Operation Manual
FarSounder, Inc.
F31552 (Rev. 3.8.0)
Page 60 of 69
C. 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 affect 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 echo sounders 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 partial or whole "rings" of echoes all at the same range as shown
in figure C.1. 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 figures C.2 and C.3. 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. In locations where the FarSounder
sonar is most valuable, echo sounder interference is usually not present. Generally, the FarSounder will
not interfere with echo sounders.
