NorthStar 951X Operator's Manual page 157

Calculating distance
and bearing
Setting distance and
speed units
951/952 Operator's Manual Rev. B
The unit can calculate the distance and bearing to your
intended destination along either a great circle route or a
rhumb line.
Regardless of the selection you make, cross-track error—including the
steering indicator and autopilot output—is always calculated from a
rhumb line.
The shortest distance between any two points on the surface
of a sphere is called a great circle route. It appears as a curved
line on a Mercator chart and is the unit's default method of
calculating distance and bearing to waypoints.
Rhumb line navigation maintains a constant true direction to
your destination (seen as a straight line on a Mercator chart),
but is a somewhat longer route to travel over great distances
than the great circle calculation. A rhumb line course might be
desired if a great circle route is likely to take you precipitously
close to bad weather or an unavoidable land mass.
Great circle and rhumb line are virtually identical if the start
and end points are closer than 100 nm.
To change this option, press the (',7 menu key, then use the
&85625 3$' to view the two choices. Press the (17(5 key
to make your selection, or &/($5 to leave the option
unchanged.
You can set the units of measurement for distances and speeds
to any of the following:
•
nautical miles and knots (nm/knots)
•
kilometers and kilometers per hour (km/kph)
•
statute miles and miles per hour (mi/mph)
This option also determines whether the STEERING screen's
cross-track and distance-to-waypoint information is displayed
in feet or meters.
To change this option, press (',7, then use the &85625 3$'
to view the available choices. Press the (17(5 key to make
your selection, or &/($5 to leave the option unchanged.
Chapter 11 - Customizing the Unit
NOTE:
Page 147