Humminbird 786CI User Manual download pdf (Page 10)

How GPS and Cartography Work

Your 700 Series™ Chartplotter supports GPS and chartplotting. It uses GPS

to determine your position and display it on a grid. The Global Positioning

System (GPS) is a satellite navigation system designed and maintained by the

U.S. Department of Defense. GPS was originally intended for military use;

however, civilians may also take advantage of its highly accurate position

capabilities, typically within +/- 4.5 meters, depending on conditions. This

means that 95% of the time, the GPS receiver will read a location within 4.5

meters of your actual position. Your GPS Receiver also uses information from

WAAS (the Wide Area Augmentation System), EGNOS (the European

Geostationary Navigation Overlay Service), and MSAS (the MTSAT Satellite

Augmentation System) satellites if they are available in your area.

GPS uses a constellation of over 24 satellites that

continually send radio signals to the earth. Your

present position is determined by receiving signals

from up to 16 satellites and measuring the

distance from the satellites.

All satellites broadcast a uniquely coded signal

once per second at exactly the same time. The GPS

receiver on your boat receives signals from

satellites that are visible to it. Based on time

differences between each received signal, the GPS receiver determines its

distance to each satellite. With distances known, the GPS receiver mathematically

triangulates its own position. With once per second updates, the GPS receiver

then calculates its velocity and bearing.

How GPS and Cartography Work

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Humminbird 786CI User Manual Page 10