Departure Distance Calculation

Wg Cdr Rajagopal

Departure

Index

Departure Distance between two Meridians

  • Departure is the distance between two meridians at a given parallel of latitude
  • One minute of latitude would be one nautical mile along the equator and all meridians
  • The rule does not apply to distances between meridians at other latitudes
  • Distance between meridians is maximum at equator and reduces to zero at the poles
  • Departure follows a cosine curve of latitude
  • Parallels of latitude are rhumb lines hence it is a rhumb line distance
  • Rhumb lines do not represent the shortest distance between two points
  • Departure is measured either in nautical miles or in kilometres

Calculation of Departure

  • The formula for departure in nautical miles is given by an equation
  • Departure = Change in minutes of longitude x cosine latitude
  • Departure is inversely proportional to latitude or increase in latitude decreases departure value

Best of luck