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M. 21918/14.



[Crown Copyright Reserved.



ADMIRALTY



MANUAL OF NAVIGATION



1914.




I . O \ I ' < » \ :

PUBLISHED I'.Y Ills MAJESTY'S STATIONERY OFFICE

i M i»i- purchased through in. Booksellei or directly from
II. M. STATION!. i:Y OFFICE at the following addresses •
Imperial Hocse, Kikosway, Lob don, Vf.0.2, and 28, A) don - w

I'll KK STKKKT, M \N< III Ml I. - I. VNDR1 ■ CUKSC'ENl L'ARDIl I

III ROD :

i. POH 8i >K BY, I.'i i'.. M'.'.' STREET, Dl mi v.

L919.
Prict 6s Net,



The Lords Commissioners of the Admiralty have decided
that a Standard Work on Navigation is required for the
information and guidance of the Officers of His Majesty's
Fleet; for this purpose the " Admiralty Manual of Navigation "
has been compiled by Commander Henry E. F. Aylmer and
Naval Instructor John White, M.A., under the supervision
of the Director of Navigation.

The Manual is designed to supply the needs of Junior
Officers and also of Officers qualifying for the duties of Navi-
gating Officer, and is to be regarded as the Standard Work
on Navigational questions in His Majesty's Fleet.

By the publication of this Manual the following books
are superseded and may be destroyed : —

Notes bearing on the Navigation of H.M. Ships.

Handbook of Pilotage.

By Command of Their Lordships,




Admiralty, S.W.

December 101 I.



10 610$ \\ i I I iIn 13 7000 l 10



11



PREFACE.

The Admiralty Manual of Navigation consists of four
parts : —

Part I. deals with the rhumb line and the position line, as
well as with finding the error of the chronometer and
the times of rising and setting of heavenly bodies ;

Part II. deals with pilotage;

Part III. deals with the movements of the atmosphere and
ocean ;

Part IV. gives descriptions of the various navigational
instruments, and explains how their errors are eliminated
or allowed for.

Thanks are due to —

The Astronomer Royal,

The Director of the Meteorological Office, for their
valuable assistance,

and to

W. G. Perrin, Esq.,

for reading the proofs of the book. The method of keeping
the reckoning during manoeuvres is the work of Lieutenant -
Commander L. H. Shore, R.N.

Figs. 262 and 263 have been reproduced from ' Les
Nouvelles Methodes de Navigation " by A. Ledieu, and the
permission which has been granted by —

Mr. Elliot Stock to reproduce Fig. 153,
Messrs. Elliott Bros, to reproduce Figs. 240, 251, 252, 253,
The Sperry Gyroscope Co. to reproduce Figs. 247, 248,
Messrs. Cary, Porter & Co. ,, ,, Fig. 256,

is gratefully acknowledged.

The following books have been consulted : —

American Practical Navi- Nathaniel Bowditch, LL.D.

gator.

Cours de Navigation - - E. du Bois.

Descriptive Meteorology - W. L. Moore, LL.D., Sc.D.

Deviations of the Compass Captain E. W. Creak, C.B., F.R.S.,

in Iron Ships. R.N.

Elementary Meteorology - R. H. Scott, M.A., F.R.S.
Encyclopaedia Britannica.

Etude sur les Courbes de G. Hilleret.

hauteur.

Ganot's Physics - - E. Atkinson, Ph.D., F.C.S.

A. W. Reinold, M.A., F.R.S.



Ill

Geodesv .... Colonel A. R. Clarke, C.B., F.R.S.,

R.E.
Glossary of Navigation - Chaplain and Naval Instructor

J. B. Harbord, M.A., R.N.
I Ivdrographical Surveying - Rear-Admiral Sir W. J. Wharton,

K.C.B., F.R.S., R.N.
Rear-Admiral Mostyn Field, C.B.,
F.R.S., R.N.
Lehrbuch der Navigation

(Reichs-Marine-Anit. )
Magnetism, General and Humphrey Lloyd, D.D., D.C.L.

Terrestrial.
Mathematical Instruments - J. F. Heather, M.A.

A. T. Walmisley, M.I.C.E.
Maximum and Minimum Staff Captain Charles Brent, R.X.
Altitude and other Pro- Naval Instructor A. F. Walter,
blems. R.N.

Naval Instructor George Williams,
R.N.
Meteorology, Practical and Sir John Moore, M.A., M.D.,

Applied. D.P.H., D.Sc, F.R.C.P.

Modern Navigation - - Chaplain and Naval Instructor

William Hall, B.A., R.N.
Navigation and Compass Commander W. C. P. Muir, U.S.

