539
1 INTRODUCTION
Theturnofthe21
st
centuryhaswitnesseda scientific
and technological revolution in the global fleet. Entire
classes of navigation equipment and systems have
been withdrawn, e.g.Loran A and Loran C, Decca,
Omegaandradiodirectionfinders.
A classical method of ship navigation at sea –
celestial navigation – completely lost its former
import
anceintheglobalfleet.
The satellite navigation systems GPS, DGPS,
GLONAS, EGNOS have solved the problem of the
discreteness of observation and continually raise
their accuracy in comparison to the former satellite
systemTransit.
Thewidespreadadoptionofintegratednavigation
systems on ships, such as ARPA, VTS, AIS largely
relieved navigators from routine work, and in the
near fut
ure we may expect total elimination of
laborious routine work with paper charts thanks to
theimplementationofECDIS.Alltheseachievements
aretheresultsofenormousprogressofsatelliteand
computertechnologyinrecentyears.
Rapid scientific and technological progress
requires a
ppropriate actions at legal, economic and
education levels. The outdated regulatory
inconsistencies with the technical realities of today
lead to unreasonable financial costs of production,
andhavenegativeimpactonscientificresearch and
educationalprocesses.
2 VOYAGESTAGES,NAVIGATIONALTOOLS
ANDMETHODS
Thevoyageofamodernshipcanberoughlydivided
int
othreestages:
limitedportwaterarea;
coastalandoffshorewaters;
oceanicroute.
Thefirstvoyagephaseisthemostintenseinterms
of navigatorʹs work because of the proximity of
navigationaldangers.Statistically,mostnavigational
accidents occur in restricted waters of port and it
s
vicinity. Navigation in this case relies mainly on
visualandradarobservation.
Magnetic Compass in Modern Maritime Navigation
E.Lushnikov
M
aritimeUniversityofSzczecin,Poland
ABSTRACT:Thisarticle looksintothe roleofmagnetic compassinproviding the navigationalsafetyofthe
ship. Existing requirements for the magnetic compass at the presence of satellite navigation are not
economicallyjustified.Therefore, anewrational requirementisproposed fortheaccuracyand frequency of
deviationcompensationworkassuringthesafetyofnavigationandcost‐effectiveness.Theproposedmethod
hasbeenverifiedbyalabexperiment.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 4
December 2015
DOI:10.12716/1001.09.04.10
540
The second phase, coastal navigation, uses all
types of navigational equipment for shipʹs steering
andcontrol.Keepingthevesselonagivencourseis
carried out with the aid of gyrocompass, while
movementparameters arecontrolledbyallavailable
means,includingRADARandGPS.
Thethird,oceanicvoyagephaseisusuallytheleast
stressful, limit
ed to keeping the vessel on the right
track. This phase of navigation makes use of a
gyrocompass,andgyrocompasserrorsaredetected
by using a magnetic compass. Satellite navigational
systems GPS (DGPS), GLONASS, EGNOS allow at
any time to monitor the position of the vessel with
highaccuracy.
3 MAINTASKSOFMARINENAVIGATION
The prima
ry tasks of navigation are precise position
fixing and precise keeping the vessel on a given
course. These objectives are to be met quickly and
reliably.
Theaccuracyofkeepingthevesselonasetcourse
in the oceanic voyage pha
se (the longest one)
depends on the accuracy of gyrocompass and
autopilot, as well as the accuracy of determining
externalfactors(windanddrift,icefields).
Themosttypicalandcommongyrocompassesof
thetwentiethcenturywereCourse‐4andStandard‐14,
which had non‐fixed axis of hydrostatic suspension
ofpickup. Theyhadlowspeedtesttra
ckingsystem
(4
0
/sand8
0
/s,respectively).
The mean time between failures of the sensitive
element [6, 7] was 12‐15 thousand hours. The
standarderrorwas
o
m 1
.
ThepresentlywidespreadgyrocompassStandard‐
20 is said to have a manufacturer’s error [7] for
speeds of 70 knots atlatitudes up to 70
0
not higher
than
sec4,0
0
. An improved performance
tracking system (75
0
/s) allows to reduce random
errors of radar direction finding systems ARPA in
stormyweather.
