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Navigational Calculations
To call up the Navigation window, select the menu item File / Navigate.
Enter the latitude and longitude of your starting and destination locations. The course and distance are calculated automatically as you do this, if the latitudes and longitudes are valid. You can enter these values either as degrees, or as degrees and minutes, or as degrees, minutes and seconds. Click on one of the top line of radio buttons in the 'Units' box to change the format in which these are displayed.
The second line of radio buttons allows you to select the unit used for
distance. This is normally nautical miles.
The 'Reverse' button swaps over the start and destination
positions, and recalculates the course. Bearings are shown to the nearest tenth
of a degree. Greater precision than this is not useful, as there are so many
factors that can send you off course, and therefore any course should always be
recalculated on a regular basis.
Courses are calculated for a Great Circle and for a Rhumb Line. A Great Circle can be imagined by stretching a piece of thin string over a globe between two points. The shortest route between two points is a section of a Great Circle. A Rhumb Line is the course plotted as a straight line on a map made with a Mercator projection. It is a course where the bearing remains constant, crossing every meridian at the same angle. With a Great Circle, the bearing constantly changes.
As an example of this, if you click on the 'Reverse' button when the original values are showing, you will see the courses calculated for travelling in the reverse direction. The rhumb line bearings always differ by 180 degrees, but the initial Great Circle course is far less predictable.
The log file button at the bottom centre of the window will record the current calculation to the log file.
Example
When the window first opens, as shown in the image above, it shows the course from JFK Airport, New York, to Heathrow Airport, London. The great circle route is appreciably shorter than the rhumb line for this course.
Caution
The navigational calculations are intended for purely educational and illustrative purposes, and are not intended to be used for real world navigation.