Humminbird GR16 - Manual (Page 55)

ground stations around the coastal United States and on some inland waterways. These
correction signals are provided by the USCG and received by an auxiliary Differential Beacon
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.
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