Chapter 7: Using The Fishfinder; Introduction; How Does The Fishfinder Work - Raymarine C-Series Reference Manual

Chapter 7: Using the Fishfinder

Chapter 7: Using the Fishfinder

7.1 Introduction

This chapter describes the how Fishfinder uses sonar to see fish, bottom structure and
texture, and underwater obstructions such as wrecks.
The standard fishfinder image is a historical, scrolling bottom graph at an
automatically selected range and frequency. Various functions are provided to
improve the underwater view, select what is displayed and sound an alarm including:
• Changing the view displayed (A-Scope, Zoom or Bottom Lock)
• Pausing the scrolling image.
• Switching the depth digit on/off.
• Setting the range and frequency.
• Manually adjusting the sensitivity, color gain, time varied gain and transducer
power.
• Using waypoints to mark positions.
• Fishfinder alarms (fish, depth or water termperature ).
• Measure depth-below and distance-from-boat using a Variable Range Marker
(VRM).
Please refer to the C-Series installation manual for fishfinder calibration infor-
Note:
mation.

7.2 How does the Fishfinder work?

The fishfinder application uses a Digital Sounder Module (DSM) to process sonar
signals from a suitable transducer and provide a detailed underwater view.
The transducer located on the bottom of the boat sends pulses of sound waves into the
water and measures the time it takes for the sound wave to travel to the bottom and
back. The returning sound echoes are affected by bottom structure and by any other
objects in their path, e.g. fish, wrecks, reefs.
The Digital Sounder Module (DSM) processes these echoes and sends data to the
fishfinder which displays a visual interpretation of the underwater view. The strength
of echoes is indicated on the display by different colors. You can use this information to
determine the bottom structure, the size of fish and other objects in the water e.g.
debris, air bubbles..
Notes: (1)
(2)
The DSM will operate at a frequency of 50 kHz or 200 kHz.
Some transducers will also enable the fishfinder to display water
temperature and/or speed.
7-1