Garmin AQUAMAP 80 Series, Owner'S Manual

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.

Stopping the Transmission of Radar Signals

From a Radar screen, select 

MENU

 > 

Radar to Standby

.

TIP: 

Press   from any screen to quickly stop radar 

transmission.

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 (

Range of Radar Signals

, page 20

).

2

Restore the default value of the gain setting (

Adjusting Gain 

on the Radar Screen Automatically

, page 20

).

3

Adjust the gain setting manually (

Adjusting Gain on the 

Radar Screen Manually

, page 20

).

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

Adjusting Gain on the Radar Screen Automatically

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.

NOTE: 

Not all options and settings are available on all radar and 

chartplotter models.

1

From a Radar screen or the Radar overlay, select 

MENU

 > 

Gain

.

2

Select an available option:
• Select 

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 adjust 

the gain automatically in response to changing conditions.

• Select 

Auto Harbor

 or 

Auto Offshore

.

The chartplotter automatically adjusts the gain for the 

conditions.

Adjusting Gain on the Radar Screen Manually

For optimal radar performance, 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

 > 

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

 > 

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

 > 

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.

20

Radar