Operation Manual
FarSounder, Inc.
F31552 (Rev. 2.6.1)
Page 45 of 56
A. Understanding Interference and Other
Limitations
1. Overview
FarSounder has developed advanced signal processing algorithms that allow the software to operate largely
without significant user input. These algorithms represent the state of the art in forward looking, obstacle
avoidance sonar technology. However, like any shipboard tool, Forward Looking Sonar will not solve every
problem 100% of the time. It will, however, solve many problems most of the time. It is therefore important
to accurately understand how interference and other limitations effect the system's performance.
2. Other Sonar Interference
FarSounder's sonars operate at around 60 kHz. The most common echo sounder frequency is 50 kHz.
Since these frequencies are close to one another, users may sometimes experience interference from other
sonars. Generally, interference is only experienced when the echosounders on large commercial ships are
close to the user's vessel and when the FarSounder is pointed towards the other ship. Such interference
appears on the FarSounder display as a “ring” of echoes all at the same range as shown in Figure A.1,
“Echo sounder interference”. Usually, they appear as in-water targets, but sometimes they can also appear
as a raised mound or sharp dip in the sea bottom at all angles. The interference can also be seen in
the System Status's Hydrophone Data display as shown in Figure A.2, “Echo sounder interference” and
Figure A.3, “Echo sounder interference”. In this view, the interference appears as sharp “spikes” in the
signal at regular intervals. Generally, between 6 and 20 spikes will be present at a time in the Hydrophone
Data Display. It is important to realize that if another vessel is interfering with the FarSounder sonar, this
usually means the area is well trafficked and often well known. Locations where the FarSounder sonar is
most valuable, echosounder interference is usually not present. Generally, the FarSounder will not interfere
with echosounders.
