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Marine Great Circle Navigation Calculator

This calculator requires the use of Javascript enabled and capable browsers. This script allows calculation of Great Circle navigation information, and the eventual desired waypoints for a long journey. For navigation purposes, the definition of a great circle is a circle on the surface of the Earth, the plane of which passes through the Earth's center. Without considering factors of weather, winds, magnetic deviation, currents and other possible effecting factors, the great circle track is the shortest distance between any two places on the surface of the Earth.

To sail a great circle track, the navigator needs to adjust the ship's course continuously because the great circle track is a curve when plotted on a Mercator Chart. It is unrealistic to attempt to sail on an exact great circle route. Realistically, to best make use of the shorter sailing distance of the great circle track, navigators usually divide a great circle track between the initial position and the destination into many much smaller segments (way points) of about one to two day's sailing time (obviously depending on the craft and conditions) and make course adjustments each day at the same time, usually at high noon. The total distance is therefore the sum of the distances of those segments calculated by means of Mercator Sailing. A potential problem of the great circle track, though is the shortest route between two locations, it also usually tracks closer to the pole (or to higher latitude) than either of the two places, origin or destination. High latitudes are often in peril because of bad weather and icing. A safe idea of a veteran sailor is to set a latitude limit for the long voyage plan. This policy is called composite great circle route planning, done with waypoints. This calculator relieves the tedious process of determining those waypoints for the voyage.

Enter the latitude and longitude information for origin and destination, paying attention to the hemisphere selection. Click on Calculate. The true course and various distances will be calculated. To get waypoint information, enter the limitations and click on Calculate Waypoints. To present a printable version of the entire waypoint calculation for the voyage, click on Calculate Full Track. Please also see our Meridional Parts Navigation Calculator and Detailed Meridional Parts Navigation Calculator.

Meridional Parts
Required Data Entry
Departure Position Co-Ordinates
Latitude Degrees Minutes
Longitude Degrees Minutes
Destination Position Co-Ordinates
Latitude Degrees Minutes
Longitude Degrees Minutes

Calculated Results
Initial Course Degrees True Rounded
Distance Nautical Miles Rounded
Distance Statute Miles Rounded
Distance Kilometers Rounded
Required Waypoint Entry
Way Point Longitude Degrees Minutes
Calculated Waypoint Results
Way Point Latitude Degrees Minutes N/S
Updated 8.15.11

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