• 2X Zoom—shows the 2X zoomed picture on the full screen.• 4X Split—shows two reduced pictures, the right at theoriginal depth scale and the left at 1/4 the original depth scale.• 4X Zoom—shows the 4X zoomed picture on the full screen.• Btm (Bottom) Split—shows two reduced pictures, the rightat the original depth scale and the left showing sonar returnsfrom the bottom up. All target depths read as a distance fromthe bottom.• Btm (Bottom) Lock—shows returns from the bottom up onthe full screen.TIP: Quickly zoom in and out of the Sonar display by pressingthe In and Out keys. Turn off the zoom function by pressing theOut key until the No Zoom setting appears.View/Span—changes the viewing range of a zoomed display. If thedisplay is 2X or 4X split, only the zoomed portion on the left side ofthe display is affected by the change. If the display is Bottom Splitor Bottom Lock, Span adjusts how far off the bottom the unit showsdata. This option is available when a Zoom scale other than NoZoom is selected.Gain—allows you to control the sensitivity of the unit’s receiver.To see more detail, increase the receiver sensitivity by selecting ahigher gain. If there is too much detail select a lower gain.Target Level—adjusts colors used to show sonar information. AColor Bar appears on the right side of the screen as you adjust thissetting. A higher percentage results in more strong-signaled colorsshown on the sonar display. A lower percentage results in moreweaker-signaled colors shown on the sonar display. This setting doesnot increase or decrease the unit Gain.Whiteline—controls how the unit shows information about thebottom type (hard or soft). With Whiteline Off, the bottom returnshows as red. Set Whiteline at Normal or 1–100% to determinebottom hardness. See page 114 for more information.Frequency—allows you to choose a transducer frequency.Frequency refers to the “pitch” of the sound that the transducersends and receives.Depth Line—adds a horizontal depth line across the display that isused to measure the depth of underwater objects. The depth of theline appears in a box on the right side of the line. Press up or downon the ROCKER to move the line on the sonar display.Noise Reject—helps filter unwanted noise from the sonar display.The Noise Reject can be turned Off, set to Normal (automaticallyadjusts for optimum viewing) or to a fixed 1–100% setting. Whensetting the Noise Reject, remember that a higher noise rejectionsetting is less likely to show fish or structures.106 GPSMAP 376C Owner’s ManualSETTING UP AND USING SONAR > U SING THE SONAR PAGE190-00508-00_0C.indd 106 11/6/2006 9:47:42 AM