Thegyrocompassusesmicroprocessortechnology
based on mathematical models in the form of
differential equations. The microprocessor performs
a calculation and compensation of speed deviation,
aswellasinertialdeviationsthatoccurwhenaltering
courseorspeed.Thesameorhigherstandards[6]are
metbynewgyrocompasses:SR‐180MK1,Gyrosta
r‐2,
ГКУ‐5,Meridian.ThebasesystemGMisbuiltonthe
solutionof gyrocompassSR‐180 MK1 and magnetic
compass.Itisdecelerated,thatthisthesystem[6]has
themeantimebetweenfailure40,000hours.
The reliabilit
y and readiness of GPS and
GLONASSsystemsissohighthatitdoesnotcause
interruptions. Breaks in their operation are so short
andrarethattheydonothaveasignificantimpacton
theoperationofthevessel.
Modern gyrocompasses, even those with
electronic and computer components, are not the
most reliable navigation devices. A survey of 212
skippersshowedtha
teachofthematleastoncewas
returning to port using only a magnetic compass
whilethegyrocompasswasbroken.
The magnetic compass is a highly reliable and
cheap indicator of shipʹs course. It is a very good
solutiontotheproblemofgyrocompassmonitoring
andit
sback‐updevice.
4 CONTROLANDBACKUPFUNCTIONSOF
MODERNMAGNETICCOMPASS
Thecontroloftechnicalconditionandaccuracyofa
gyrocompasscanbedonebycomparingthecourses
from two gyros, but such redundancy is expensive
and relies on power supply. A combinat
ion of a
gyrocompass and a magnetic compass much more
effectively and in all circumstances guarantees that
thedestinationwillbereachedinduetime.Statistics
showthatthemeantimebetweenfailures(MTBF)of
todayʹsgyrocompassis3000÷4000hoursandforthis
reasonthequest
ionofredundancyistopical.
Positiveindicatorsofqualitygyro‐andmagnetic
compasses are shown in Table 1 in green and the
negative indicators are in red. The gyrocompass +
magnetic compass set allows to combine good
indicatorsofthetwocompasses.
High precision of the gyrocompass is used in
regular situations, while high reliabilit
y and
autonomyofthemagneticcompasscometothefore
incaseofgyrocompassfailure.
Table1.Mainindicatorsofthequalityofmoderngyroand
magneticcompasses
_______________________________________________
IndicatorsViewofcompass
ofcompassquality Gyrocompass Magneticcompass
_______________________________________________
1. Accuracy[0] 0.5
0
÷0.8
0
1.2
0
to1.3
0
2. Reliability[h] 3000÷4000 Nostatistics
3. Theautonomy Online Offline
4. Thevalue[$] 20,000‐40,000 2.000‐3.000
5. Requirementsto Service Theannual
servicerules compensationof
deviation
_______________________________________________
Todaythema
gneticcompassandgyroareusually
combined within an integrated navigation system,
allowing to maximize the advantages of either
device, bypassing their shortcomings. In such
systems, comparison of data is carried out
automatically.Thesoundandlightsignalsinformthe
user about a difference of true courses from the
permissibleva
lue.
An example of such system is Naviwarn from
Plath.Thesystemʹswarningbeepcanbeimmediately
shutoffandthesignallightturnsoff automatically
once the fault is corrected. The system Naviwarn,
based on the gyrocompass Navigat‐X, can use the
magnetic compass Jupiter, Mars and Neptun. Such
systemisthesameinthe gyrocompass Standard‐20.
Naviwarn Gyroma
gnetic sets and systems are
typically found on high‐end vessels or navy ships,
whiletherankandfileseafarersusuallydonothave
opportunitiestousesuchsystems.
Both functions of a magnetic compass (control
and backup) are essential in terms of ensuring the
541
safety of navigation and of economy. To properly
securethebackupfunction,regulatoryrequirements
for the annual compensation of the magnetic
compass deviation were established in the previous
century. The accuracy requirements for deviation
were established at the level of ± 3
0
for the master
compass and ± 5
0
for a steering compass. In those
days, the magnetic compass was not qualified as a
spareindicatorofthecourseandsuchhighdemands
wereunderstandable.
Although the current status of the magnetic
compassonboardhasfallen,asitisnowregardedas
areservecompass,therequirementshave
remained.
The time and cost of compass adjustment are
quitesubstantial,especiallyforlarge‐tonnagevessels.
Compassadjustmentmustbeexecutedeveryyear.It
is appropriate to take a look at the effectiveness of
relevant requirements and costs under the new
conditions.
5 ANALYSISOFTHECOSTEFFECTIVENESSOF
DEVIATIONADJUSTMENT
Modern satellite systems have increased the
reliability of navigation and, as a consequence, the
role of magnetic compass has decreased. In this
context, it becomes relevant to ask how costs
associatedwithamagneticcompasscanbelowered.
