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Trakgps - GPS Glossaire Technique Catégorie: Électrotechnique et Électronique Date & Pays: 06/11/2014, Fr Mots: 128

Altimètre
Un instrument pour déterminer l'altitude, particulièrement un baromètre anéroïde utilisé dans l'aviation qui détecte les changements de pression accompagnant les changements d'altitude.

Antenne Active
Une antenne qui amplifie le signal GPS avant de l'envoyer au récepteur.

Anti-Spoofing
Le chiffrage du code pour protéger les signaux d'être brouillés par des transmissions fausses de signaux GPS par un adversaire.

Balise
Émetteur stationnaire qui émet des signaux dans toutes les directions (également appelées une balise non directionelle). En mode DGPS, l'émetteur de balise envoit également des données de correction aux récepteurs GPS voisins pour une plus grande exactitude.

Bearing
La direction d'une boussole d'un endroit vers un autre, mesurée au degré le plus proche (également nommé azimut). Dans un récepteur GPS, le Bearing est habituellement la direction vers le but.

Cartes de base
Quelques unités GPS viennent avec des cartes de base intégrés, qui incluent typiquement les océans, fleuves, lacs, principales villes, plus petites villes, villes, autoroutes secondaires, routes, chemins locaaux, chemins de fer, aéroports, frontières politiques. Les cartes de base sont disponible dans une variété de secteurs de couverture, selon les besoins de l'utilisateur.

Cartographie
L'art ou la technique de faire des cartes ou des diagrammes. Les récepteurs GPS ont des cartes détaillées pour l'auto-guidage ou des cartes plutôt visuelles mais sans capacités d'indiquer la direction à suivre.

CDI
See Course Deviation Indicator.

Clock Bias
The difference between the indicated clock time in the GPS receiver and true universal time (or GPS satellite time).

Clock Offset
A constant difference in the time reading between two clocks, normally used to indicate a difference between two time zones.

CMG
See Course Made Good.

Coarse/Acquisition Code
(C/A Code) The standard positioning signal the GPS satellite transmits to the civilian user. It contains the information the GPS receiver uses to fix its position and time, and is accurate to 100 meters or better.

Code C/A
Voir Code Brut/Acquisition.

Code Division Multiple Access
(CDMA) A method whereby many radios use the same frequency, but each one has a unique code. GPS uses CDMA techniques with codes for their unique cross-correlation properties.

COG
See Course Over Ground.

Cold Start
The power-on sequence where the GPS receiver downloads almanac data before establishing a position fix.

Control Segment
A worldwide chain of monitoring and control stations that control and manage the GPS satellite constellation.

Coordinated Universal Time
(UTC) Replaced Greenwich Mean Time (GMT) as the world standard for time in 1986. UTC uses atomic clock measurements to add or omit leap seconds each year to compensate for changes in the rotation of the earth.

Coordinates
A set of numbers that describes your location on or above the earth. Coordinates are typically based on latitude/longitude lines of reference or a global/regional grid projection (e.g., UTM, MGRS, Maidenhead).

Course
The direction from the beginning landmark of a course to its destination (measured in degrees, radians, or mils), or the direction from a route waypoint to the next waypoint in the route segment.

Course Deviation Indicator
(CDI) A technique for displaying the amount and direction of crosstrack error (XTE).

Course Made Good
(CMG) The bearing from the 'active from' position (your starting point) to your present position.

Course Over Ground
(COG) Your direction of movement relative to a ground position.

Course To Steer
The heading you need to maintain in order to reach a destination.

Crosstrack Error
(XTE/XTK) The distance you are off the desired course in either direction.



Datum
A math model which depicts a part of the surface of the earth. Latitude and longitude lines on a paper map are referenced to a specific map datum. The map datum selected on a GPS receiver needs to match the datum listed on the corresponding paper map in order for position readings to match.

