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Wick St Lawrence, United Kingdom
Updated20/10/2017 07:50 

AIS Shipping Position Data

What is AIS?

AIS is initially intended to help ships avoid collisions, as well as assisting port authorities to better control sea traffic. AIS transponders on board vessels include a GPS (Global Positioning System) receiver, which collects position and movement details. It includes also a VHF transmitter, which transmits periodically this information on two VHF channels (frequencies 161.975 MHz and 162.025 MHz old VHF channels 87 & 88) and make this data available to the public domain. Other vessels or base stations are able to receive this information, process it using special software and display vessels locations on a chart plotter or on a computer.

What is the range AIS covers?

Normally, vessels with an AIS receiver connected to an external antenna placed on 15 meters above sea level, will receive AIS information within a range of 15-20 nautical miles. Base stations at a higher elevation, may extend the range up to 40-60 nm, even behind remote mountains, depending on elevation, antenna type, obstacles around antenna and weather conditions. The most important factor for better reception is the elevation of the base station antenna. The higher, the better. We have seen vessels 200 nm away, with a small portable antenna placed on an island mountain on 700 meters altitude! Our base stations cover fully a range of 40 miles and periodically receive information from some more distant vessels.