Description
Add convergence to gridAzimuth and wrap the sum modulo 360 for trueAzimuth; separately normalize gridAzimuth modulo 360.
Map-grid directions and lengths depend on a projection and its local distortion. A supplied convergence or scale term can transform one local quantity, but does not define or execute the entire map projection.
Add convergence to gridAzimuth and wrap the sum modulo 360 for trueAzimuth; separately normalize gridAzimuth modulo 360.
When to use this tool
Use Geographic Azimuth Meridian Reference Pair when you need one projection-related local term under an explicit convention.
How to use the tool and how it works
- Enter gridAzimuth, convergence. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read trueAzimuth, gridAzimuth. Use the output convention below.
Add convergence to gridAzimuth and wrap the sum modulo 360 for trueAzimuth; separately normalize gridAzimuth modulo 360.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| gridAzimuth | Grid Azimuth | Required. Finite number. |
| convergence | Convergence | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| trueAzimuth | True Azimuth | Required. Finite number. |
| gridAzimuth | Grid Azimuth | Required. Finite number. |
{
"input": {
"gridAzimuth": 350,
"convergence": 15
},
"output": {
"trueAzimuth": 5,
"gridAzimuth": 350
}
}Limitations and assumptions
- Angles use degrees and the supplied convention is true azimuth equals grid azimuth plus convergence. No convergence, projection, magnetic declination, or coordinate reference is derived.
- 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 a complete coordinate-reference transformation with known parameters for mapping. Derive local convergence and scale from the chosen projection rather than assuming they apply uniformly.
References
Similar or alternative tools
- Meridian Convergence Local Input Term
Return arctangent of tan(longitude difference) times sin(latitude).
- East North Up Vector Azimuth Component
Return atan2(east, north) in degrees wrapped into [0, 360), and hypot(east, north) for horizontalMagnitude.