Garmin CS 1522, Owner'S Manual

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1.1 A Brief History of Sonars 5
CHAPTER 1 INTRODUCTION
WARNING
See the Important Safety and Product Information in the Installation Instructions for product
warnings and other important information.
You are responsible for the safe and prudent operation of your vessel. Sonar is a tool that
enhances your awareness of the water beneath your boat. It does not relieve you of the
responsibility of observing the water around your boat as you navigate.
All route and navigation lines displayed on the device are intended to provide general guidance to
identify proper channels, and are not intended to be strictly followed. Always refer to the navaids
and conditions on the water when navigating to avoid groundings or hazards that could result in
vessel damage, personal injury, or death.
1�1 A Brief History of Sonars
1�1�1 Basic Principles of Sonars
Sonar, originally an acronym for Sound Navigation and Ranging, is a technology that uses
sound propagation to detect objects under the surface of water. Sonar devices determine
the distance to objects by sending out sound pulses and measuring the time it takes for
the sound pulses to be reflected back.
1.1.2 Development of Sonars
Sonars were developed during the period of the First World War to assist in the detection
of submarines and icebergs under water. The technology received major improvements
during World War II, and eventually developed into modern fishfinders.
Fishfinders help detect schools of fish by transmitting ultrasonic waves from a transducer
mounted on the bottom of the boat, and listens for reflected echoes. The echoes over
time can then be plotted on a sonar display in relation to the depths of the water.
1.1.3 Determining the Distance
Fishfinders help detect schools of fish by transmitting ultrasonic waves from a transducer
mounted on the bottom of the boat. The pulse would reflect strongly off solid objects
like the seafloor, or more weakly off the air conserved in fish bladders. With the speed of
sound in water known (roughly 1,500 meters per second), the received echoes over time
can then be plotted on a sonar display in relation to the depths of the water.