GP1670F_1870F Operator's Manual - Furuno USA

7. FISH FINDER OPERATIONSItem[50 kHz BOTTOM LEVEL],[200 kHz BOTTOM LEVEL][SMOOTHING]FunctionIn the default bottom level setting (0), the equipmentjudges consecutive strong echoes to be bottom echoes.If, in that setting, the depth indication is unstable, adjustthe bottom level. If strong vertical lines extend upwardfrom the bottom echo in the bottom lock display, lowerthe bottom level to weaken the vertical lines. If the levelis too low, however, it may be difficult to distinguish bottomfish from the bottom echo.If echoes appear “spotty” adjust smoothing to smoothechoes. The higher the setting the greater the smoothing.[DEPTH INFORMATION]Hide or show the depth indication and select its size,[Large] or [Small].[SENSOR SETUP]: The [SENSOR SETUP] sub menu provides the following features.+0.0 ft+0%+0.00°F+0 m/sItemFunction[DRAFT][SPEED CALIBRATION][TEMPERATURECALIBRATION][ACOUSTIC SPEEDCALIBRATION]The default depth measurement method is the distancebetween the transducer and the bottom. To get the depthfrom the sea surface to the bottom, enter the ship’s draft.Entry of the ship’s draft is required if the bottom discriminationdisplay is used.If the speed sensor generated speed is not correct, youcan add an offset to correct the on-screen speed indication.(NMEA format speed cannot be corrected.) Forexample, if the indication is +5% faster than the actualvalue, enter -5.If the temperature sensor generated speed is not correct,you can add an offset to correct the on-screen temperatureindication. (NMEA format temperature cannotbe corrected.) For example, if the temperature indicationis 2° lower than the actual value, enter +2.The velocity of the acoustical pulse through water canvary depending on water conditions, which can affect thedepth indication. Normally, adjustment of this setting isnot necessary. If you feel the depth indication is continuouslywrong, contact a FURUNO agent or dealer for advice.7-21