Garmin GPSMAP 820 Owner's Manual - Page 21

traditional transducers or the contrast for DownVü and SideVü/ DownVü transducers. This setting works best after you have adjusted the level of detail shown on the screen using the gain or brightness settings. If you want to highlight smaller fish targets or create a higher intensity display of a target, you can increase the color gain or contrast setting. This causes a loss in the differentiation of the high intensity returns at the bottom. If you want to reduce the intensity of the return, you can reduce the color gain or contrast. 1 From a sonar view, select MENU. 2 Select an option: • While in the DownVü or SideVü sonar view, select Contrast. • While in another sonar view, select Sonar Setup > Advanced > Color Gain. 3 Select an option: • To increase or decrease the color intensity manually, select Up or Down. • To use the default setting, select Default. Adjusting the Range of the Depth or Width Scale You can adjust the range of the depth scale traditional and DownVü sonar views and the range of the width scale for the SideVü sonar view. Allowing the device to adjust the range automatically keeps the bottom within the lower or outer third of the sonar screen, and can be useful for tracking a bottom that has minimal or moderate terrain changes. Manually adjusting the range enables you to view a specified range, which can be useful for tracking a bottom that has large terrain changes, such as a drop-offs or cliffs. The bottom can appear on the screen as long as it appears within the range you have set. 1 From a sonar view, select MENU > Range. 2 Select an option: • To allow the chartplotter to adjust the range automatically, select Auto. • To increase or decrease the range manually, select Up or Down. TIP: From the sonar screen, you can select or to manually adjust the range. Setting the Zoom Level on the Sonar Screen 1 From a sonar view, select MENU > Zoom. 2 Select an option: • To zoom in on the sonar data from the bottom depth, select Bottom Lock. • To set the depth range of the magnified area manually, select Manual, select View Up or View Down to set the depth range of the magnified area, and select Zoom In or Zoom Out to increase or decrease the magnification of the magnified area. • To set the depth and zoom automatically, select Auto. • To cancel the zoom, select No Zoom. Sonar Frequencies NOTE: The frequencies available depend on the chartplotter, sounder modules, and transducer being used. Adjusting the frequency helps adapt the sonar for your particular goals and the present depth of the water. Higher frequencies use narrow beam widths, and are better for high-speed operation and rough sea conditions. Bottom definition and thermocline definition can be better when using a higher frequency. Lower frequencies use wider beam widths, which can let the fisherman see more targets, but could also generate more surface noise and reduce bottom signal continuity during rough sea conditions. Wider beam widths generate larger arches for fish target returns, making them ideal for locating fish. Wider beam widths also perform better in deep water, because the lower frequency has better deep water penetration Chirp frequencies allow you to sweep each pulse through a range of frequencies, resulting in better target separation in deep water. Chirp can be used to distinctly identify targets, like individual fish in a school, and for deep water applications. Chirp generally performs better than single frequency applications. Because some fish targets may show up better using a fixed frequency, you should consider your goals and water conditions when using Chirp. Some sonar black boxes and transducers also provide the ability to customize preset frequencies for each transducer element, which enables you to change the frequency quickly using the presets as the water and your goals change. Viewing two frequencies concurrently using the Split Frequency view, allows you to see deeper with the lower frequency return and at the same time see more detail from the higher frequency return. Selecting Frequencies NOTE: You cannot adjust the frequency for all sonar views and transducers. You can indicate which frequencies appear on the sonar screen. 1 From a sonar view, select MENU > Frequency. 2 Select a frequency suited to your needs and water depth. For more information on frequencies, see Sonar Frequencies. Creating a Frequency Preset NOTE: Not available with all transducers. You can create a preset to save a specific sonar frequency, which allows you to change frequencies quickly. 1 From a sonar view, select MENU > Frequency. 2 Select Add. 3 Enter a frequency. Turning On the A-Scope NOTE: This feature is not available in all sonar views. The a-scope is a vertical flasher along the right side of the fullscreen sonar view. This feature expands the most recently received sonar data so that it is easier to see. It can also be helpful for detecting fish that are close to the bottom. From a sonar view, select MENU > Sonar Setup > Appearance > A-Scope. Selecting the Transducer Type Before you can select the transducer type, you must know what kind of transducer you have. If you are connecting a transducer that was not included with the chartplotter, you may need to set the transducer type to make the sonar function properly. If the device automatically detected your transducer, this option does not appear. 1 From a sonar view, select MENU > Sonar Setup > Installation > Transducer Type. 2 Select an option: • If you have a 200/77 kHz, dual-beam transducer, select Dual Beam. Sonar 15