Garmin GPSMAP 392, 398, 492, 498 Owner's Manual

Also see for GPSMAP 392, 398, 492, 498: Quick reference guide Specifications

Contents

80 GPSMAP 392/398/492/498 Owner’s ManualU SING SONAR > U NDERSTANDING SONARAuto Color Gain—controls what colors are applied to the objectson the screen. Color DCG is based on depth and makes it easier tospot subtle changes in bottom conditions or fish sizes. DynaColor(default) represents the latest in sonar data presentation and isrecommended for all applications. The presentation is based onbottom strength. It makes the bottom and the fish easier to see andrequires fewer adjustments.Automatic Gain Level—controls the aggressiveness of the AutoGain. The higher the setting, the greater the number of targetsappear on the screen. The lower the setting, the less clutter on thescreen. The settings are Low, Medium (default), and High.Automatic Scroll Speed Limit—automatically adjusts the Scrollrate (see page 76) with the speed of your vessel. Entering yourmaximum cruising speed produces a 100% scroll rate when youreach that speed. One half of that speed produces a 50% scroll rate,and so on. The default is 30.0 kt.Transducer Type—allows you to specify what type of transduceryou are using, either Dual Beam or Dual Frequency..Calibrate Water Speed—this appears only if you are using aspeed-capable transducer/sensor. Calibration is required to ensurethat the Water Speed shown on your unit is accurate. The unitautomatically uses GPS ground speed for comparison on thecalibration. If a GPS ground speed is not available, use either yourboat’s speedometer reading (not always accurate) or a stopwatchto determine your speed over a certain distance (distance / time =speed). It is recommended that the calibration take place in waterhaving little or no current.