Compensation of Magnetic Compass Deviation at Single Any Course

Transcription

1 International Journal on Marine Navigation and Safety of Sea Transportation Volue 5 Nuber 3 Septeber 0 Copensation of Magnetic Copass Deviation at Single Any Course E.M. Lushniov Szczecin Maritie Acadey, Poland ABSTRACT: The new ethod for copensation of deviation of agnetic copass at one any course is offered. The theoretical substantiation of a ethod is given, the analysis of accuracy is ade, corresponding conclusions and recoendations are ade. It allows to carry out a deviation s wors without interruption fro voyage. INTRODUCTION. The copensation of deviation of agnetic copass is usually carried out on the special aquatory equipped by leading line. The priary copensation of deviation is executed at an output of a vessel fro building shipyard. All factors of deviation is deterined and copensated in this case. The deterination of residual deviation and calculation of the table is ade after copensation of deviation. Such procedure can deand soe hours of tie. At annual deviation's wors the copensation of the ost inconstant factors of deviations B and C is ade only. These factors on new building vessels can reach values They are the ost instable in stor conditions, at ice navigation, at noc about a quay on ooring, etc. As a rule, the table of deviation guarantees high reliability of the data up to the first heavy stor. The ost often used ethod for copensation of factors B and C is the ethod of Airy, which is carried out at ain agnetic courses. Accuracy of copensation depends on accuracy of supervision, on accuracy of operations by agnets - copensators, on hysteresis effects in the body of the vessel at aneuvering by eans of course. After copensation of deviation the definition of residual deviation and calculation of the table is carried out. Especially any probles are delivered at deviations aneuvers to large-capacity ships such as supertaner, big passenger ship, the big ilitary ships and subarines etc. Every tie even the inial progra of deviation's wor is connected to loss of operational tie and an additional overhead charge. The proble of navigational safety is included in this case into the contradiction with econoic probles. The radical decision of this question would be possible at presence of a ethod for destruction of deviation without derivation of a vessel fro the basic wor. Such stateent of a question is possible only at presence of a ethod for destruction of deviation on one any course. The deviation's wors at one course would allow as considerably to exclude influence of hysteresis effects on accuracy of deviation's wors. Thus, the way of destruction of deviation on one any course is the ost effective way to liquidate unproductive expenses of tie. TE DEVIATION OF MAGNETIC COMPASS AT CONTEMPORARY CONDITION. At conteporary ships of syetric design the constant factor of deviation A and the factor of deviation E depending fro asyetrical soft steel of the ship are in liits 0, 0 0,6 0 and are characterized by extreely high stability []. The factor of deviation D after copensation by the help of without induction s sheet of a soft iron [] does not exceed 0,5 0 and as differs very high stability. It can to tell, that the values of these three factors of deviation are situated at the sae level as accuracy of supervision of courses and bearing. owev- 303

2 er, according to rigid algorith of Airy, these factors without any need are deterined and recalculated anew for use in the new table of deviation [3]. All this operations can be qualified, as unproductive wors with loss of tie for easureents, processing and calculations. Exact expression for deviation of a agnetic copass is iplicit function fro copass course and enters the nae as: Sin Acos BSin CCos DSin( ) ECos( ) () d b P cz Q fz a e d b A ; B ; C ; D ; E thus: - a horizontal coponent of force of terrestrial agnetis; Z - a vertical coponent of force of terrestrial agnetis; P,Q - longitudinal and cross-section agnetic forces fro according hard ship's steel; a,b,c,d,e, f - paraeters of Poisson, describing constructions fro soft ship's steel; a e copass. - factor of shielding of a agnetic Paraeters of Poisson a, b, c, d, e, f and as factor, are functions of the sizes and fors of ship's soft steel, his reoteness fro a copass and agnetic characteristics of a case aterial. All these characteristics are constant constructive paraeters of a vessel, than high stability of factors A, D, E explains. Taing into consideration this circustance, factors of deviation A, D, E usually consider constant and at perforance of annual procedural wors these factors do not adjust. In this case the proble of annual deviation's wors is reduced to indenification of factors B and C and to calculation of the new table of deviation. Such operations at annual deviation's wors are the established practice already for a long tie. The last inistry's instruction of Russia Recoendations to navigation's service of 989 year do not define the tie of actuality for a table of deviation. Only the level of accuracy according to requireents of IMO is forulated at this instruction. At the sae tie Recoendations to navigation's service for a ships of a fishing fleet contains record about the axial year interval of actuality of the deviation s table. These departental distinctions ephasize coplexity and a urgency of this proble. Progress in developent of satellite systes of navigation and gyrocopasses has led to that agnetic copasses on sea vessels basically carry out reserving and onitoring function. Unproductive expenses of tie for deviation's wors stiulates a negative attitude of ship-owners and captains of ships. Modern aret conditions deand optiization of production and the proved tie expenses. It is natural, that such optiization should be ade in view of safety of navigation. 3 PRECONDITIONS TO DESTRUCTION OF DEVIATION WITOUT INTERRUPTION OF VOYAGE. If the factors of deviation A, D, E are sall and constant, there is no need to spend tie for deterination of these factors anew. It is necessary to tae into account their values fro the previous table. The sae logic can be continued further. Factors B and C at carrying out of deviation's wor can be not destroyed up to zero, and to restore their forer residual tabulated values []. Such step gives the basis to consider, that after restoration of factors B and C all factors of deviation correspond(eet) to values of the old table of deviation and to expect the new table there is no necessity. Validity of the forer table in this case can be prolonged for one year. All deviation's wors will be reduced in this case only to restoration of factors B and C without expenses of tie for 8 courses for deterination and calculation of all five factors. Also there is not necessity for calculation of new deviation's table. Such actualization of the forer table of deviation can be ade during 5 years. owever the deterination of factors B and C for the purpose of their return to forer tabulated values deands not less than two equations, that is, at least, two courses. Otherwise it eans, that copensation of two factors B and C at one course is ipossible. It is possible to notice, however, that in navigating practice exists essentially various two ways of deterination of deviation. The first way bases on use of navigating easureents. The second way bases on physical easureents of agnetic forces with the subsequent calculation on this basis of deviation's factors. Siultaneous use of these two essentially various ethods allows to receive the issing inforation for the deterination of a tas in view on destruction of two factors deviations B and C at one course. 30