Differential GPS
(DGPS) An extension of the GPS system that uses land-based radio beacons to transmit position corrections to GPS receivers. DGPS reduces the effect of selective availability, propagation delay, etc. and can improve position accuracy to better than 10 meters.

Dilution Of Precision
(DOP) A measure of the GPS receiver/satellite geometry. A low DOP value indicates better relative geometry and higher corresponding accuracy. The DOP indicators are GDOP (geometric DOP), PDOP (position DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and TDOP (time clock offset).

Distance
The length (in feet, meters, miles, etc.) between two waypoints or from your current position to a destination waypoint. This length can be measured in straight-line (rhumb line) or great-circle (over the earth) terms. GPS normally uses great circle calculations for distance and desired track.

DOD
The United States Department of Defense. The DOD manages and controls the Global Positioning System.

Données d'Almanach
L'information transmise par chaque satellite sur les orbites et l'état de santé de chaque satellite dans la constellation GPS. Les données d'almanach permettent au récepteur GPS d'acquérir rapidement des satellites peu de temps après la mise en fonction.

Downlink
A transmission path for the communication of signals and data from a communications satellite or other space vehicle to the earth.

Elevation
The distance above or below mean sea level.

Ellipsoid
A geometric surface, all of whose plane sections are either ellipses or circles.

Ephemeris Data
Current satellite position and timing information transmitted as part of the satellite data message. A set of ephemeris data is valid for several hours.

Estimated Position Error
(EPE) A measurement of horizontal position error in feet or meters based upon a variety of factors including DOP and satellite signal quality.

Estimated Time Enroute
(ETE) The time it will take to reach your destination (in hours/minutes or minutes/seconds) based upon your present position, speed, and course.

Estimated Time Of Arrival
(ETA) The estimated time you will arrive at a destination.

Fréquence de Porteuse
La fréquence du résultat non modulé d'un émetteur par radio. La fréquence d'une porteuse GPS L1 est de 1575.42 mégahertz.

Frequency
The number of repetitions per unit time of a complete waveform, as of a radio wave (see L1 and L2 frequencies in this glossary).

Geocaching
A high-tech version of hide-and-seek. Geocachers seek out hidden treasures utilizing GPS coordinates posted on the Internet by those hiding the cache.

Geodetic Datum
A math model representing the size and shape of the earth (or a portion of it).

Geographic Information System
(GIS) A computer system or software capable of assembling, storing, manipulating, and displaying geographically referenced information (i.e., data identified according to their location). In practical use, GIS often refers to the computer system, software, and the data collection equipment, personnel, and actual data.

Geosynchronous Orbit
A specific orbit around where a satellite rotates around the earth at the same rotational speed as the earth. A satellite rotating in geosynchronous orbit appears to remain stationary when viewed from a point on or near the equator. It is also referred to as a geostationary orbit.

Global Positioning System
(GPS) A global navigation system based on 24 or more satellites orbiting the earth at an altitude of 12,000 statue miles and providing very precise, worldwide positioning and navigation information 24 hours a day, in any weather. Also called the NAVSTAR system. For more information, see About GPS.

Glonass
The Global Orbiting Navigational Satellite System; the Russian counterpart to the United States’ GPS system.

GoTo
A route consisting of one leg, with your present position being the start of the route and a single defined waypoint as the destination.

Greenwich Mean Time
(GMT) The mean solar time for Greenwich, England, which is located on the Prime Meridian (zero longitude). Based on the rotation of the earth, GMT is used as the basis for calculating standard time throughout most of the world.

Grid
A pattern of regularly spaced horizontal and vertical lines forming square zones on a map used as a reference for establishing points. Grid examples are UTM, MGRS, and Maidenhead.

Heading
The direction in which a vehicle is moving. For air and sea operations, this may differ from actual Course Over Ground (COG) due to winds, currents, etc.

Horloge Atomique
Une horloge très précise qui fonctionne en utilisant des éléments de césium ou de rubidium. Une horloge de césium a une erreur d'une seconde par million d'années. Les satellites GPS contiennent plusieurs horloges de césium et de rubidium.

