MARINE DEPARTMENT,NEW ZEALAND. GRAPHIC METHOD, OF EXHIBITING THE DIRECTION AND AMOUNT OF THE DEVIATIONS OF SHIPS'COMPASSES

General Remarks. mmmMPmm th. renvult should' b. recordrf „„ For„ j3 are flYd"*""examml.., wj.h th. actual result, obtained in swinging™. "IhTriri "an" the " Jane respectively, for compaa. .lamination.) " un " »° d Explanation of the Diagram p=.o^frs. d '!n:cot„tn- *.. dS?," 'V.Jmeram; wuile the dotted lines, which are to represent oTtne" d,.°g r r™. """ , "■"'"" °" d ° f "» ""»'. » """-ft- the or .a 4" Wm "*" bT bxspeotion, the oontinuon. lines and the dotted lines of the same.nam, interaect on th. c.ntr. lin., or "lin. of no d.,SiioT" but owing to the inclination of the lines, any deviation of four p" Z'or less, anther to the east or west can be ranmu.W o. ... a:.~ ~ v .? intentions of th. continuous auTdotteoS.. " "» "" To draw the Deviation Curve. ....^i? ml r■.T M *^k.- 0,, the .■^■e™ l b y a penoil cross the point of intersection! of the oontinuou. line representing any point (or fr«tiou) of a correct magnetic compass and the dotted line representing the oorreJfoSfrS Tn'b'" t ? Mi "" ■ hi ■ , ■• °w» compa". «iund?"th, Keco„a of Obe.rvat.oru," (Form Aor B). Bepeet thi. process for ™S BfS ° b .t_!' >d ' "a™ ,b i? n *b 'b« «ro«« so .narked draw .panel, !3r ,". ,t *"? J*" 4 ' I 1? ' ,n ™ ,, "booJti be inked in when Kal°j adjusted to the satisfaction of the operator ""any It ahould be noted that when tne veaael ha. be.n .wung to th. poinU of a correct compass, „ d th. result, recorded in the Form A Jl the »"«•—» «»" „f . eorrrei corapua,; and all fractional readmgs mu.t be on (or b.tV.™ if the oard hsss been read to Bths) the dotted line.. ™w,«t v tne . . Wlhen, however, the results have been recorded in the Form B all the interactions must be on the thiol, dolled Ii„„ reprinting ,c£i. of the c0n,,»="»..." d "" *"*"~» -** °»" f be on erU„»e Z .. . t^^^o?*"" T o oonatrnct the curve for the binnacle oompaas of the r>rnr!ih" (, IV U " D i. Br T N , 0 'v l), . Tr "" , b««bickcontfo„ou.li;,fr„„ Kortlh on the right side of the diagram downward, tow.rd. th. left and trrae. the dottiS line from H.J«. on the left side of the dtgraru' which"ark "" P °'" t ° f ">"»•«*»>« hi tSaud. Traace the thick continuous line from N. by E. on the right of the ™XT Jo-Pward. toward, the l.ft. and th. .lotted lin. from if. by E.Jis on the Heft of the diagram downward, toward, th, right, till their inter, section is found; mark as before, and so on Wbhen a reading i. given to Sths, the intersection will fall half-way ™ m."*" of 'blotted line,. The., in oon.truoting the •" huriri" J v^S"' 1 . fe m " d ? °" ,h " oontinuon. lin. repre.entiug correct mag. N.K. by H. fcattwta, between the dotted line representing nSn^a.,.7"*b",N 7 H -*"' ""' "» iMM "» "presenting ship! e»ily bJeiiKy 1 "" "'*""" M "°° »' «"° ''«• — Uses of the Curve. to iftSlvlrf™ ."° id complication, uo aUu.ion h» been mad. at , ,? i** ,boT " ojrection, for drawing the curve , when the reasel .""own"'„"„ d ,± W ''' t d " i " i °°» '?' • correct ...pa, „ r fo, the vessel , own compass can be measured from the diagrarS with ample 52' " ,d "">" *~*e«. aecert.in.d with crt.iai, by simple C shin^ I "™™.''.* 1 " 0 *","» ble 'o' S»*ug the corre.ponding correct and ac uallTteste? TSn'.S' ""'"Z' fr "' i °° " hioh h " "* b ~n S JZ ,,'!'