International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 4

Number 1

March 2010

65

1 INTRODUCTION

According to requirements of Register the table of

deviation is legitimate during 1 year after compensa-

tion of deviation, however, at navigation in ice or in

storm conditions it can be not actual already after

some days of navigation. It cannot be guarantee for

high accuracy compass during one e\year at all con-

ditions.

The role of a magnetic compass at the modern

vessel today is reserving of navigation. This role of

magnetic compass is explained by means of high ac-

curacy of gyrocompass and high accuracy of GPS

receiver. Such decrease in a role of a magnetic com-

pass is involuntarily reflected in carefulness of his

service.

At the same time, normative documents do not

provide any indulgence to quality of the mainte-

nance and service of compasses, including to quality

of deviations service.

It is known, that if expensive services do not raise

efficiency of works them try to avoid by every way.

It now occurs on fleet regarding carrying out devia-

tion's works, that, certainly, does not promote a safe-

ty of navigation.

Today the navigator has such technical and theo-

retical base, that he can possibility to provide carry-

ing out the deviation's works itself, but he is not ac-

customed to this during all history of fleet

development. He prefers to pay, especially not from

the pocket.

The passive relation of the navigator to monitor-

ing and compensation of deviation is explained by

the complication of contemporary methods. It is

necessary for stimulation of navigator to monitoring

of compass the new effective and simple methods

which are not demanding essential time expenses.

2 THE ANALYSIS OF DEVIATION'S FACTORS

AT CONTEMPORARY SHIPS

The analysis of stability of deviation's factors [2]

shows, that factors

A

and

E

for contemporary ves-

sels practically do not exceed

0

6,0

and are very sta-

ble. Not compensated factor

D

for new building

ship always is positive and is in limits

00

53 ÷

. The

factor

D

is high stability.

As a rule, at annual compensation of deviation

only the least stable factors of deviation

B

and

C

is

compensated and under compensation the table of

deviation is anew recalculated entirely.

The modern methods of deviation's works are

carried out usually according to the hard algorithms

which are not admitting any variations and the ac-

count of concrete circumstances.

Actually on the vessel at practically constant fac-

tors A,

D

and Е from year to year are anew deter-

mined all factors of deviation and the table of devia-

tion is recalculated. It happens even so, that factors

again accepted to the account A,

D

and Е have ac-

curacy below, than it was in the old table. It is ex-

plained, first of all, that values of these factors are

commensurable with a margin error their calcula-

tions.

It turns out so, that annual determinations of fac-

tors A, Е and

D

at their small value and high stabil-

ity it is inefficient expenditure of time and resources.

At typical procedural deviation's works the fac-

tors B and C of half circle deviation are compen-

sated. Obviously, it is necessary to use elastic algo-

rithms for counting these changes.

The Problem of Magnetic Compass Deviation

at Contemporary Conditions

E.M. Lushnikov

Maritime University of Szczecin, Szczecin, Poland

ABSTRACT: The problem of accuracy magnetic compass for contemporary condition is described. The tech-

nique of actualization of deviation’s table at conditions of voyage is offered. The methods and means of actu-

alisation is described also.

66

At such state there is a question about expediency

of compensation of factor B and factor C up to zero.

If the factor B and C to return to former tabulated

values position, that there is not necessity of recalcu-

lation of deviation's table anew.

3 THE ACTUALISATION OF DEVIATION'S

TABLE AT CONDITION OF VOUAGE

At the same circumstances all deviation's work can

be executed for example at the course N and E, in-

stead of twelve courses as it take place at typical

procedural works. Thus, the time of manoeuvres can

be reduced in 6 times. This prize is rather essential.

In addition from process of deviation’s works it is

excluded the cultivation of measuring information

and calculation of the new table of deviation. The

old table of deviation is prolonged for new term. In-

stead of one and a half hours of time without taking

into account expenses for transition up to special

aquatory and back it is enough to spend 10

÷

15

minutes of time without any calculations.

The sequence of operations is according to:

– The deviation of magnetic compass is determi-

nated at the compass course

0

0

. If the value of

deviation is differed from tabulated value less

than

0

5,0

it is not necessity of correction. If the

different of deviation is more than

0

5,0

it is nec-

essary to recover the value of deviation from the

table.

– The deviation of magnetic compass is determi-

nated at the compass course

0

90

. If the value of

deviation is differed from tabulated value less

than

0

5,0

it is not necessity of correction. If the

different of deviation is more than

0

5,0

it is nec-

essary to recover the value of deviation from the

table.

– The time of correction must be written at the ta-

ble. The signature of executor must be at the ta-

ble also.

Such simplified way for correction of half circle

deviation demands enough solid data about magnetic

declination. From this reason the choice of a place

for carrying out of such works it is necessary to

avoid areas of magnetic anomalies, etc.

4 THE REQUIREMENT OF ACCURACY AT

ACTUALISATION OF A TABLE

The deviation of a magnetic compass is determined

from one of a formulas:

VCCTCD −−=

VCBTBD −−=

From these formulas it is visible, that accuracy of

determination of deviation and also accuracy of res-

toration of its former value depends, first of all, from

accuracy of knowledge

TC

or

TB

and from accura-

cy of values of variation

V

. The standard error of

restoration of deviation up to its tabulared value is

determined accordingly on one of formulas:

2

V

2

CB

2

TBD

2

V

2

CC

2

TCD

mmmm

mmmm

++=

++=

Such simplified procedure of deviation’s works

reminds inherently a computer option ”restoration of

system”. This option very much frequently helps us-

ers of personal computers, allowing to return the lost

elements of system " Windows ", due to periodic au-

tomatic records of installations of system.

If to carry out this analogy, that the values of de-

viations on the course

N

and

E

represents the writ-

ten down(at the table) values of deviations. This val-

ue is nominative to restoration.

Comprehension of such fact allows the navigator

widely using a computer in the daily practice, to find

for an offered method a corresponding place in uni-

form philosophy of maintenance of navigating safety

of navigation.

5 CONCLUSION

Such simplified method of restoration of a urgency

of the out-of-date table of deviation can be made

within 4

÷

5 years if not it was made significant re-

pair work.

Such statement of a question will allow to har-

monize expenses for maintenance of efficiency of a

magnetic compass and feedback from its party, both

in aspect economic, and in aspect of safety of navi-

gation.

LITERATURE

Jurdzinski M. Dewiacja i kompensacja morskich kompasów

magnetycznych. Gdynia WSM 2000, 182 str.

Воронов В.В., Григорьев Н.Н., Яловенко А.В. Магнитные

компасы. СПб.: Элмор, 2004. 191с.

Кожухов В.П., Воронов В.В., Григорьев В.В. Магнитные

компасы – М.: Транспорт, 1981. 212с.

.