International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 4

Number 1

March 2010

1 INTRODUCTION

In this changing environmental world of Global

Warming, energy exploration and eco-tourism, new

[unexplored and uncharted] waters are being opened

up on a regular basis.

Figure 1. Victim of an accident in the ice

Here we take the opportunity to look at how an

existing technology can be adapted as a useful, im-

portant and standard part of the bridge navigation

inventory.

Figure 2. Victim of the poor navigation

FarSounder is a developer and manufacturer of

3D Forward Looking Sonar systems for use as ship

borne navigation devices as well as ship borne/shore

side security devices. This three dimensional sonar

technology offers a paradigm shift in how mariners

navigate on the water by economically, accurately

and efficiently delivering to mariners the critical in-

formation they need to safely navigate their vessels.

By providing a real-time, 3D picture of the depths

immediately ahead of a vessel, this technology can

enable marine vessel operators to avoid costly, dan-

gerous and environmentally damaging collisions and

groundings. The introduction of a navigation grade

sonar system has an important equivalence to the in-

troduction of marine radar systems during the later

part of the 20th century. With the introduction of

this enabling technology, these new systems are al-

ready changing the way mariners navigate through

the oceans.

2 CURRENT NAVIGATION TECHNOLOGIES

Current navigation technologies, such as GPS, RA-

DAR and electronic charts, are widely accepted and

are now required equipment on most classes of ves-

sels. Until now, state-of-the-art navigation has been

to rely on historical charts, GPS systems, and depth

sounders to determine position and water depth un-

der the ship. Chart data is often inexact as coastlines

and shipping channels can shift. Transient objects

such as sandbars, lost shipping containers, ship

wrecks, whales, floating logs and other debris are

not shown on charts. Additionally, many charts can

be based on data that is 60 years old or more and

predate GPS. This means that even "charted" obsta-

cles are not necessarily where the chart places them.

While an echosounder will tell the ship how deep

the water was they just passed through, it can do

3d Sonar for Navigation and Obstacle

Avoidance

I. Bowles

FarSounder, Inc. Warwick, USA

Z. Markowski

Escort Ltd. Szczecin, Poland

nothing to warn of the dangers ahead. The radar can

only tell the user about objects above the water and

give no indication of water depth.

The introduction of and use of navigation grade

Forward Looking Sonar is not meant to replace these

valuable devices, but rather to augment the mariner's

box of navigation tools by offering a real time pic-

ture of the waters ahead of the vessel. This further

enables the mariner to make critical navigation deci-

sions giving a more complete understanding of the

real time scenario.

3 CURRENT SONAR TECHNOLOGIES

Until the advent of these new 3D systems, vessel

operators were limited to one- or two-dimensional

views, with limited distance capabilities, limited per-

formance in shallow waters, and a narrow field of

view. Usually these products are from a recreational,

fishing specific or hydrographic market, and there-

fore not suited for commercial applications or useful

navigational purposes; yet they may still be market-

ed and sold for this purpose. At the other end of the

spectrum there are military grade sonar systems, that

again, are designed for a specific market capability.

They also tend not to be commercially viable navi-

gation options for a commercial vessel operator.

Although customers of these other systems un-

derstand the need, these products do not solve the

problem.

4 PRINCIPLE OF OPERATION

The 3D sonar is comprised of a phased array trans-

ducer that will usually be mounted in the bow or

stem of the vessel, facing forward. This in turn is

connected by a special cable to a junction box and

from there to the processor on the bridge.

Figure 3. Full sonar set

The forward looking horizontal field of view is a

practical 60° to 90° with a range of ¼ nm. Develop-

ment is currently underway to introduce ½ nm sys-

tem during mid 2009. Vertical field of view is ap-

proximately 10° up to the surface and 50° down. The

whole volume is pinged every second with an over-

all refresh of around 1.5 to 2 seconds giving a virtual

real time presentation.

Figure 4. Transducer usually is mounted in the bow

Figure 5. Sonar display 2D view

Figure 6. Sonar display 3D view

Figure 7. Breakwater in front

Figure 8. Barrier echogram in 3D

The advantage of three dimensions is that the ver-

tical dimension of depth is now added to the range

and bearing information.

Shallow water operation is also greatly improved.

With bottom mapping capability of 8 x the depth of

water (in practice 10 – 12 x), “in water” targets can

still be detected to the full range of the system.

An easy to use man machine interface allows for

easy interpretation of essential data.

In a comparison of the visual picture vs sonar, the

below example shows a breakwater as seen through

the bridge windows and the same view on the 3D

Forward Looking Sonar.