Deviations. Navy.

Navigation and Nautical Staff Commander W. R. Martin,

Astronomy. R.N.

Navigation and Nautical Chaplain and Naval Instructor

Astronomy. F. C. Stebbing, M.A., R.N.

Papers in the Philosophical Archibald Smith, F.R.S.

Transactions of the Royal Captain F. J. Evans, F.R.S. , R.N.
Society, 1860, 1861.
Popular Lectures and Ad- Sir William Thomson, LL.D.,

dresses. F.R.S., F.R.S.E.

Practical Manual of Tides W. H. Wheeler, M.I.C.E.

and Waves.
Practice of Navigation - Lieutenant Henry Raper,F.R.A.S.,

F.R.G.S., R.N.
Principal Winds and Cur- Captain 11. Jackson, R.N.

rents of the Globe.
Spherical and Practical William Chauvenet.

Astronomy.
Star At l,i- - - - H. A. Proctor.

Tides and Kindred Pheno Sir G. H. Darwin, K.C.B., F.R.S.

mena.
Watch Make] Handbook - P. .J. Britten.
Weather - - Hon. Ralph Aben-nmiby.

Wrinkles in Practical Navi- Captain S. T. S. Lecky, F R.A.S..

gation. F.R.G.S., R.N.R.

And numerous Government publications.



IV



CONTENTS.



PART I.— NAVIGATION AND NAUTICAL
ASTRONOMY.



CHAPTER I.

Positions on the earth's surface.

Article page

1. Figure of the earth - - - 1

2. Angular latitude and longitude 1

3. Circle of curvature of a meridian - - - - 2

4. The nautical mile - - - 2

5. Length of a nautical mile - - - - - 3

6. The geographical mile - - - - 3

7. Length of the geographical mile - - - - 3

8. Linear latitude and longitude - - - 3

9. The knot - - - - 4

10. The earth approximately a sphere - - - - 5

11. Difference of latitude and difference of longitude - - 5



CHAPTER II.
Direction on the earth's surface.

12. True bearing - - - - 6

13. The magnetic compass - - - - - 6

14. Magnetic variation - - - 7

15. Deviation of the compass - - - - , - 8

16. Methods of applying deviation and variation - - 9

17. The gyro-compass - - - - - - 10



CHAPTER III.
The course and distance by the Mercator's chart.

18. The rhumb Line. Course and distance - - - 11

19. Relation between the arc of a parallel of latitude and the

corresponding arc of the equator - - - - 12

20. The Mercator's chart - - - - - 12

21. Construction of a Mercator's chart - - - - 15

22. Plotting positions on a Mercator's chart - - - 16

23. To find the compass course from one position to another - 17

24. To find the distance from one position to another - - 19

25. To allow for a current when finding the course - - 19



CHAPTER IV.

The covrse and distance by calculation.

Article page

26. Fundamental formulae for the rhumb line - - - 21

27. Formula for the depart ure - - - - 22

28. Formulae for course and distance - - - -2

29. Approximate formula for the departure - - - 23

30. Approximate method of finding the course and distance by

the traverse table - - - - - - 24



CHAPTER V.

The great circle track.



31. The gnomonic chart - - - - - 27

32. Special cases of the gnomonic chart - - - - 30

33. Construction of a gnomonic chart - - - - 30

34. To draw the great circle track on the Mercator's chart - 33

35. Great circle track by calculation - - - - 36

36. Great circle track by Towson's tables - - - 37

37. The composite track - - - - - - 39



CHAPTER VI.

The dead reckoning and estimated positions.

38. The dead reckoning position - - - - 41

39. The estimated position - - - - - 41

40. Working the reckoning by chart - - - - 42

41. Working the reckoning by calculation - - - 43

42. Current by difference between dead reckoning and observed

positions - - - - - - - 46

43. Keeping the reckoning in a tideway - - - 46

44. Track of a ship while turning - - - - 46

45. Keeping the reckoning during manoeuvres - - - 49

46. Examples of keeping the reckoning during manoeuvres - 55



CHAPTER VII.
Position line by observation of terrestrial objects.

