IMPACT SUBSEA
INNOVATIVE UNDERWATER PRODUCTS
www.impactsubsea.com
Document No:
0000.1991 |
Version No:
1.6 | 6
th
October 2020
27
6.0 Theory of Operation
6.1 Sonar – Basic Principles
The ISS360 is a mechanically scanned imaging SONAR (SOund NAvigation and Ranging).
This is an active sonar which operates by transmitting a pulse of sound into the water; then
listening for and plotting the returned echoes that are reflected by items in the water.
The sonar emits a pulse of sound which is 23° high and 2.2° wide. Any item which falls within this
pulse of sound will be detected and plotted on screen.
The sonar image is built up by rotating a transducer in the boot end. The transducer emits a pulse
of sound (a ‘Ping’) and listens for any returning echoes across the defined measurement range.
Once complete, the transducer is rotated by a step (size defined in the software) and the process
repeats.
Through the ‘Ping’, ‘Listen’, ‘Step’ processes: a 2D, top down image is produced on screen.
There are a number of books and resources available online which explore sonar image
interpretation in detail. It is assumed the user of the ISS360 is familiar with basic sonar image
interpretation, so detail is not provided here.
Acoustics (also known as hydro-acoustics, or sound pressure waves) are used by the ISS360 Sonar
due to their high efficiency in travelling long distances through water. Through-water acoustics can
travel far greater distances than signals in the light or radio frequency spectrum. Thus, are the
ideal method to use for visualising the underwater environment.
The ISS360 Sonar operates by emitting an acoustic pulse into the
water. This pulse travels through
the water until it comes into contact with the seabed or other objects. Upon contact with the
seabed/objects, part of the pulse is absorbed, and part is reflected back to the ISS360 sonar.
This reflected portion is detected by the ISS360 and the time taken for this acoustic pulse to travel
from the ISS360 Sonar, bounce off the seabed and return is recorded.
