58 GPSMAP 3005C Owner’s ManualM AIN MENU > SYSTEM TABSliders5. Press up or down on the ROCKER to increase or decrease the backlightlevel, and press ENTER.6. To adjust the offset minutes, select the minutes field, and press ENTER.7. Enter the offset minutes for Before Sunrise or After Sunset. If zero, theunit automatically changes to the specified level at sunrise/sunset. PressQUIT to exit.Units Sub TabUse the Units sub tab to define settings for Position Format, Depth, Map Datum,Temperature, Distance, Speed, and Elevation, Pressure, and Heading.WARNING: The Units sub tab settings affect how navigation informationappears on the GPSMAP 3005C. If you are using a map or chart with yourGPS, make sure the settings on the Units sub tab match that of the map orchart. This information should be shown somewhere on the map or chart. Ifnot, contact the map or chart maker to determine what position format, datum,heading, and units of measure are used for the map or chart.The following settings are available:• Position Format—used to change the coordinate system in which a givenlocation reading appears. Only change the position format if you are usinga map or chart that specifies a different position format or you want to use aformat you are familiar with. The default format is latitude and longitude indegrees, minutes, and thousandths of a minute (hddd°mm.mmm’).• Depth—select the units of measure for depth in Feet (ft), Fathoms (fa),or Meters (m). You must be receiving NMEA Sonar depth data or using aGarmin sonar module for the depth to appear.
