Setting Up SonarUse the Sonar tab on the Main Menu to set up the Sonar Page.To access the Sonar Tab:1. Press MENU twice to open the Main Menu.2. Use the ROCKER to highlight the Sonar tab.Main Menu—Sonar TabFish Symbols—select how the Sonar Page shows underwater targetsand background information. Select Off to show all of the availableinformation about the underwater environment. Select a fish symbol,to show only the information related to that symbol.Water Type—select the proper water type you are boating in.Because sound waves travel through fresh and salt water at differentrates, it is necessary to select the water type to ensure accuratereadings on the unit.Depth Number—select how efficient the digital depth update rateis. Fast Update updates quicker and is recommended for low-noisewater deeper than 50 feet. Auto is best for shallow water or high-noise areas, has a slower screen update, and is best used if you travela wide variety of depths.If the unit is unable to track the bottom for any reason, the digits inthe depth window flash on and off to alert you that the unit is nottracking the bottom.Map Split Sonar Detail—select how much detail appears on theMap Page with the sonar shown. Full Range shows data using theRange setting of the Sonar Page, regardless of Zoom or BottomLock. Maximum Detail shows any Zoom or Bottom Lock datafrom the Sonar Page.Keel Offset—enter the surface reading for the depth of a keel. Thismakes it possible to measure depth from the bottom of your keelinstead of from the transducer’s location. Enter a positive numberto offset for a keel. It is also possible to enter a negative number tocompensate for a large vessel that can draw several feet of water.The Keel Offset is reflected in the depth reading.Transducer—select the type of transducer that you are using. If youare using a speed-capable transducer/sensor, select Temp, Spd.GPSMAP 378/478 Owner’s Manual 109SETTING UP AND USING SONAR > SETTING UP SONAR
