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Receiver (DBR) that connects to the GPS receiver. The advent of WAAS has largely negated the
need for the added expense of a DBR in the United States.
Distance To Go: Distance To Go is the straight-line distance between Present Position and the
Destination Waypoint. DTG and SOG (Speed Over Ground) are used to calculate Time To Go. See
Time to Go and Speed Over Ground.
Estimated Position Error (EPE): Estimated Position Error is a calculation that indicates the potential
position inaccuracy the user may experience due to a variety of GPS factors which include satellite
position in the sky, signal strength and others factors.
Fix Type: Fix Type indicates whether the GPS receiver is providing 2D fix or 3D fix. A 2D fix requires
only three satellites and provides only latitude and longitude. A 3D fix requires four or more
satellites, and provides latitude, longitude and altitude.
GPS: GPS is an acronym for Global Positioning System. GPS provides accurate position (latitude,
longitude, altitude) information virtually anywhere on the earth through satellite technology and
personal receivers on the ground. A series of geosynchronous satellites broadcast a unique signal
toward the earth once per second. A GPS receiver, such as that included with many Humminbird®
products, receives the signals from these satellites and is able to determine position based on very
slight differences in the time each signal is received and the receiver’s knowledge of the location
of each of the satellites.
Heading: Heading describes the direction the boat is pointing and is measured in degrees (i.e.
321°, where 000° is North, 090° East, 180° is South, 270° is West). Due to wind and waves, the
boat is often traveling in a slightly different direction than it is heading, and therefore Heading is
often confused with Course Over Ground. See Course Over Ground.
Map Datum: A Map Datum refers to a particular survey of the earth’s surface that was referenced
when creating a chart (i.e. WGS84). Since the earth is not flat, and not even consistently round, a
mathematical model must be used to translate coordinates from the sphere of the earth to the
flat surface of a chart. This mathematical model is the Map Datum. Historically, many different
Map Datums have been used around the world to create maps; often a reference to the Map
Datum can be found in the legend of a paper map. It is important to select the correct Map Datum
setting in your fishfinder when comparing GPS position to a paper chart to avoid slight position
inaccuracies. Almost all electronic charts use the WGS84 Map Datum and therefore, they do not
require setting changes.
MMC: MMC is an acronym for Multi Media Card. An MMC is a postage stamp-sized memory
device used to store electronic data such a maps, waypoints, routes and other information. 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.