3 DETERMINATION OF FACTORS B AND C AT ONE ANY COURSE. The set of navigating ways and eans for deterination of deviation of a agnetic copass on an any course of a vessel is nown. For this purpose it is possible to use a terrestrial leading line, celestial object, reote reference points, systes AIS and gyrocopasses. The deviation of a agnetic copass deterined by navigating way can be written down as iplicit function of copass course КК as expression. Taing into account, that in ters of set sizes are deviation (easured by navigating way), copass course КК, and as factors A, D and E (fro the previous table), the expressi0n can be copied to ore copact ind: В sin C cos () sin A cos Dsin( ) E cos( ) (3) Thus, the equation connects two unnown factors of deviation B and C by eans of easureent of deviation. As the second issing equation can be used equation of total ship's agnetically force of copass K. It is nown [], that the value of easured force K loos lie: K [cos Asin B cos C sin D cos( ) E sin( )] () Expression can be copied to ore copact ind: B cos C sin (5) where cos Asin Dcos( ) E sin( ) (6) Thus, the syste of two equations and 5 at two unnown factors B and C is received: Вsin C cos В cos C sin (7) The solution of this syste of the equations gives: B C sin cos cos sin (8) At essential changes of these factors they ust be restoring by eans of regulators B and C of copass before forer table's values. For restoration of forer values of factors B and C the value of correction and is calculated under forulas: B C Т Т B C (9) where B T and C T - values of factors B and C fro the table of deviation. If factors of correction and are positive, readout of each regulator increases before the corresponding value and on the contrary. Thus, joint application of navigating and physical easureents allows to solve a proble which all tie was considered insoluble. Both factors B and C depend fro correction a coponent and. Navigating coponent, apparently fro expression, depends on accuracy of definition of deviation and fro accuracy of tabulated factors A, D, E. Correction coponent, apparently fro expression 7, deands nowledge of exact values of resulting copass force, a horizontal coponent of terrestrial agnetis, factor, and as deviation and factors A, D, E. Except for accuracy of the navigating data the exact data of physical easureents here are required. Accuracy of attitude / can be provided with use of the sae deflector for easureents on coast and on a vessel. Accuracy of factor in usual circustances never represented special interest. In this case of accuracy of nowledge of this factor are deanded uch. The situation is facilitated by that it needs to be deterined accuracy once as his stability as is extreely high as stability of factors A, D, E. Believing, that deviations are characterized by rather sall angles, that usually corresponds to the validity, both settleent coponents and at high accuracy can be siplified to a ind: A D sin E cos D cos E sin (0) In view of these siplifications the correction and will becoe: В ( A E)sin D cos ( A E) cos D sin Final record of factor and can be subitted as: ( M )sin N cos ( U ) cos V sin () () 305