Aboveall,itisnecessarytoreducethetimespenton
the
determinationofdeviation.
According to the requirements of classification
societies the table of deviation is legitimate during
oneyearafterdeviationadjustment.However,while
navigating in ice or in stormy conditions the
deviation can change after a few days of sailing. A
one‐yeartermdoesnotguaranteecompassaccuracy
in
allcircumstances.
Thereducedroleandimportanceofthemagnetic
compassinadvertentlyreflectsitsuseon vessels.At
thesametime,theregulationsdonotprovideforany
exemptions to quality of service of magnetic
compasses, including the quality of deviation
adjustment.
It is known that if high cost of
service does not
increase efficiency, people tend to avoid such costs
byhookorbycrook.Thisiswhatishappeningnow
in the global fleet in reference to deviation
compensation. Pleskacz in his study based on
observationsof35vesselsfrom17countries around
theworldshowsthatthespread
ofdeviationinthe
table today is characterized by a
0
8,4
m
. This
clearlyshowshowthesystemhaddegraded.
Navigators have technical skills and theoretical
knowledge to compensate the deviation by
themselves, but in most cases and most fleets they
have not been accustomed to do that and prefer to
pay, out of ship owner’s pocket. The navigator’s
passive attitude towards
the control and
compensationofdeviationwillpersistuntilasimple
method is developed that does not require
substantial time, special knowledge, skills and
qualifications.
6 ANALYSISOFTHECURRENTSTATEOFTHE
DEVIATIONPROBLEM
It has long been known that the vast majority of
vessels(symmetricalvessels)havethe
coefficientsof
deviation
A and
E
that practically do not exceed
0
6,0 andareverystable[1,2,4].
Uncompensated coefficient
D
in newly‐built
vessels is always positive and within 3
0
÷ 5
0
. It also
hasaveryhighstability.Afterthefirstcorrectionof
factor (D) by means of soft magnetic iron balls or
plates it is commensurate with the coefficients
A
and
E
(lessthan0.6
0
).
As a rule, at annual compensation of deviation
onlytheleaststablefactorsofdeviation
B
and C
arecompensated.Aftertheircompensation,thereare
measurements of deviation on eight courses and
recalculationoftheentiretableofdeviation.
Modern methods of deviation compensation are
performedinaccordancetocomplexalgorithmsthat
do not permit any variations or allow for specific
circumstances.
In fact, vessels with more or
less the same
coefficients A, D and E are operated without any
compensationyearafteryear.
ItturnsoutthattheannualcoefficientsA,EandD
havelowvalueandhighstability.
IfthecoefficientsBandCdonotcompensateup
to zero, and restore their values from the
existing
tables, you create a situation in which there is no
need to calculate a new table of deviation. with
restoredcoefficientsBandCandconstantcoefficients
A, E and D we “return to the previous table of
deviation.Itcanbesignedagainandprovidedwitha
new
datetobeusedagain.
Therefore, when you restore the old table of
deviation,allworkcanbesummarizedontwomain
compass courses (e.g. N and E) instead of twelve
courses of typical adjustment. The number of
required courses is reduced six times. This gain is
veryimportant,especiallywhen
youkeepinmindit
can be executed by a gyrocompass without
deviationspolygon.Inthissituation,thereisnoneed
to process measurement data and calculate a new
tableofdeviation.
The old table of deviation therefore can be
extended for the next period. Instead of one and a
halfhoursandcostsofproceedingtothetestseaarea
andback,itisbetterspend10
15minutesoftime
withnoneedforcalculations.
7 RESTORATIONOFTHEDEVIATIONTABLE
If the gyrocompass correction does not exceed half
degree,asitoftenhappensonmodernvessels,itcan
be rounded off and regarded as zero. In this case,
the gyrocompasscourse(GC)canbe set to
the true
courseTCorotherwise:
CECCdCCGC +=++=
(1)
542
where:
CC‐compasscoursefrommagneticcompass;
d‐variation;
δ‐thetablevalueofdeviationofmagneticcompass;
CE‐thecompasserror.