It is clear on the sonar display that there are other

obstacles in front of the breakwater but below the

surface.

5 ENVIRONMENTAL CONCERNS

Shipstrike is the largest killer of the endangered

Right Whale and the Great Whale. At certain times

of the year during migration patterns, certain ocean

areas are now restricted for passage or by signifi-

cantly reduced speeds.

Figure 9. Victim of the ship strike

Figure 10. Victim of the bow strike

It is also commonly reported that sonar is harmful

to marine mammal life, and it needs to be clarified

that this is often in relation to low frequency and

high power systems used predominantly for military

applications.

FarSounder sonar systems should not be confused

with these other sonar systems.

"NOAA's Ocean Acoustics Program (NMFS Of-

fice of Science and Technology) has assessed the

technical specifications of the current version of the

FarSounder sonar technology and concurs that,

based on the sound source level, signal duration, di-

rectionality, and operational frequency band, there

are no anticipated injurious effects on marine mam-

mals or other marine species from it's deployment."

“The FarSounder, high frequency, active sonar

technology may provide an effective tool in alerting

mariners to the presence of submerged, or surfac-

ing, animals in sufficient time to avoid collisions.”

Figure 11. Quieter than a dolphin and in the same frequency

range as other accepted marine electronics

6 INTEGRATION

3D sonar data can now be integrated into today’s so-

phisticated bridge management systems and was the

next logical step. Today’s IBS can now have sonar

overlay as an option to the radar overlay on the elec-

tronic chart.

With the advent of Voyage Data Recorders, more

and more recording capability is often sought. Sonar

data is no different and can also be archived, either

directly or in conjunction with the VDR.

7 LIMITATIONS AND EXPECTATIONS

Targets such as containers, whales, rocks, reefs,

ice/icebergs, other vessels, buoys, pilings, etc. (to an

8 dB target), are the benchmarks for the types of tar-

gets that can be expected to be detected.

Limitations for commercial vessel operators of all

classes are usually related to speed and range. Larger

vessels and High Speed vessels need sufficient time

to evaluate potential dangers and act accordingly,

although for vessels at manoeuvring speeds, the

range requirement is significantly less.

Current vessel speed for both the ¼ and ½ nm

systems is up to 20 to 25 knots. Future research and

development over the next 1.5 to 2 years anticipates

ranges of 1 to 2 nm and a speed up to 35 knots.

Figure 12. Catamaran equipped with 3D sonar

Figure 13. Transducer installed on the bow of a hulk

8 CHALLENGES

In regards to the development of a long range/high

speed navigation sonar as discussed above, there are

specific physical (scientific) challenges that must be

dealt with that are of minimal effect on the current

shorter range systems.

For instance, there is a trade-off in choosing an

appropriate frequency which will still offer enough

signal to noise ratio (SNR) to counter the effects of

long range attenuation of the system.

At higher speeds, a challenge to overcome may

be hull specific in dealing with high speed flow

noise issues. Therefore, the form factor of the

Transducer Module and how it is mounted must be

carefully chosen for different high speed hull types.

At short ranges it may be appropriate to regard

the Sound Speed Profile as a constant (for naviga-

tion grade sonars, not necessarily for security sonar

systems). At longer ranges, a vertically varying

sound speed profile must be compensated for.

The resolution of Long Range Targets is also a

challenge and requires an added level of Bathymet-

ric Testing and Ground Truthing as well as compen-

sation in the Fixed Frame of Reference.

9 OTHER APPLICATIONS

Future Security Applications: One of the greatest

threats to passenger vessels is an attack by swim-

mers, divers, or other underwater threats. Various

technologies enable surveillance and deliver security

against air and land attacks, but there is a lack of a

low-cost practical and effective solution to detect or

deter an underwater based attack, particularly one by

swimmers. Underwater security is one of the most

technologically challenging. Threats below the water

are difficult to address.

There is a current need in the industry for an ac-

curate, easy to use, low cost system with 360-degree

sector coverage. Three dimensional forward-looking

sonar technology can be very effectively applied to

solve this need and to combat these possible attacks.

10 CONCLUSION

The need for a navigational solution to groundings

and collisions has been recognized for hundreds, if

not thousands of years. We expect that navigation

grade sonar will become increasingly attractive to

operators of all large ships. Three dimensional sonar

technology represents an extraordinary advance in

sonar technology, and represents a revolutionary

change in the way vessels navigate.

Link to download a demo of the operator soft-

ware http://www.farsounder.com/products/demo