Furuno GP-3500 Operator's Manual page 127

9. CUSTOMIZING YOUR UNIT
MAGNETIC VARIATION
The location of the magnetic north pole is different from the geographical north
pole. This causes a difference between the true and magnetic north location.
This difference is called magnetic variation, and varies with respect to the
observation point on earth. Your unit is preprogrammed with all the earth's
magnetic variation. However, you may wish to enter variation manually to refine
accuracy.
1. Rotate the [ENTER] knob to select MAGNETIC VARIATION.
2. Press the [2] key to select "2. MANUAL."
3. Key in the magnetic variation referring to a nautical chart.
4. Press the [CURSOR ON/OFF] key to switch from East to West and vice
versa.
5. Press the [ENTER] knob.
HEADING MARKER
You may extend a line from the own ship position to show ship's heading.
(Heading data is required.) The length of line depends on the setting of
COURSE VECTOR below.
COURSE VECTOR
The course display, which may be a vector or bar, may be turned on or off as
appropriate.
Vector: Length varies with speed. (The length is not affected by display scale.)
Bar: Shows course.
WAYPOINT SWITCHING
Chooses waypoint switching method, PERPENDICULAR or ARRIVAL CIRCLE.
(See page 7-10.)
RNG & BRG MODE
When you set a destination, the equipment displays the range, bearing and
course to that destination. Range and bearing are calculated by the Great Circle
or Rhumb Line method. Route total distance is also calculated. Cross-track error
is only calculated in the Great Circle method.
Rhumb line: This method calculates the range and bearing between two points
drawn on a nautical chart. Since the bearing is kept constant it is ideal for
short-range navigation.
Great circle: This course line is the shortest course between two points on the
surface of the earth, like stretching a piece of string between two points on earth.
Because frequent course changes are required it is most suitable for long-range
navigation.
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