Fish Finders Terms And Expressions

AIS - Automatic identification system. An anti-collision system where boats send out information about their position, course, speed and identity. With an AIS receiver can be other boats with AIS presented on a map or radar image on a multifunction display.

ARPA - Automatic Radar Plotting Aid. Radar-based anti-collision and målfølgingsfunksjon. ARPA system will follow the goals that are designated as long as it is within radar coverage. Information about the course and speed display. An alarm will go if some of the ARPA objects are on a collision course with the ship. A professional ARPA system can typically follow the 100 objects.

BlueChart - Garmin's Boat Chart. Available in editions BlueChart, Vision and Vision G2. BlueChart G2 Vision has 3 dimensional map and a feature called Auto Guideance, this is a feature that can automatically find a "safe" route between two places.

Broadband Radar - Lowrance's designation of a new radartekonologi for marine use real name FMCW (Frequency Modulated Continious Wave). There are two major differences from conventional radar. FMCW transmitter as the name says out a continuing signal where the frequency changes after a repeterable pattern (modulated), this frequency change is necessary to detect the reflected signal. Conventional radar works on the same principle as sonar, a pulse is sent out, and so must wait for the longest possible reflection before a new pulse can be sent. FMCW using a half leader element to generate the radar signal, while the conventional rows using a tubes called magne tron. The advantage of the new technology is that it gives much better resolution of short hold, and that the semiconductor element will last as long as the electronics, while magnetrones burned out and need to be at commersially use replaces after 18-24 months. Sent effect is also lower for FMCW so that it will involve less danger to be irradiated by the radar. A FMCW uses advanced digital signal processing to detect the reflected signals.

C-MAP - Map Provider. The following companies provide C-Map plotters: Simrad, Furuno, Navman, Northstar, Lorenz, Tech Marine, Cobra, Seiwa and Standard Horizon. C-Map is available in versions NT +, MAX and MAX Pro.

CANet - Garmin bus for sharing data between sonar and chartplotters. Replaced by Ethernet to newer multi-function displays.

Digital depth sounder - Sonar using digital signal processing (digital filters) to improve the sonar signals. Is better to separate the individual fish in the shoals and bottom and has less surface noise. Works better than conventional solder in automatic operation.

DSC - Digital Selective Calling. VHF that can call up the second DSC radios automatically on the digital channel 70 using the MMSI number. Can send distress (Distress) with the position of the boat when a GPS is connected.

Garmin Marine Network - Garmin's marine-based Ethernet network

Grey Line - Function that makes it possible to determine it is hard or soft bottom and makes it easier to separate the fish that are close to the bottom in from the bottom. All echoes stronger than the value set in the menu colored gray. A thick grey line means hard bottom.

EGNOS - European Geostationary Navigation Overlay Service. System to improve the accuracy of GPS. The system consists of ground stations to produce correction data, and satellites that send the data to the GPS receiver in the same frequency range used for GPS signals. When the system is complete provider should be positioning accuracy better than 2m 99% of the time. The system is not yet full developed, and it can sometimes be achieved better accuracy by disabling the EGNOS. WAAS is the American variant of EGNOS. A GPS that supports WAAS also supports EGNOS.

HD Sonar - High Definition sounder - Sonar using digital signal processing (digital filters) to improve the sonar signals. Is better to separate the individual fish in the shoals and bottom and has less surface noise. Works better than conventional solder in automatic operation.

Radar HD - High Definition Radar - Radar Receiver that uses digital signal processing to improve resolution and automatic operation.

IP - Standard for the party not gentle slow projection and water protection for the electronics boxes. The first digit stands for the dust density, the second for water protection. X in the first digit means it is not classified for the party not gentle slow projection. IPx7 means watertight, and it is recommended in open boats.

MARPA - Mini Automatic Radar Plotting Aid. Radar-based anti-collision and target following function. MARPA system will follow the goals that are designated as long as it is within radar coverage. Information about the course and speed display. An alarm will go if some of MARPA objects are on a collision course with the boat. A radar heading sensor with minimum 10Hz refresh rate is required to get the system to work, heading data can also be taken from some autopilots. A MARPA system can typically follow the 10-20 objects.

