Description
Subtract headingDegrees from bearingDegrees and normalize modulo 360.
Bearings are circular coordinates, so zero and 360 degrees represent the same direction. Sector boundaries and true, magnetic, compass, or relative references need explicit conventions.
Subtract headingDegrees from bearingDegrees and normalize modulo 360.
When to use this tool
Use Nautical: Bearing Relative To Vessel Heading when you need a bearing normalization, sign correction, or sector label.
How to use the tool and how it works
- Enter bearingDegrees, headingDegrees. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
Subtract headingDegrees from bearingDegrees and normalize modulo 360. Label zero ahead, 180 astern, the intervening clockwise half starboard, and the remaining half port.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| bearingDegrees | Bearing Degrees | Required. Finite number. |
| headingDegrees | Heading Degrees | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Result | Required. Object. |
| result.relativeBearingDegrees | Relative Bearing Degrees | Calculated result member: number. |
| result.side | Side | Calculated result member: string. |
{
"input": {
"bearingDegrees": 350,
"headingDegrees": 10
},
"output": {
"result": {
"relativeBearingDegrees": 340,
"side": "port"
}
}
}Limitations and assumptions
- Both inputs must use the same true or magnetic reference; no collision risk or maneuver is determined.
- Outputs are nested inside result. 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 heading and magnetic information and a complete navigation process when interpreting an actual course or contact.
References
Similar or alternative tools
- Relative Bearing Bow Quarter Label
Normalize relativeDegrees into [0, 360).
- Bearing Quadrant Token
For exact multiples of 90 return the caller's boundaryToken; otherwise select NE, SE, SW, or NW.