NorthStar Navigation NorthStar 491 manual Glossary

Glossary

A-scope A horizontally magnified view of each echo, where the strength is shown by the width as well as the color of the line.

COG Course-Over-Ground. The actual path of your vessel relative to the surface of the earth.

clutter Distracting echoes caused by turbulence, plankton, etc. Can be reduced by the clutter control.

current The horizontal movement of water caused by tidal or other forces.

default A choice made automatically by the echo sounder; some defaults can be overridden in partial automatic mode.

echo The sound returned by either an object below the water’s sur- face or by the seabed, when this object or seabed is detected by a sound wave.

echo sounder An instrument that uses sound waves to measure the depth of a body of water or an object (such as a school of fish) below the water’s surface.

fathom A depth measurement that equals six feet or 1.83 meters of water.

gain The amount of amplification given to the received echo before it is displayed.

GPS Global Positioning System. hue The gradations of a color.

interference The electromagnetic interruption of a radio signal that causes a poor signal reception. Interference may originate from exter- nal sources, such as another nearby echo sounder, or from the vessel itself, such as alternator noise.

latitude Imaginary lines on the earth's surface running East/West and expressed in degrees (0-90) north or south of the Equator. Used in conjunction with the North/South lines of longitude to determine position.

491 Echo Sounder Operations Manual Page 71