GNSS Antenna Information

GNSS Antennas - Providing AIS With Position

marine electronics navigation F&C Marine

Author: George R Groves


Knowing your position whilst at sea is key to safe navigation. Over 20 years have passed since the first GPS receivers were commercially available and, in this time, the whole world has come to rely on this US funded technology. Now every boat, plane, car and train that we travel on has GPS navigation.  However Other countries are producing there own systems to rival the GPS.  All GNS devices also provide the ship with date and time data.


Global National Satellite System (GNSS).  This is the collective wording for all satellite systems. The leading system is Global Positioning System (GPS) which is american funded system. This has the best coverage across the whole world.  There closest rival is Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS).  Which is a Russian made satellite system.  This beats the GPS system at the very north and south of the earth due to the positioning of the satellites in space


GPS is an American system which will identify your position on earth.  GPS is an acronym which stands for Global Positioning System and is the leading satellite system in the world.  The U.S has achieved this feet by the positioning of their satellites in space and the amount of satellites they have.  The baseline satellite constellation of the GPS consists of 24 satellites positioned in six earth-centred orbital planes, with four operational satellites and a spare satellite slot in each orbital plane. The basic GPS signal is accurate on a worst-case basis to within approximately 100 meters lateral and 140 meters vertical everywhere on earth.  However if the GPS is accurate to the best-case scenario, then it is accurate to within 10 meters.


The GLONASS system has come along way from its early days. The first GLONASS satellite was launched on 12th October 1982 with the launch of Kosmos – 1413, Kosmos – 1414, Kosmos – 1415.  11 years later the system declared operational by the Russian Federation in 1993.  Come 1995 the system had reached its optimal performance with 24 satellites in space.  However with the collapse of the Russian economy the satellites fell into disrepair and the system was on the brink of failure but in the early 2000’s Valdmir Putin made restoring the GLONASS system a top government priority. In 2007 President Vladimir Putin signed a decree that the GLONASS system would provide a free service to all people. The system is now nearly as accurate as the GPS system.

AIS devices are capable of taking either GPS or GLONASS Satellite positioning.  Modern devices are capable of operating both systems simultaneously providing higher accuracy and better coverage.  Example of this is Em-Trak’s Class A AIS’s


Galileo  went live in 2016, created by the European Union (EU) through the European GNSS Agency (GSA), headquartered in Prague in the Czech Republic. The €10 billion project is named after the Italian astronomer Galileo Galilei. One of the aims of Galileo is to provide an independent high-precision positioning system so European nations do not have to rely on the U.S. GPS, or the Russian GLONASS systems, which could be disabled or degraded by their operators at any time. The use of basic (lower-precision) Galileo services will be free and open to everyone. The higher-precision capabilities will be available for paying commercial users. Galileo is intended to provide horizontal and vertical position measurements within 1-metre precision, and better positioning services at higher latitudes than other positioning systems. Galileo is also to provide a new global search and rescue(SAR) function as part of the MEOSAR system.

The first Galileo test satellite, the GIOVE-A, was launched 28 December 2005, while the first satellite to be part of the operational system was launched on 21 October 2011. As of July 2018, 26 of the planned 30 active satellites are in orbit. Galileo started offering Early Operational Capability (EOC) on 15 December 2016, providing initial services with a weak signal, and is expected to reach Full Operational Capability (FOC) in 2019. The complete 30-satellite Galileo system (24 operational and 6 active spares) is expected by 2020.


The BeiDou Navigation Satellite System (BDS) is a Chinese satellite navigation system. It consists of two separate satellite constellations. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and known as BeiDou-1, consists of three satellites which since 2000 has offered limited coverage and navigation services, mainly for users in China and neighbouring regions. Beidou-1 was decommissioned at the end of 2012. 

The second generation of the system, officially called the BeiDou Navigation Satellite System (BDS) and also known as COMPASS or BeiDou-2, became operational in China in December 2011 with a partial constellation of 10 satellites in orbit  

Since December 2012, it has been offering services to customers in the Asia-Pacific region. On December 27, 2018, Beidou-3 officially began to provide global services.  In 2015, China started the build-up of the third generation BeiDou system (BeiDou-3) in the global coverage constellation. The first BDS-3 satellite was launched on 30 March 2015. As of January 2018, nine BeiDou-3 satellites have been launched. BeiDou-3 will eventually consist of 35 satellites and is expected to provide global services upon completion in 2020. When fully completed, BeiDou will provide an alternative global navigation satellite system to the United States owned Global Positioning System (GPS), the Russian GLONASS or European Galileo systems and is expected to be more accurate than these. It was claimed in 2016 that BeiDou-3 will reach millimetre-level accuracy (with post-processing), which is ten times more accurate than the finest level of GPS.

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