Garmin GPSMAP 8530 Black Box Owner's Manual - Page 20

The range and the bearing to the target location appear in the upper-left corner of the screen. Radar Overlay When you connect your chartplotter to an optional Garmin marine radar, you can use the Radar overlay to overlay radar information on the Navigation chart or on the Fishing chart. The Radar overlay superimposes radar information on the Navigation chart or the Fishing chart. Data appears on the Radar overlay based on the most recently used radar mode (such as Harbor, Offshore, or Sentry), and all settings configurations applied to the Radar overlay are also applied to the last-used radar mode. For example, if you use Harbor mode and then you switch to the Radar overlay, the Radar overlay would show Harbor mode radar data. If you changed the gain setting using the Radar overlay menu, the gain setting for Harbor mode would change automatically. Radar Overlay and Chart Data Alignment When using the Radar overlay, the chartplotter aligns radar data with chart data based on the boat heading, which is based by default on data from a magnetic heading sensor connected using a NMEA 0183 or NMEA 2000 network. If a heading sensor is not available, the boat heading is based on GPS tracking data. GPS tracking data indicates the direction in which the boat is moving, not the direction in which the boat is pointing. If the boat is drifting backward or sideways due to a current or wind, the Radar overlay may not perfectly align with the chart data. This situation should be avoided by using boat-heading data from an electronic compass. If the boat heading is based on data from a magnetic heading sensor or an automatic pilot, the heading data could be compromised due to incorrect setup, mechanical malfunction, magnetic interference, or other factors. If the heading data is compromised, the Radar overlay may not align perfectly with the chart data. Showing the Radar Overlay The Radar overlay displays data based on the most recently used radar mode. From a Radar screen, select Menu > Radar Menu > Change Radar > Radar Overlay. The radar picture appears in orange and overlays the Navigation chart. Stopping the Transmission of Radar Signals From a Radar screen, select Menu > Radar Menu > Radar to Standby. Optimizing the Radar Display You can adjust the radar display settings for reduced clutter and increased accuracy. NOTE: You can optimize the radar display for each radar mode. 1 Select a radar range (page 14). 2 Restore the default value of the gain setting (page 14). 3 Adjust the gain setting manually (page 14). Range of Radar Signals The range of the radar signal indicates the length of the pulsed signal transmitted and received by the radar. As the range increases, the radar transmits longer pulses in order to reach distant targets. Closer targets, especially rain and waves, also reflect the longer pulses, which can add noise to the Radar screen. Viewing information about longer-range targets can also decrease the amount of space available on the Radar screen for viewing information about shorter-range targets. Radar Gain and Clutter Automatically Adjusting Gain on the Radar Screen Auto is the default value for the gain setting. The automatic gain setting for each radar mode is optimized for that mode, and may differ from the automatic gain setting used for another mode. NOTE: Depending upon the radar in use, the gain setting configured for use in one radar mode may or may not be applied to other radar modes or to the Radar overlay. From a Radar screen or the Radar overlay, select Menu > Radar Menu > Gain > Auto. The chartplotter sets the gain automatically once, based on average conditions, the range of the radar signal, and the selected radar mode. The chartplotter does not readjust the gain automatically in response to changing conditions. Manually Adjusting Gain on the Radar Screen For optimal radar performance that accounts for actual conditions, you can manually adjust the gain. NOTE: Depending upon the radar in use, the gain setting configured for use in one radar mode may or may not be applied to other radar modes or to the Radar overlay. 1 From a Radar screen or the Radar overlay, select Menu > Radar Menu > Gain. 2 Select Up to raise the gain, until light speckles appear across the Radar screen. Data on the Radar screen is refreshed every few seconds. As a result, the effects of manually adjusting the gain may not appear instantly. Adjust the gain slowly. 3 Select Down to lower the gain until the speckles disappear. 4 If boats, land, or other targets are within range, select Down to lower the gain until the targets begin to blink. 5 Select Up to raise the gain until the boats, land, or other targets appear steadily lit on the Radar screen. 6 Minimize the appearance of nearby large objects, if necessary. 7 Minimize the appearance of side-lobe echoes, if necessary. Minimizing Nearby Large-Object Interference Nearby targets of significant size, such as jetty walls, can cause a very bright image of the target to appear on the Radar screen. This image can obscure smaller targets located near it. NOTE: Depending upon the radar in use, the gain setting configured for use in one radar mode may or may not be applied to other radar modes or to the Radar overlay. 1 From a Radar screen or the Radar overlay, select Menu > Radar Menu > Gain. 2 Select Down to lower the gain until the smaller targets are clearly visible on the Radar screen. Reducing the gain to eliminate nearby large-object interference may cause smaller or distant targets to blink or disappear from the Radar screen. Minimizing Side-Lobe Interference on the Radar Screen Side-lobe interference may appear to streak outward from a target in a semi-circular pattern. Side-lobe effects can be avoided by reducing the gain or reducing the radar range. NOTE: Depending upon the radar in use, the gain setting configured for use in one radar mode may or may not be applied to other radar modes or to the Radar overlay. 1 From a Radar screen or the Radar overlay, select Menu > Radar Menu > Gain. 2 Select Down to lower the gain until the semi-circular, streaked pattern disappears from the Radar screen. Reducing the gain to eliminate side-lobe interference may cause smaller or distant targets to blink or disappear from the Radar screen. 14 Radar