Leica MX400 Operating Instructions Manual page 216

Glossary
Navigation based on Great Circle. The advantage of Great
Circle navigation is that it brings you the shortest way through
the active route. The disadvantage is that a Great Circle track
may differ from the straight rhumb line that is easily drawn on a
Mercator projected chart. Great Circle navigation is recom-
mended for ocean voyages only. The advantage increases by
higher latitude (north or south). It is biggest on an east/west
course and zero on a north/south course.
HDOP
An indicator of the two dimensional accuracy in position
(latitude and longitude). See DILUTION OF PRECISION.
HEADING
The direction in which the vessel is pointed, expressed as
angular distance from north clockwise through 360 degrees.
HEADING should not be confused with course. The HEAD-
ING is constantly changing as the vessel yaws back and forth
across the course due to the effects of sea, wind, and steering
error.
HEADING-TO-STEER
The angle of track required to steer the vessel or vehicle from its
present position to its planned destination point. This angle
differs from heading, which is its present angle of track with
respect to true north.
HEALTH
See SATELLITE HEALTH.
INCLINED PLANE
A geometric surface that is tilted with respect to another
arbitrary reference plane (for example, the earth's equatorial
plane).
INITIALIZE
To enter constants into the navigator to enable it to start posi-
tioning and/or navigating accurately.
INTERFACE
Electronic circuits that permit the passage of data between
different types of devices; for example, the speed and heading
interface circuit permits data from a speed log and compass to
Version 3.3
Operator's Manual
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