Raymarine E120W, Reference Manual

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Chapter 7: Using the Radar 141
Chapter 7: Using the Radar
7.1 Introduction
This chapter describes the basics of radar and the things that can affect your radar
picture. It then shows you how to use your radar and its various functions including:
• Changing orientation and motion mode.
• Getting the best radar picture.
• Measuring distances and bearings.
• Collision avoidance using Guard Zones, MARPA and AIS.
• Using waypoints to mark positions.
• Setting up the radar display.
• Radar alarms.
• View AIS data.
7.2 What is radar?
Radio Detection And Ranging (RADAR) is something that is in use all around us,
although it is normally invisible. One of the most common uses of radar at sea is to
detect the presence of objects, known as ‘targets’ at a distance, and if they are moving,
detect their speed.
This chapter of the Reference manual provides the information and instructions to
enable you to start using the radar so that you know what is around you and use the in-
built Mini Automatic Radar Plotting Aid (MARPA) functions to help in collision
avoidance.
Until you are familiar with interpreting the radar display, every opportunity should be
taken to compare the radar screen patterns with visual targets, such as other boats,
buoys and coastal structures. You should practise harbor and coastal navigation
during daylight hours and in clear weather conditions.
Detecting targets
Radar works by transmitting radio pulses, then detecting reflections of these pulses
(echoes) from objects in the area and displaying the reflections as targets on your
display.