Garmin GPSMAP 192C Owner's Manual

Also see for GPSMAP 192C: Quick reference guide Features

Contents

90 GPSMAP 192C Owner’s ManualU SING SONAR > U NDERSTANDING SONARUnderstanding SonarThe transducer mounted on your vessel transmits sound wavestoward the bottom of a lake, stream, or seabed in a cone-shapedpattern. When a transmitted sound wave strikes an underwaterobject—such as the bottom, a piece of structure, or a fish—soundis reflected back to the transducer. The transducer collects thereflected sound waves and sends the data to the GPSMAP 192C tobe processed and displayed. The underwater data is shown on theSonar display in the order that it is returned: first returned is thefirst on the display.Generally speaking, if the only thing between the transducer andthe bottom is water, the first strong return comes from the bottomdirectly below the transducer and sets the bottom level. Weakersecondary returns provide the detailed data. Stronger returnsdisplay in darker colors, with red being the strongest return.Understanding the Sonar DisplayOne of the first things to understand about sonar is that thetransducer sends a beam down to the bottom of the water, muchlike the beam of a flashlight. The beam starts small near yourvessel and expands as it gets to the bottom. Refer to “TransducerCoverage” for more detailed information.The Sonar page does not display a three-dimensional representationof the underwater environment; the display is in two-dimensions,much like if you took a picture of an aquarium. Only the depth ofthe item in the water is displayed. The Sonar display does not showyou where an item is located horizontally in the water, as shown inthe drawings below. The fish is not directly above the tree in reality,but it can look like they are on the Sonar page.20'10'1'Aerial View of the Water Sonar DisplayFishTreeTree