Glossary | GPS & Navigation Terms |
advent of WAAS has largely negated the need for the added expense of a DBR in the United States.
Distance To Go The
To Go. See Time to Go and Speed Over Ground.
Estimated Position Error (EPE) 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 Indicates whether the GPS receiver is providing 2D fix or 3D fix. A 2D fix requiresonly threesatellitesand 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 anywhere on the earth through satellite technologyand personal receivers on the ground. See How 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 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 Refers to a particular survey of the earth’s surface that was referenced when creating a chart (i.e. WGS84). It is important to select the correct Map Datum setting in your fishfinder when comparing GPS positionto 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 (Multi Media Card) An MMC is a postage
is a very rugged format suitable for the marine environment,but it is not waterproof. MMC is the same format that many digital cameras use. See SD.
North, Magnetic 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 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.
Present Position The current location (latitude, longitude) determined by GPS. The Present Position is indicated
Route A 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 (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.
147 | Glossary - GPS & Navigation Terms |