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MMC is a very rugged format suitable for the marine environment, but it is not waterproof. The
MMC is removable from Humminbird® products, and can be used in a PC that is equipped with
an appropriate card reader. MMC is the same format that many digital cameras use. See SD.
North, Magnetic: North is the principle reference point of the compass (i.e. North is 000°).
Magnetic North relies on the earth’s magnetic field to align a metal pointer generally towards
True North. However, due to local variations in the earth’s magnetic field around the globe, the
difference between True North and Magnetic North can be greater than 10°. See True North.
North, True: North is the principle reference point of the compass (i.e. North is 000°). True
North uses the axis of the rotation of the earth as the reference for North and is constant for all
points on the earth. Most GPS units default to True North as the setting. The GPS heading may
vary from the boat compass heading because the compass uses Magnetic North. Humminbird®
GPS units provide the option of selecting True or Magnetic readouts by using the North
Reference menu. See Magnetic North.
Present Position: Present Position is the current location (latitude, longitude) determined by
GPS. The Present Position is indicated on-screen by a directional boat icon if the boat is moving,
or a round symbol if the boat is stationary.
Route: A Route is series of waypoints linked together in a specific sequence to define a
navigation path between two points, and saved in the fishfinder’s memory. Routes are often
used when frequently traveling between two or more locations because it is a faster and more
accurate method than repeatedly selecting individual waypoints each time one travels through
the same area. Routes consist of a Start Waypoint, an End Waypoint, and a series of waypoints
in between. Users can begin navigation at the beginning, the end (to run the route in reverse)
or at any waypoint in between. See Waypoint.
SD: SD is an acronym for Secure Digital. An SD card is virtually identical in function to an MMC;
however, the speed at which information can be accessed is generally faster, the storage
capacity is generally larger, and the card has security features which can be used to prevent
extracting the data from the card. SD is the same format that many digital cameras use. See
MMC.
Selective Availability: Selective Availability (SA) is a GPS system “feature” that can be
implemented by the U.S. Department of Defense (DoD) to degrade the accuracy of GPS
positioning information. With SA active, the GPS is accurate to within 100 meters 95% of the
time. With SA inactive, the GPS is accurate to within 45 meters 95% of the time. Currently, SA
is inactive and the consumer can enjoy the greater precision GPS provides; however, the DoD
reserves the right to activate SA at any time.
Speed Over Ground (SOG): Speed Over Ground is the measurement of the boat’s progress
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