ThecoefficientCofmagneticcompassdeviationis
compensated at the compass course CC=0
0
. At the
samecompasscoursethegyrocompasscourseofthe
vesselisequaltothecorrectionofmagneticcompass:
GC=CE (2)
IfonthecompasscourseCC=0
0
theconditions(2)
are satisfied, the deviation δ corresponds exactly to
thetabularva lueandanycorrectionofthecompass
is not required. Otherwise, going on the same
compass course CC=0
0
, a regulator C(diametrical
magnet‐compensator) is setting the new value of
deviation δ according to condition (2). Under this
condition,thegyrocompasscourseGCisequaltoCE.
ThecoefficientCisrestored.
Similarly,atthecompasscourseCC=90
0
thefactor
B can be compensated. At this compass course the
gyrocompasscourseisequalto:
GC=90
0
+CE (3)
IfforthecompasscourseCC=90
0
theconditions
(3) are fulfilled, adjustment is not required.
Otherwise, going on the same compass course
CC=90
0
, regulator B (longitudinal magnet‐
compensator)issettingthenewvalueofdeviationδ
sothat(3)issatisfied.ThecoefficientBisrestored.
Toperformtheseoperations,youshouldclosethe
binnacle,providetheoldtableofdeviationwiththe
newdateandsignature.
Absolutely the same procedure for updating the
table of deviation may be performed on any one of
combinations of compass courses: (N‐E), (N‐W), (S‐
E),(S‐W).
Panels of modern magnetic compasses MK‐115,
MK‐145 include regulators (F
ig.1) of semi‐circle
deviationcoefficientsBandC.
The mean error
m
recovery of deviation to the
tablevalueisdeterminedbytheformula:
222
++=
dCCGC
mmmm
(4)
where
m
GC‐ meanerrorofgyrocompass;
m
CC‐ meanerrorofobservationofcompasscourse;
m
d‐ meanerrorofdeclination.
Whenusingthismethod,youshouldavoidareas
ofmagneticanomalies.
This simplified procedure for restoring the
coefficients of deviation B and C resembles the
computeroptionʺSystemRestoreʺ.
Figure1. The top of magnetic compass KM‐145. 1.
potentiometer, 2. vertical soft iron, 3. scale of revolving
roundverticalaxis,4.compensatorsofcoefficientD,5.cap
of compass, 6. regulator of coefficients B, C and vertical
forceZ.
This option is very often helpful to users of
personalcomputers,allowingthemtoregainthelost
elements of the Windows system, by the periodic
automaticrecordsofsystemsettings.
Asimplifiedmethodtorestoretherelevanceofan
obsolete table of deviation may be used for a
relatively long time
(10 years or longer), if no
significantstructure‐borneironreplacement,andthe
replacementofenginestakesplaceinthemeantime.
Such an approach will help reconcile the cost of
maintaining the effectiveness of the magnetic
compass and its impact, both in terms of economy
andsafetyofnavigation.
Shipsʹ
navigational service performs a control
magnetic compass deviation, and if necessary,
restores the table of deviation. If the alteration of
deviation is substantial (due to major repairs,
reconstruction of the ship), shipʹs technical service
mustorderacompassadjusteronboardoftheship.
Itisclearthattheintroduction
ofsuchasystemof
deviation compensation must be legalized by the
relevant legal instruments adopted at the national
andinternationallevel.
ItisinterestingthatmodernʺRulesonConvention
Equipment ofthe Shipsʺ [5] has a notation that
“The Register does not oversee the timeliness and
quality of the
identification and destruction of
deviationofmagneticcompasses.”Itfollowsthatthe
deviation of a magnetic compass is the problem of
theship.
The issue of accuracy standards for deviation
compensation is also very important. Traditional
requirements for the accuracy of deviation
compensation were established in the 20th century.
For the
master magnetic compass [5] the maximum
valueofdeviationafteritscompensation wassetto
be ±3
0
. The value of deviation for steering compass
shall not exceed ± 5
0
. These demands were
understandableandreasonableforthosetimeswhen
therewasnosatellitenavigationandtheroleof the
magneticcompasswasmorevital.
Satellitenavigation has increased very much the
safety of navigation. The master always has high‐
precisioncoordinates,controlsthe movement of the
vessel, and the
accuracy requirements of the
543
magneticcompassnolongerplaytheformerrole.It
has preservedremaineditsbackup role (tobe used
justincase).
During satellite navigation, even if the magnetic
compass is not very accurate, there is always a
possibilityofusingtwopointsfromGPSandgetting
a reasonably accurate ground
track angle. In
emergencyconditions(failureofgyrocompass)when
theGPSisinoperation,therequirementisratherfor
magnetic compass stability, reliability being less
crucial.
