100,
"secondStage": 5,
"secondDatum": 98
},
"output": {
"firstElevation": 103,
"secondElevation": 103,
"difference": 0
}
}Limitations and assumptions
- Both results must use the same vertical reference and unit; datum identity, survey accuracy, and actual water-level change are not verified.
- 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
Verify the survey references, measurement direction, and calibration before using levels in an operational decision.
References
Similar or alternative tools
- Gauge Zero Stage Datum Shift
Add oldZero to stage for waterElevation and subtract newZero for shiftedStage.
- Staff Gauge Overlap Reading Gap
Compare firstReading+firstZero with secondReading+secondZero.