Garmin GPS 152 Owner's Manual - Page 69

• Heading- lets you select the reference used in calculating heading information. You can select from 'Auto Mag Var', 'True', 'Grid' and 'User Mag Var'. 'Auto Mag Var' provides magnetic north heading references which are automatically determined from your current position. 'True' provides headings based upon a true north reference. 'Grid' provides headings based on a grid north reference (and is used in conjunction with the grid position formats described on page 58). 'User Mag Var' allows you to specify the magnetic variation at your current position and provides magnetic north heading references based upon the variation you enter. To enter a user defined magnetic variation: 1. With the 'Heading' field set to 'User Mag Var', highlight the heading reference field (immediately to the right) and press ENTER/MARK. 2. Use the ARROW KEYPAD to enter the magnetic variation at your current position and press ENTER/MARK. , WARNING: If 'User Mag Var' is selected, you must periodically update the magnetic variation as your position changes. Using this setting, the unit will not automatically calculate and update the magnetic variation at your present position. Failure to update this setting may result in substantial differences between the information displayed on your unit and external references, such as a magnetic compass. • Distance, Speed and Altitude- lets you select the desired units of measure for distance, speed and altitude readouts in 'Nautical' (nm, kt, ft), 'Statute' (mi, mh, ft) or 'Metric' (km, kh, mt) terms. • Depth*- lets you select the desired units of measure for depth in Feet (ft), Fathoms (fa) or Meters (mt). • Temperature*- lets you select the desired units of measure for temperature in Fahrenheit (°F) or Celsius (°C). * You must be receiving proper sonar NMEA data from another device for this data to display. See pages 83-84. Reference Main Menu: Units Tab You may manually enter a magnetic variation. 59