Vessel Positioning System

Topics: Global Positioning System, NMEA 0183, Navigation Pages: 5 (987 words) Published: April 29, 2013
Vessel positioning System
D.J Gondalia, Nayan Khunti, Shwetal Pawar, Unnati Patel
Guided by Prof.Sandip Dawada, Capt. Gaurab Nandi
Department of Electronics and communication
Government Engineering College, Bharuch (Gujarat)-392 002

Abstract: This paper about vessel Positioning System. Using this application We can determined vessel location in sea with help of longitude and latitude as

Well as we can get our speed, UTC time, and many other parameter which helpful in sea related to vessel location.

VPS (Vessel Positioning System) is the System which works on the Basis of GPS (Global Position System). With help of GPS receiver we can determine the location of vessel anywhere in sea. VPS indicated its own position in sea with GPS modulo. Using the Vessel Positioning System (VPS, a process used to establish a position at any point on the sea) the following two values can be determined anywhere on Earth 1.Vessel’s exact location (longitude, latitude and height co-ordinates) accurate to within a range of 20m to approx. 2.The precise time (Universal Time Coordinated, UTC).

Speed and direction of travel (course) can be derived from these co-ordinates as well as the time. The coordinates and time values are determined by several satellites orbiting the Earth.

The National Marine Electronics Association (NMEA) developed a standard over 20 years ago that defines the interface between various pieces of marine electronic equipment and navigational computers, allowing them to talk together and share vital information. NMEA data is transmitted from an information source such as a GPS, depth sounder, or gyro compass etc. These data sending devices are called “Talkers”. Equipment receiving this information such as a chart-plotter, radar, PC or NMEA display is called a “Listener”.

1.1 Communication specification
The NMEA 0183 standard is a purely digital data transmission scheme, using ‘1’s and ‘0’s in a binary format, to communicate a digital representation of the required information (depth, speed etc.) to a connected device. The NMEA standard defines the electrical signaling, data protocol and sentence formats for a 4800 baud serial data bus. The data communication specification for NMEA version 1, 2 and 3 is essentially the same as RS232 with the settings: 4800 baud, 1 start bit, 1 stop bit and “No Parity”. NMEA 0183 Sentence Format

All NMEA 0183 data is sent in the form of text sentences, each beginning with a ‘$’ or ‘!’ symbol, and use commas to separate each part of the sentence. NMEA codes are plain ‘ASCII’ text, and have the following format: $yyXXX,……… *xx <0D><0A>

* The sentence always starts with a ‘$’ or ‘!’ symbol

* A 2-digit ‘yy’ code follows, giving the instrument type (e.g. for a GPS device this should be ‘GP’, and for a depth sounder this should be ‘SD’)

* A 3-digit ‘XXX’ code follows, giving the sentence data type (e.g. ‘GGA’ is a ‘Global Positioning System Fix Data’ sentence, and ‘DBT’ is a ‘Depth Below Transducer’ sentence)

* A comma follows, then the contents of the sentence data, which changes depending on the data type and the current values of what is being monitored.

* The final part is an optional two-digit checksum - optional, but all good equipment will include this to help safe-guard the data in the sentence. The checksum is preceded by the ‘*’ character and is calculated by taking the 8-bit exclusive-OR of all characters in the sentence, including ‘,’ delimiters, between but not including the ‘$’ / ’!’ and ‘*’ delimiters.

* The string always ends with a carriage return and line-feed combination (Hex 0D 0A, ASCII ‘\r\n’).

This is basic algorithm of decoding NMEA 0183 protocol data stream. And displaying position is as explained bellow. STEP 1: Establish communication link between GPS module and Laptop or Computer and start receiving...
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