4 M A E; N D; U A E; V D. Factors M, N, U, V it is necessary to calculate at once after full indenification of deviation and calculation of the table of residual deviation. Forulas and value of factors M, N, U, V are used at the further annual procedural wors on copensation of deviations factors B and C. Substitution of these nuerical values in beforehand prepared forulas allows to calculate quicly values of correction's factors and and to enter the with the help of corresponding regulators. Application of such ethod directly at a cargo ooring, as a rule, is not expedient owing to presence on a ooring and in designs of a ooring of the big iron weights, and as positions of ship iron not in a arching way. The ethod is the ost expedient for applying at an output of a vessel fro port when it is situated on leading line. Such operation can be executed by deviator so as ship's navigator. For perforance of wors it is required no ore than 0 inutes. In this case disappears necessity of special aquatory and additional tie for deviation's wor. All this process can be naed as a process of restoration or process of actualization of the forer table of deviation. The ost iportant in all it is that this actualization can be ade on one any course without interruption of voyage. 5 TE ANALYSIS OF ACCURACY OF A METOD It is obvious, that accuracy of restoration of the table of deviation depends on accuracy of deterination of proof values and. They, in turn, depend on accuracy of easureent of deviation, fro accuracy of the inforation about tensions of agnetic fields K and, and as fro accuracy of factor. Regular error of actualization of deviation's table. For an estiation of a regular error of restoration of the table of deviation it is necessary to execute differentiation of expressions () therefore it turns out: d d d d cos d d d d cos sin (3) Believing, that easureent of force on coast and force K on a vessel was ade by eans of the sae deflector and by the sae observatory these easureents can be qualify as the sae accuracy. d d In this case expression (3) corresponds to a ind: ( ) d d d sin cos () ( ) d d d cos sin Apparently fro expression (), accuracy of restoration of the table of deviation depends on accuracy of a navigating coponent of easureents d, a technical coponent of easureents d, and also an inforation coponent d. For estiating calculations it is possible to count that Н K,. In view of told, for an estiation of accuracy as a first approxiation expression () can be siplified to a ind: d d cos (5) d cos d Fro this expression it is visible, that the ain factors of regular errors are accuracy of navigating supervision and accuracy of nowledge of factor. The regular error of deterination of deviation at leading line is extreely sall. In this connection the basic role belongs to a coponent depending on factor. For aintenance of accuracy at a level 0,5 0 relative error of factor should not exceed 0,8 %. Such requireent is high enough, but quite real. Deterination of factor is carried out by easureent of copass force on four ain and four interediate course's with the subsequent calculation under the forula: 8 8 The requireents of Register to accuracy of copensation of deviation is 3 0. The relative ethodical error of deterination of factor will be not worse, than 0, %. Such accuracy is ore than sufficient. Exact value of factor should be deterined at descent of a vessel to water. The inforation on factors A, D, E and as about factor it should be ept carefully on a vessel before the next coplex chec and copensation of deviation. At capital reconstruction of a vessel, replaceent of the engine these factors should be deterined anew. Casual errors of actualization of the table of deviation. Influence of casual errors of supervision and easureents is estiated by the help of standard error under the forula: 306

5 x x... X X X n x x n Using as function f expressions (), we shall receive standard errors of the proof data ΔB and ΔC as: sin cos cos sin (6) For estiated calculations it is possible to accept ; ;. At such assuptions of expression (6) becoe sipler to a ind: sin cos ( ) cos ( ) sin (7) Fro these expressions it is visible, that casual errors of copensation of factors B and C depend on relative errors of all three factors navigating, technical and inforation. At standard error of deviation at the level 0 0,5, at relative accuracy of agnetic forces at the level of % and at relative accuracy of factor also at the level of % a standard errors ΔB and ΔC is not lower 0. Schedule of standard errors B and for such initial data is subitted in figure. C Fig. The standard errors and depending fro copass course 0 at B C 0,5 and 0,0 Fro figure it is visible, that casual errors of restoration of factors B and C are in liits 0,5, The additional errors fro instability of factors A, D and E are sall, and stability of the is very high. Such accuracy of actualization of deviation's table is quite sufficient. Not always the innovation gives a prize without by-effects and additional expenses. This case just does not entail any additional questions and probles. 6 TE CONCLUSION The offered ethod for copensation of deviation of a agnetic copass on one any course of a vessel is essentially new ethod allowing to reduce a routine wor of a vessel, connected with financial expenses. The ethod differs exclusive siplicity. It can be applied by navigators in conditions of voyage. 3 For introduction of a ethod in practice of navigation it should find reflection in corresponding progra of educational institutions. TE LITERATURE. V.V. Voronov, N.N. Grigoriev., A.V. Jaloveno. Magnetically copass. Sant-Petersburg. ALMOR, 00.. Kozuchov V.P., Voronov V.V, Grigoriev N.N. Magnetically copass. Mosov.: Transport, E.M. Lushniov. Copensation of agnetic copass deviation at conteporary conditions. International scientific conference «Innovation in scientific and education 008» Kaliningrad, KGTU, E.M. Lushniov. The proble of agnetic copass deviation at conteporary condition. International Navigational Syposiu TRANSNAV 09. Gdynia, Maritie. University 009. p