Initialization
The first time a GPS receiver orients itself to its current location and collects almanac data. After initialization has occurred, the receiver remembers its location and acquires a position more quickly because it knows which satellites to look for.

Input/Output
(I/O) The two-way transfer of GPS information with another device, such as a nav plotter, autopilot, or another GPS unit.

Invert Route
To display and navigate a route from end to beginning for purposes of returning to the route's starting point.

Ionosphere
A region of the earth's atmosphere where ionization caused by incoming solar radiation affects the transmission of GPS radio waves. It extends from a height of 50 kilometers (30 miles) to 400 kilometers (250 miles) above the surface.

Latitude
A position's distance north or south of the equator, measured by degrees from zero to 90. One minute of latitude equals one nautical mile.

Leg
(Route) A portion of a route consisting of a starting (from) waypoint and a destination (to) waypoint. A route that is comprised of waypoints A, B, C, and D would contain three legs. The route legs would be from A to B, from B to C, and from C to D.

Line Of Sight (LOS) Propagation
Of an electromagnetic wave, propagation in which the direct transmission path from the transmitter to the receiver is unobstructed. The need for LOS propagation is most critical at GPS frequencies.

Liquid Crystal Display
(LCD) A display circuit characterized by a liquid crystal element sandwiched between two glass panels. Characters are produced by applying an electric field to liquid crystal molecules and arranging them to act as light filters.

Lithium Battery
A soft, silvery, highly reactive metallic element that is used in batteries where weight and cold weather conditions are concerns.

Local Area Augmentation System
(LAAS) The implementation of ground-based DGPS to support aircraft landings in a local area (20-mile range).

Longitude
The distance east or west of the prime meridian (measured in degrees). The prime meridian runs from the north to south pole through Greenwich, England.

LORAN
Loran, which stands for LOng RAnge Navigation, is a grid of radio waves in many areas of the globe that allows accurate position plotting. Loran transmitting stations around the globe continually transmit 100 kHz radio signals. Special shipboard Loran receivers interpret these signals and provide readings that correspond to a grid overprinted on nautical charts. By comparing signals from two different stations, the mariner uses the grid to determine the position of the vessel.

Magnetic North
Represents the direction of the north magnetic pole from the observer's position. The direction a compass points.

Magnetic Variation
In navigation, at a given place and time, the horizontal angle (or difference) between true north and magnetic north. Magnetic variation is measured east or west of true north.

Map Display
A graphic representation of a geographic area and its features.

Mean Sea Level
The average level of the ocean's surface, as measured by the level halfway between mean high and low tide. Used as a standard in determining land elevation or sea depths.

Mode d'opération 2D
Une position GPS bidimensionnelle qui inclut seulement les coordonnées horizontales (aucune altitude GPS). Elle exige trois satellites visibles au minimum.

Mode d'opération 3D
Une position GPS tridimensionnelle qui inclut les coordonnées horizontales et l'élévation. Elle exige quatres satellites visibles au minimum.

Multiplexing Receiver
A GPS receiver that switches at a very rapid rate between satellites being tracked. Typically, multiplexing receivers require more time for satellite acquisition and are not as accurate as parallel channel receivers. Multiplexing receivers are also more prone to lose a satellite fix in dense woods than parallel channel GPS receivers.

Nautical Mile
A unit of length used in sea and air navigation, based on the length of one minute of arc of a great circle, especially an international and U.S. unit equal to 1,852 meters (about 6,076 feet).

Navigation
The act of determining the course or heading of movement. This movement could be for a plane, ship, automobile, person on foot, or any other similar means.

Navigation Message
The message transmitted by each GPS satellite containing system time, clock correction parameters, ionospheric delay model parameters, and the satellite’s ephemeris data and health. The information is used to process GPS signals to give the user time, position, and velocity. Also known as the data message.

