Table Of ContentRADAR AND
ARPA MANUAL
RADAR AND
ARPA MANUAL
Radar, AIS and Target Tracking
for Marine Radar Users
THIRD EDITION
A B
LAN OLE
Radar/ARPAnauticalconsultantandformerPrincipalLecturer
inNavigationSystemsatLiverpoolJohnMooresUniversity,UK
A W
LAN ALL
HeadofNauticalScienceandCo-directorofLiverpoolLogistics
Offshore&MarineResearchInstitute,LiverpoolJohnMooresUniversity,UK
A N
NDY ORRIS
MaritimeConsultantandHonoraryProfessorforNavigationTechnology,
UniversityofNottingham,UK
AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON
NEWYORK(cid:129)OXFORD(cid:129)PARIS(cid:129)SANDIEGO
SANFRANCISCO(cid:129)SINGAPORE(cid:129)SYDNEY(cid:129)TOKYO
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Dedication
To Bill and Keith
Preface to the Third Edition
There have been considerable advances in In recent years, there have been consider-
technology in recent years which has meant able changes and increases in the technical
that a major revision hasbeen necessary. specifications of all navigational equipment
In the past, much of the work of the naviga- (although rarely retrospective), and also, the
tor involved the correct use of the controls in Carriage Requirements. These have, to a large
setting up the display and the correct interpre- extent, been taken into account in this treat-
tation of the displayed data (cid:1) in particular, ment. Also, the basic ideas behind solid-state
radar plotting to determine risk of collision. coherent radars have been included within
These problems have been largely solved by Chapter 2, as these are being increasingly fit-
the development of digital techniques which tedto vessels.
have allowed the data to be electronically pro- IMO and national advice on matters of
cessed resulting, among other facilities, in safetyandgood practice isstill includedwhere
auto-clutter suppression and target tracking applicable. The correct use of the equipment is
(ARPA). paramount and it is in this area that we have
Unfortunately, the advances in technology continued to stress the importance of ‘good
have brought with them their own problems. practice’ which has been built up over the
The move from analogue to digital techniques years.
has opened up considerable possibilities, in Although small vessels and pleasure craft
particular, to integrate the displayed outputs are not specifically required to carry this
from what were independent instruments on equipment, many of them do and in their
to a common display monitor. This can give interest; it is hoped that many aspects of the
rise to information overload and/or display material covered here will prove of value for
congestion ifused indiscriminately. them.
A common failing now is for operators not Some material relating to the development
to input, update or regularly check the data of radar has been retained in order to pro-
being fed to the systems upon which the out- vide a background to understand where
put depends (courses, speeds, ship’s data, today’s equipment is coming from and to
etc.). As a result, for the navigator, the dis- underpin the theory upon which present-day
played data can be erroneous/misleading. The radars are based. Most of the descriptions
behaviour of an observer on another vessel which related to specific earlier equipment
will depend on the information being received has been removed, in spite of the fact
(e.g. from AIS) and from information deter- some of that equipment may still be in use
mined (e.g. from radar/ARPA). Serious confu- today.
sion can arise when there are inconsistencies Another significant change is that the latest
in what the instruments are telling the IMO performance standards for radar on ships
observer. no longer refer to the term ARPA and instead
xv
xvi
PREFACETOTHETHIRDEDITION
use the term Target Tracker, as the equipment AlanBole
now has to integrate and present AIS Radar/ARPA nauticalconsultant and former
(Automatic Identification System) data with PrincipalLecturer in NavigationSystems at
radar tracked data. This new edition has there- Liverpool John MooresUniversity, UK
fore included a much larger discussion of AIS Alan Wall
with the inclusion of the new Chapter 5. This Head of Nautical Science and Co-directorof
trend away from independent to integrated Liverpool Logistics Offshore & Marine Research
equipment has meant that, for completeness, Institute,Liverpool John MooresUniversity, UK
the inter-relationship between radar/ARPA, Andy Norris
AIS, GPS and ECDIS has had to be included, MaritimeConsultant and Honorary Professor
but not to the same technical depth as the for Navigation Technology, Universityof
radar and ARPA. Nottingham, UK
Acknowledgements
First edition Wall in proofreading the manuscript and for
Theauthorswishtoexpresstheirgratitudeto: their help, support and encouragement in our
The International Maritime Organization completion ofthis book.