Being aware of this fact allows not to meet the
strict and expensive standard for compensation of
deviation of the main compass (± 3
0
). In the new
circumstances, it is sufficient to maintain the same
levelasforthesteeringcompass(±5
0
).
Experimentalverificationoftheproposedmethod
wascarriedoutatthedeviascope,inthepremisesof
Szczecin Maritime University. The results are
presentedinTable1.
Originally, the compensated deviation is
presented on eight courses in the first column. The
coefficientsofdeviationA,B,C,D,Earegiven
atthe
bottomofthiscolumn.
Uncompensateddeviationunderthenewposition
of deviation magnets and its coefficients are
presentedinthesecondcolumnofthetable.
The restored deviation and its coefficients are
presentedinthethirdcolumnofthetable.
Table 2. Return of the table of deviation on the compass
coursesNandS.
_______________________________________________
Compensated Uncompensated Restored
deviation deviationdeviation
_______________________________________________
MK
0
KK
0
Δ
0
MK
0
KK
0
Δ
0
MK
0
KK
0
Δ
0
0 0.5‐0.5 0 2.5‐2.5 0 0.5‐0.5
45 43.5 1.5 45 48‐3.0 45 43.25 1.75
90 89.5 0.5 90 93‐3.0 90 89.5 0.5
135 134.50.5 135 136 ‐1.0 135 134 1.0
180 179.50.5 180 177.5 2.5180 179.5 0.5
225 224 1.0 225 220.5
4.5225 225 0.0
270 270 0.0 270 267 3.0270 270.7 ‐0.75
315 315.5‐0.5 315 314.5 0.5315 316.5 ‐1.25
_______________________________________________
A=+0.4
0
A =+0.1
0
A =+0.2
0
B=+0.4
0
B=−3.1
0
B=+1.0
0
C=−0.3
0
C=−1.8
0
C=−0.2
0
D=+0.6
0
D=+0.5
0
D=+0.5
0
E=−0.1
0
E=±0.0
0
E=+0.1
0
_______________________________________________
Comparison of the coefficientsA, B, C, D, E in
the first and third columns indicates that the
coefficientB isrestoredtowithin0.6
0
.Theaccuracy
ofreproductionofthe remainingfourcoefficientsis
atthelevel±0.2
0
.Sucharesultcouldbedescribedas
excellent.
Inrealconditionstheerrorofrestoringdeviation
willbesubstantiallyhigher.Thereasonsfor this, as
canbeseenfromtheformula(4)isthetotalerrorof
gyrocompass
GC
m
andofmagneticdeclination
d
m
.
Today it can be equal to not more than one degree
0
0,1
ГК
m
and
0
0,1
d
m
. The mean error of
observation compass course from a magnetic
compass can be taken as
0
5,0
CC
m . The mean
error of deviation recovery under this condition is
0
5,1
m
.Thisresultcanbeconsideredasgood.
8 CONCLUSION
1 Regulations of classification societies concerning
annualdeviationcompensationareobsolete.They
do not pay off and unnecessarily burden ship
owners and seafarers. In the era of satellite
navigation the requirement of annual deviation
compensationtotheaccuracylevelof3
0
mustbe
reformulated.
2 Thehereinproposedmethodofupdatingatable
of deviation using the gyrocompass allows to
compensate the deviation quickly and simply in
anysituation.
3 The easy‐to‐use and affordable method
guarantees the achievement of a positive result
andprovidessaveslaborinreferencetodeviation
compensationwork.
LITERATURE
M. Jurdziński. Dewiacja i kompensacja morskich
kompasów magnetycznych. Gdynia, Wyższa Szkoła
Morska.2000r.182s.
Е.М. Lusznikow, R.K. Dzikowski. Dewiacja kompasu
magnetycznego. Szczecin, Wydawnictwo Naukowe
AkademiiMorskiej.2012.104s.
Е.М. Lushnikov. Deviation of magnetic compass. USA.
Arizona.2010.122p.
V.P. Kozuchov, V.V. Voronov, V.V. Grigoriev. Magnetic
compass.Moskov,Transport.1981.214p.
Regulations by conventional equipment of sea ships.
Leningrad,“Transport”1981.272p.
Е.L. Smirnov. Marine navigation technique. Sanct‐
Petersburg,ELMOR.2002.224p.
Е.L. Smirnov,А.V. Jalowenko, V.К. Perfiliev, V.V.
Voronov, V.V. Sizov. The technical means of
navigation.Sanct‐Petersburg,ELMOR.2000.648p.