NAVSTAR
The official U.S. Government name given to the GPS satellite system. NAVSTAR is an acronym for NAVigation Satellite Timing and Ranging.

NMEA
(National Marine Electronics Association) A U.S. standards committee that defines data message structure, contents, and protocols to allow the GPS receiver to communicate with other pieces of electronic equipment aboard ships.

NMEA Standard
A NMEA standard defines an electrical interface and data protocol for communications between marine instrumentation.

North Up Orientation
Fixes the GPS receiver’s map display so north is always fixed at the top of the screen.

Parallel Channel Receiver
A continuous tracking receiver using multiple receiver circuits to track more than one satellite simultaneously.

Pixel
A single display element on an LCD screen. The more pixels, the higher the resolution and definition.

Position
An exact, unique location based on a geographic coordinate system.

Position Fix
The GPS receiver's computed position coordinates.

Position Format
The way in which the GPS receiver's position will be displayed on the screen. Commonly displayed as latitude/longitude in degrees and minutes, with options for degrees, minutes and seconds, degrees only, or one of several grid formats.

Précision, Exactitude
La mesure de combien une estimation de position GPS est bien positionnée.

Prime Meridian
The zero meridian, used as a reference line from which longitude east and west is measured. It passes through Greenwich, England.

Pseudo-Random Code
The identifying signature signal transmitted by each GPS satellite and mirrored by the GPS receiver in order to separate and retrieve the signal from background noise.

Pseudorange
The measured distance between the GPS receiver and the GPS satellite using uncorrected time comparisons from satellite-transmitted code and the local receiver's reference code.

Quadrifilar Helix Antenna
A type of GPS antenna in which four spiraling elements form the receiving surface of the antenna. For GPS use, quadrifilar antennas are typically half-wavelength or quarter-wavelength size and encased in a plastic cylinder for durability.

Radio Technical Commission For Maritime Services (RTCM) Special Committee 104
A committee created for the purposes of establishing standards and guidance for interfacing between radio beacon-based data links and GPS receivers, and to provide standards for ground-based differential GPS stations.

RAIM
Receiver Autonomous Integrity Monitoring; A GPS receiver system that would allow the receiver to detect incorrect signals being transmitted by the satellites by comparing solutions with different sets of satellites.

Route
A group of waypoints entered into the GPS receiver in the sequence you desire to navigate them.

RS-232
A serial input/output standard that allows for compatibility between data communication equipment made by various manufacturers.

Search The Sky
A message shown when a GPS receiver is gathering satellite almanac data. This data tells the GPS receiver where to look for each GPS satellite.

Segment Actif
Le segment d'un itinéraire actuellement étant voyagé. Le segment est cette partie d'un itinéraire entre deux points quelconques dans l'itinéraire.

Selective Availability
(SA) The random error, which the government can intentionally add to GPS signals, so that their accuracy for civilian use is degraded. SA is not currently in use.

Serial Communication
The sequential transmission of the signal elements of a group representing a character or other entity of data. The characters are transmitted in a sequence over a single line, rather than simultaneously over two or more lines, as in parallel transmission. The sequential elements may be transmitted with or without interruption.

Signal Analogue
La caractéristique principal des signaux analogues est qu'ils sont continus. En revanche, les signaux numériques se composent de valeurs mesurées à intervalles indépendantes.

SONAR
A system using transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distance to the floor of a body of water.

Space Segment
The satellite portion of the complete GPS system.

Speed Over Ground
(SOG) The actual speed the GPS unit is moving over the ground. This may differ from airspeed or nautical speed due to such things as head winds or sea conditions. For example, a plane that is going 120 knots into a 10-knot head wind will have a SOG of 110 knots.

Spread Spectrum
The received GPS signal is wide bandwidth and low power. The L-band signal is modulated with a pseudo-random noise code to spread the signal energy over a much wider bandwidth than the signal information bandwidth. This provides the ability to receive all satellites unambiguously and to give some resistance to noise and multipath.