MFD - Multi-Function Display, on the Norwegian multi-function display. A screen that is a plotter when the GPS antenna and that can be developed using sonar and radar, and often also other features such as AIS and motor information. Used for devices with 6,5-7 "screens and larger.

MMSI - Maritime Mobile Service Identity. Nine-digit code used to identify DSC VHF radios

Motor Information - Some multi function screens can display engine data as fuel consumption, various engine temperatures, various pressure, tilt, and more. Connected to the engine either via NMEA 2000 or SmartCraft. Suzuki, Yamaha, Evinrude and Volvo Penta uses NMEA 2000, Mercury and Mercruiser using SmartCraft.

Navionics - Map Provider. The maps are in the Classic, Silver, Gold and Platinum editions. Raymarine, Lowrance, Eagle, Geonav, Humminbird, Furuno name 2, and the Northstar 6000i and 6100i use Navionics maps. Gold is the most current maps today. Platinum also have 3D function, various satellite images and much additional information about ports, etc.

NMEA - National Marine Electronics Association. Industry Organization for the marine electronics industry, a native American is now international. The most important for us users is that they define the standards for the exchange of information between the electronics in from various manufacturers. There is unfortunately no NMEA standard for Ethernet so it is not possible to share data over the Ethernet between the various manufacturers.

NMEA 183 - Standard for data transfer between marine instruments. The default data rate is 4800 baud. Separate lines to send and receive. A transmitter can operate three receivers. A receiver can only connect to a transmitter. If it takes several inputs to a NMEA multiplexer is used. The data transferred is identified by a 3-letter codes are called sentences.

NMEA 2000 - The new standard for linking marine instruments. Building on Can bus standard that is widely used in cars. It can connect up to 50 devices on the network with a total of 252 logical addresses. The network consists of 5 lines, 2 data + 2 power + screen. Sensors and other small devices can be powered from the 12V power bus, the main units must have separate supply. Maximum data rate is 250kbit / s. It is important to be aware that a NMEA 2000 network must be terminated with 120 ohm resistors at both ends, this is done with special end terminators. The messages sent over the NMEA 2000 PGN identified by a number. Detailed information about decoding PGN number is as of today is not freely available. SimNet (Simrad), SeaTalk 2 and NG (Raymarine) and LowranceNet are variations of NMEA 2000. SimNet and Setalk 2 and HS do not use the standard NMEA connectors but the transitions are available from Mare Tron. LowranceNet exists in two versions with red and blue connector. The red was introduced in 2007 and is the standard NMEA 2000 cabling, the blue is an older proprietary connector. Transitions is available from Lowrance. There is as of today (January 2008) no universal NMEA 183 to 2000 conversion, but the first is waiting for the market in the spring of 2008.

SeaTalk - Raymarine data bus for the pairing of instruments. The bus also provides 12V PSU and consists of 3 lines.

SeaTalk HS - Raymarine Ethernet-based networks (100Mbit) for transferring large amounts of data between devices in the E and G series and between these and the PC running GH LUCAS RNS.

SmartCraft - Protocol for digital instruments for later Mercury and Mercruiser engines. Supported by Navman and Northstar chartplotters and multifunction displays.

Rate Gyro - A sensor that measures the boat's rotation with high accuracy. Used to improve the course of data coming in from the compass. The rate gyro is better to detect rapid course changes. The sensor is typically implemented as a MEMS gyroscope. Rate Gyro is used to provide better training data to autopilots and radars.

Rate Compass - Combined rate gyro and compass

Virtual Feedback (VF) - Software-based algorithm of autopilot that allows the pilot does not need ruther sensor. Simplifies installation and improves reliability.

WAAS - Wide Area Augmentation System. The U.S. system to improve the accuracy of GPS positioning. The system consists of ground stations to produce correction data, and satellites that send the data to the GPS receiver in the same frequency range used for GPS signals. WAAS is motsening to the European EGNOS fully operational.