47. Inn liability of the estimated position. Position line - 59

48. l'< >s i lion line by compass bearing .... 59

49. Position line by horizontal sextant angle - - 61

50. Position line by distance from an object - - - 61

51. 'I • ial rrfracl ion - - - - - 61

52. Abnormal n fraction - - - - - - 62

68. Altitude of a terrestrial objeol .... 62
54. Depression of a terrestrial objeol - - - - 62

5. r ). 'I'll'- i.l. -• i -\ ■•! ■'.- .-'H ami shore horizons - - - <'»-

56. Formula for the dip of the sea horizon - - - 68

57. I »i tana of the sea horizon ■

58. Formula for the dip of tic- shore horizon

69. Distance bj vertical sextant angle - M
i bore Di tanoe Tables - - - -70



VI



CHAPTER VIII.



Position by observation of terrestrial objects.

Article page

61. To fix the position of a ship - - - - 71

62. Position by cross bearings - - - - - 71

63. Position by bearing and horizontal sextant angle - - 72

64. Position by bearing and distance - - - 73

65. Position by horizontal sextant angles - - - 73

66. Running fix - - - 77

67. Use of soundings in obtaining the position - - - 79



CHAPTER IX.



The heavenly bodies and their true places.

68. Necessity for astronomical observations - - 80

69. The stars - - - - - - 80

70. The constellations - - - - - - 80

71. Designation of bright stars - - - - - 80

72. Magnitudes of stars - - - - - - 80

73. The solar system - - - - - - 81

74. The nebular theory - - - - - - 81

75. How to recognise the stars - - - - 82

76. The movement of the earth - - • - - 84

77. The celestial concave. The ecliptic and celestial equator - 84

78. Positions of heavenly bodies - - - - 85

79. Variation in right ascension and declination - - 87



CHAPTER X.



The Greenwich date and correction of right ascension

and declination.

80. The year and the month - - - - - 88

81. Celestial meridians of observer and heavenly body - - 88

82. The day ....... 88

83. The solar day - - - - - - 88

84. The mean solar day and mean solar time - - - 89

85. Change of time for change of longitude - - - 90

86. The Greenwich date - - - - - - 91

87. Correction of right ascension and declination - - 91

(a) The sun.
(6) The moon.

(c) The planets.

(d) The stars.

88. Adjusting ship's clocks for change of longitude - - 93

89. Standard times - - - - - - 94



Vll



CHAPTER XI.

The zenith distance axd azimuth at the estimated

position.

Article page

90. Connection between a position on the earth and a heavenly

body ....... 96

91. The azimuth - - - 96

92. The zenith distance - - - - - 90

93. The astronomical triangle - - - - - 90

94. The hour angle - - - - - - 97

95. The equation of tune - - - - - 97
90. The right ascension of a meridian (or sidereal time) - 98

97. Formula for the hour angle of a heavenly body - 98

98. Correction of the equation of time - - - 99

99. Change in the right ascension of the mean sun - - 100

100. Correction of the right ascension of the mean sun - - 100

101. Calculation of the zenith distance and azimuth at the

estimated position - - - - 101

102 Azimuth tables and azimuth diagram - 103



CHAPTER XII.



The true zenith distance and astronomical
position line.

L03. The true zenith distance - - - - - 104

104. Formula for astronomical refraction - - - 105

105. Semi-diameter ...... 100

106. Parallax - - - - - - - 107

1"7. Augmentation of the moon's semi-diameter - - - 108

108. Examples of the correction of altitudes - - - 109

L09. The geographical position of a heavenly bod y - - 111

1 10. The true bearing of the geographical position - - 112

111. The circle of position - - - - - 113

112. The astronomical position line - - - - 114

113. The most probable position from a single obsers al ion - 110

114. The value of a single position lino .... 117



CHAPTER XIII.

PoernoK by astbonomioax position ua

ii.".. Position from two or more ob ions - - - 119

llo. Examples of finding posrl ion by plotting and by calculation I 19
Example (1). Position from simultaneous observations bj

plotting (hi on chart, (6) on squared paper - - 120

ExampU (2). Po itiOD from simultaneous olisi-rv ations

bj calculation - - - 123

Example (3). Position from uoo Lve ob ervations (a)

by calculation, (6) bj plotting on the chart - - 125

117. Error in a po ition due to error in the obsen ed altitudes - 127



Vlll



CHAPTER XIII.— continued.

Article page

118. Error in a position due to uncertainty of the error of the

deck watch - - - - - - 129

119. Error in a position due to error in the observed altitudes

and to uncertainty of the error of the deck watch - 131

120. Error in a position due to error hi the reckoning between

the observations - - - - - -131

121. Error in a position due to error in the reckoning between

the observations, and to the error in the observed altitudes 133

122. Error in a position due to error in the reckoning between

the observations, to error in the observed altitudes, and to

uncertainty of the error of the deck watch - - 133

123. Particular case of very large altitudes - - - 133

124. Position by astronomical and terrestrial position lines - 135



CHAPTER XIV



Other methods of determining an astronomical
position line.