(IMO) for permission to reproduce the vari- Mr B. Price of Sandown College, Liverpool,
ous extracts from resolutions adopted by the for his helpful comments based on a reading
Assembly. of Chapter 2.
The Controller of Her Majesty’s Stationery Mr Andrew O. Dineley for his assistance
Office for permission to reproduce the extracts in producing the computer printout of the
from M 1158 and Statutory Instrument No. manuscript.
1203 (1984). Familiesandfriendswithoutwhoseassistance,
CaptainC.E.NichollsofLiverpoolPolytechnic support and understanding, this undertaking
forhismajorcontributiontoChapter8. wouldneverhavebeencompleted.
Second edition Thirdedition
WeagainexpressourthankstoIMOforper- Mr Barry Wade of Kelvin Hughes for his
mission to reproduce updated extracts from helpful comments on Chapter2.
variousresolutionsadoptedbytheAssembly. We again express our thanks to IMO for
In this edition we are grateful for the con- permission to reproduce updated extractsfrom
siderable assistance of June Bole and Alison variousresolutionsadoptedbytheAssembly.
xvii
C H A P T E R
1
Basic Radar Principles
1.1 INTRODUCTION was used to determine the height of the iono-
sphere in the mid-1920s, it was not until 1935
Radar forms an important component of the that radar pulses were successfully used to
navigational equipment fitted on virtually all detect and measure the range of an aircraft. In
vessels apart from the very smallest. Its display the 1930s there was much simultaneous but
of critical information is easily assimilated by a independent development of radar techniques
trained user and has acted as a focus for the in Britain, Germany, France and America.
presentation of other navigational data, giving Radar first went to sea in a warship in 1937
it a deserved prominence on the bridge of a and by 1939 considerable improvement in per-
vessel. It ispoised to retain its central electronic formance had been achieved. By 1944 naval
navigational role into the foreseeable future, radar had made an appearance on merchant
equalled only in display significance by the ships and from about the end of the Second
rather more recent development, the electronic World War the growth of civil marine radar
chart. Together, they will provide the basis of began. Progressively it was refined to meet the
the major displays for marine navigation into needs of peacetime navigation and collision
anincreasinglyintegratednavigationalworld. avoidance.
The word RADAR is an acronym derived The civil marine radars in use today differ
from the words Radio Detection and Ranging. markedly from their ancestors of the 1940s in
The scientist Heinrich Hertz, after whom the size, appearance and versatility, but the basic
basic unit of frequency is named, demon- data that they offer, namely target range and
strated in 1886 that radio waves could be bearing, are determined by exploiting the same
reflected from metallic objects. In 1904 a fundamental principles unveiled so long ago.
German engineer, Christian Hu¨lsmeyer, An understanding of such principles is an
obtained a patent in several countries for a essential starting point in any study of marine
radio wave device capable of detecting ships, radar, even though recent developments in the
but it aroused little enthusiasm because of its use of a technology known as coherent radar
very limited range. Marconi, delivering a lec- have somewhat complicated the picture. This
ture in 1922, drew attention to the work of latter technology is explained in some detail in
Hertz and proposed in principle what we Section2.9,butfirstitisusefultogainanunder-
know today as marine radar. Although radar standingofthebasicprinciplesbehindradar.
RadarandARPAManual. 1 ©2014ElsevierLtd.Allrightsreserved.
2
1. BASICRADARPRINCIPLES
1.2 PRINCIPLES OF RANGE AND C. Shortshouts are required if echoes from
BEARING MEASUREMENT closetargets are not tobe drowned by the
original shout.
