SETTING UP AND USING SONARThis section covers the additional sonar options for theGPSMAP 378/478 when used in conjunction with a GSD 21 or GSD20 Sounder Module. Read the GSD 21 or GSD 20 Sounder ModuleInstallation Instructions to properly install the sounder module.When you turn on your GPSMAP 378/478, the Sounder Moduleautomatically turns on.NOTE: You MUST have a GSD 21 or GSD 20 installed andconnected to your GPSMAP 378/478 to use the sonar features.The Sonar Page is added to the end of the page sequence when youare in Marine Mode. To view the Sonar Page, press PAGE or QUITrepeatedly until it appears.Showing Sonar on the Map PageYou can change the layout of the Map Page to show a split screento show the sonar on the Map Page. You must be in Marine Mode touse sonar.To show the Sonar Page on the Map Page:1. Press and hold PAGE/MODE.2. Highlight Marine and press ENTER.3. Press PAGE or QUIT to open the Map Page.4. Press MENU. Use the ROCKER to highlight Set Up PageLayout, and press ENTER.5. Highlight Map with Sonar and press ENTER.Map Page with Split ScreenTo resize the Map Page sonar split screen:1. After showing the Sonar and Map pages together in the splitscreen as described in the previous steps, press MENU.2. Highlight Size Split, and press ENTER.3. Use the ROCKER to move the vertical double-arrow right orleft.4. Press ENTER.5. To stop resizing the screen, press QUIT. You can also pressMENU, highlight Stop Resizing, and press ENTER to stopresizing the screen and retain the previous split setting.104 GPSMAP 378/478 Owner’s ManualSETTING UP AND USING SONAR > SHOWING SONAR ON THE MAP PAGE
