Parallel-sailing conversion: difference of longitude (D.Long) from departure and latitude - applies when course is east-west.
Formula
$$ \Delta\lambda = p \sec \phi $$Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $p$ | Departure | nm | plane sailing |
| $\phi$ | Mean latitude | deg | chart |
Sources
- Bowditch Pub.9 Ch.24.