?. „ i„" "" over, g„. . good approximation to the deviation, and couir.es at any part of the oard from observation, on a comparatively em.ll n.nmber of points. Should, however, th. ye.,,1 not be,»one to every p.oint, ,t „ eeeentid that th. N.E, 8 S., B.W , and N W po°X It SnL™."nS"n'i*°„ U , ld ,.c c , »"■ 'th.cc, S. P ..'X°J cour^=h^^ d . b if y n,2. U rr,or;T.Sr;r k, '" "" ob ""* U °™ Examples. X. To fflnd the deviation for any point. RUILE— On the dotted line representing the point if it be a shin', compel, point, or if it b, a correct compu. point on the continuousSe meuure, the distance from the intersection ofth. curve to Centre hi whM ,il. ih^""' o ,' V""' 1 ' ~ t ° nt "» »™ber of on. «,.p„°n, , S which errc, th, given line between the centre line and the curvi (makiuu attowaucM, for any fraction), mdthe sum »IU be the d™.tion-S»r ? tf th. curve be to th.r(e«< of the e.ntr. line, „,„„',, SUtfl ,b.|pLVk-Kn l {eo h rr,t.t^V h '^^^^^ Zl^,ZotL^4i.>E (b '° m ' """ ofth. centre line , Inn n.-Wbat is th. dsviation of the " Ahuriri'a •■■ comnass when sh. ..hewing N.E. 4, Wow,, cc™,o,,f compus ,h. d„.. j r"" ,h * c""? i" on the right of the centre line, and it intersects £ E clrr™? ™P'«"»'">» "* on the ship's comp„. oi th. line o'Te 1 point B "Wtei. or one point from the centre. The answer is im^^'•"" W^o.^^'T Sx quarter,)| from th. centre line. Th. answer con«,,ie„tly I, fjjoin'tw ing rSrf~" T ''" P ° i °" """* '""""' U"" ou " e "" a >"W oorr«rpondfor the"™lVo !X;~ a °PPO" —>J »™ry eecond point to have been observed No 21 „ 0 ? mi "S". <V'v 'be Point, lettered to the left of Di.gran. -™. cornS ?""* "' "" "" * "" "™ ~»5-. th. S'.!.b^„7.a i °'"™;•°' , dotted line of E. by N. Jth, of a point to the Boutbh of the continnou, line of Eaat i the an.wer therefore i, E |S •h. «yz. •" b.7te.7,7f t0 """' ""■• w - 00 ""' m >*"> a °' h ™ »»" ..■ T h h .". o "'"*.l°'T eot i t .b"oontrnuousline of W. correct mermetic half. r,tT.""'N*|» "°' W ' b) ' "' ""' W '"'W.. •ootb. answer •w'°*™ l °" wbiob i« th. .am. a. Form A but diff.rently he.ded, is the SS™f-™°V" """■ *" d ro "° D " lh « ticriation oafd used in New *"""?' A » "°* r "" »" usually taken from a chart on which correct magnrtm eeereee are ,hown, it „ convenient to have correct magnetic courees nn the first column of the Bteering Table; but inasmuch as 'hi-!™,; are ..ldorn need except to correct th. observed bearing, of :fa.,v,"t?o™ p T e .b'£. h,re "" "*'' "~ ""•""• ~»~ " "» «« ~ S ™ r,coSio ?m i. th F , ~a h ".a be ™."' n ; nB * 0O "~' "«P- •»» «■. result. ™Siil li A ! "" •t.'cr.ng-cour.e card i, a simple oopy of the Jtf °SS"■"!■»• (*?T omitted ooiut. being «U,d in with the Hd of the curve). tWhen she ha, been heeler! to the point, of her own eompa,., and St.Tr? re °S d ' d ° n F -°™ B . 'b« -bole ofth, steering con™ m„.7 he taken ffrom the curve in the manner of Example V When, the observation, have been recorded in th. Form A, the hjThafT ™*»» <"•<»,'•; ,f"" d °P "I meunrement from th. digram n th. nunnner of Example 111. When the Form Bi. adopted, th, de.ieruvria "*.. J B °'i r S d ', reo . U J'. but there is much leas Vi.k of error in noting the, direction of the deviation if the diagram is used. Obaenrve. -The Deviation Table, Form D, i. alwao, to be filled up from meaeiurement, on the dotUdlin.t, aa in Example Hi: d«i l i r ° te, .;~ l , n °J"foting bearings of objects for deviation, it is the deviation , due to in, direction of the ve„el , be.d which must be applied, ao. the dewiation corresponding to the actual hearing Marimer, should consequently observe that it Is a.nlial to note the direction oftli. „ th , ti m, that the bearing of any object i, taken, audi both should be recorded in the log.