1.2.1 The Echo Principle D. A sufficiently long intervalbetweenshouts
is required to allow time for echoes from
An object (normally referred to as a target)
distant targets to return.
is detected by the transmission of radio energy E. It can bemore effective tocupone’s hands
as a pulse or otherwise, and the subsequent
over the mouth when shouting andput a
reception of a fraction of such energy (the
hand to theear whenlistening for theecho.
echo) which is reflected by the target in the
direction of the transmitter. The phenomenon Now considering radar, its basic building
is analogous to the reflection of sound waves blocks are illustrated diagrammatically in
from land formations and large buildings. Figure 1.1. The antenna is used both to trans-
Imagine somebody giving a short sharp shout mit the signal and to receive its reflection. On
through cupped hands to focus the sound transmit, the antenna is acting very much like
energy. The sound wave travels outwards and the cupped hand, focussing the energy in a
some of it may strike, for example, a cliff. particular direction. On receive it is acting
Some of the energy which is intercepted will more like a hand to the ear, collecting more
be reflected by the cliff. If the reflected energy received energy from that direction. The trans-
returns in the direction of the caller, and is of mitter has a similar role to that of the mouth
sufficient strength, it will be heard as an audi- and vocal chords of the shouter, and the radar
ble echo, resembling the original shout. In con- receiver acts as the ear. The processor clarifies
sidering this analogy, the following points can the received signal and judges its distance,
usefully assist in gaining a preliminary under- perhaps somewhat similar to what a trained
standing of pulse radar detection: human brain can do in identifying and asses-
sing a received sound wave. Finally the radar
A. The echo isneveras loud as the original displays the information to a human operator,
shout. perhaps analogous to a human writing down
B. The chance of detectingan echo depends the estimated range and direction of the object
on theloudness andduration ofthe shout. producing the echo.
Antenna
Receiver
Signal Display and
Switch Processor
amplification user interface
Transmitter
FIGURE1.1 Thebasicradarsystem.
RADARANDARPAMANUAL
3
1.2PRINCIPLESOFRANGEANDBEARINGMEASUREMENT
The antenna of a marine radar rotates simple general relationship between target
steadily in the horizontal plane giving a com- range and the elapsed time which separates
plete rotation about every 2s. This means that the transmission of the pulse and the reception
radar pulses consecutively cover all directions of an echo inany particularcase (Figure 1.2).
over 360(cid:1) at each rotation of the antenna. The Let D5the distance travelled by the pulse
speedofradiowavesissohigh, about onemil- to and from the target (metres)
lion times greater than sound waves, that the
R5the range of the target (m)
antenna receives all the reflected energy from
T5theelapsedtime (µs)
a particular transmitted pulse before it has
S5thespeed ofradio waves (m/µs)
appreciably rotated.
Then D5S3T
1.2.2 Range as a Function of Time and R5(S3T)/2
henceR5(3003T)/2
It is self-evident that the time which elapses thus R5150T
between the transmission of a pulse and the
The application of this relationship can be
reception of the corresponding echo depends
illustrated by thefollowing example.
on the speed of the pulse and the distance
which it has travelled in making its two-way
journey. If the speed of the pulse is known
EXAMPLE 1.1
and the elapsed time can be measured, the
Calculate the elapsed time for a pulse to
range of the target producing the echo can be
travel to and return from a radar target whose
calculated.
rangeis(a)40m(b)12nauticalmiles(NM).
The velocity of radio waves is dependent on
the nature of the medium through which they a. R5150T
travel. In fact, within the Earth’s atmosphere it thus405150T
is hardly different to that within a space-type henceT540/150(cid:3)0.27µs
vacuum, that is 299,792,458m/s. In our own Thisvalueisofparticularinterestbecause40m
minds this is easiest to be considered to be representstheminimumdetectionrangethat
almost precisely 300,000,000 (three hundred mustbeachievedtoensurecompliancewith
million) metres per second, or as 300metres IMOPerformanceStandardsforRadar
per microsecond (µs), where 1µs represents Equipment(seeSection11.2.1).Whilethistopic
one millionth part of a second (i.e. 1026s). willbefullyexploredinSection3.2.4,itis
Using this value it is possible to produce a usefulatthisstagetonotetheextremelyshort
Distance = Speed × Time Continuing
transmitted pulse
Returning echo
D = 2 × range
R
Speed × Time
Range =
2
FIGURE1.2 Theechoprinciple.
RADARANDARPAMANUAL
