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Estimated Position Er ror (EPE) A calculation that i ndicates th e p otential p osition inaccuracy the usermay experience due to a variety of GPS factors which include satellite position in the sky, signal strength, and others factors.

Fix Type Indicates whether the GPS receiver is providing 2D fix or 3D fix. A 2Dfix requires only three satellitesand provides only latitude and longitude. A 3D fix requires four or more satellites, and provides latitude, longitude, and altitude.

GPS (Global Positioning System) GPS provides accurate position (latitude, longitude, altitude) information virtually a nywhere on th e earth through sa tellite technology and personal receivers on the ground. SeeHow GPS Works.

Heading 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 towind 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 Refers to a particular survey of the earth’s surface that was referenced when creating a chart (ie. . WGS84).It is important to select the corect Map Datum setting in your fishfinder when c omparing GPS posi tion to a pape r cha rt to a void slight positio n inaccuracies. Almost all electronic charts use the WGS84 Map Datum and therefore, they do not require setting changes.

MMC (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 avery rugged format suitable for the marine environment, but it is not waterproof. MMC is the same formatthat many digital cameras use. See SD.

North, Magnetic The pr inciple reference po int of the co mpass (i.e . Nor th is 0 00°). Magnetic North relies on the ea rth’s magnetic field to align a metal pointer generally towards True North. However, due to localvariations in the earth’s magneticfield around the globe, the difference between True Northand Magnetic North can be greater than10°. See True North.

North, True 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. See

Magnetic North.

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