125. Meridian passages of heavenly bodies - - - 138

(a) The sun - - - - - - 138

(b) The stars - - - - - - 138

(c) The moon - - - - - - 141

(d) The planets - - - - - - 141

126. Position line by meridian altitude - 142

127. Maximum and minimum altitudes - - - - 146

128. Position line by ex -meridian altitude - - - 146

129. Position line by altitude of Polaris - 150

130. Position line by " Longitude by chronometer " method - 152

131. Longitude by equal altitudes - - - - 154

132. Notes on observations for determining position lines - 160



CHAPTER XV.

Rising and setting of heavenly bodies,
twilight, &c.

133. Hour angles of heavenly bodies when on the rational horizon 163

134. S.M.T. of visible sun -rise and visible sun -set - - 164

135. Twilight - - - - - - - 166

136. S.M.T. of visible moon-rise and visible moon -set - - 168

137. Identification of stars - - - - - 169

138. Torrid, Frigid, and Temperate zones - - - 170



IX

CHAPTER XVI.

The error and rate of the chronometer.

Article page

139. Meaning of the terms error, rate, and accumulated rate - 173

140. System of daily comparisons - - - - 173

141. How to take time accurately with a deck watch - - 174

142. Error of the chronometer by time signal - - 175

143. The mean comparison - - - - - 175

144. Error of the clironometer by astronomical observation - 176

145. The artificial horizon - - - - - 177
14G. Observations in the artificial horizon - - - 178

147. Error of the chronometer by absolute altitudes - - 180

148. Errors involved in absolute altitudes - - 184

149. Error of the chronometer by equal altitudes - 185

150. Formula for the equation of equal altitudes - - 186

151. Errors involved in equal altitudes - - - - 187

152. Example of error of chronometer by equal altitudes - 187

153. Summary of necessary comparisons - - - - 191

154. Notes on observations for error of chronometer - - 191

155. The rate of the chronometer - - - - 194



PART II.— PILOTAGE.






CHAPTER XVII.
The Admiralty chart and artificial aids to navigation.

156. Coasts - - - - - - - 196

157. Dangers • - - - - - 198

158. Depth of water - - - - - 199

1 59. Quality of the bottom - - - - - 199

160. Tides and tidal streams. Currents - 200

161. General abbreviations ..... 201

162. System of buoyage in tlio Uuitiil Kingdom- - - 202

163. System of lighting - - - - -205
164 Fog signals - - - - - - - 208

165. Reliability of f..- -i-nuls ..... 208

166. Submarine bell - - - - - 209

167. Printing <>f the chart - ... 210
ins. Chart correction - - - - - - I'll

169. Reliability of eh . . . - -211

170. Sailing Direction ...... 218



X

CHAPTER XVIII.

The track of the ship and the avoidance of danger in

pilotage waters.

Article page

171. The track - - - - - - - 214

172. Leading marks ...... 215

173. Lines of bearing - - - 216

174. Turning on to a predetermined line - - - - 216

175. Clearing marks - - - 219

176. Clearing bearings - - - 221

177. The vertical danger angle - - - - - 221

178. The horizontal danger angle - - - - - 221

179. Avoidance of danger in thick weather - - - 222

180. Preparing the chart - - - 222

181. Selection of a position in which to anchor - - - 224

182. To anchor a ship in a selected position - - - 224

183. To moor a ship in a selected position - - - 226

184. Example of the preparation of a chart with a view to

anchoring - - - - 228

185. Conning the ship - - - - - - 230



PART III.— THE ATMOSPHERE AND OCEAN.



CHAPTER XIX.

The weather.



186. The atmosphere - - - 232

187. The pressure of the atmosphere - - - - 232

188. Cause and direction of wind - - - 233

189. Permanent winds, Trades and Westerlies - - - 235

190. Periodic winds. Monsoons - - - 236

191. Land and sea breezes - 236

192. Diurnal variation of the barometer ... - 237

193. Local winds - - - - 237

194. Causes of clouds, rain, &c. - - - - , - 238

195. Causes of fog - - - - - - 238

196. Atmospheric electricity - - - - - 239



CHAPTER XX.

Forecasting the weather.

197. The synoptic system of weather analysis - - - 241

198. The seven fundamental forms of isobars - - 242

199. The cyclone - - - - - - - 242

200. The secondary cyclone - - - 243

201. The anti-cyclone - - - - - - 244

202. The wedge - - - - - - - 245

203. Straight isobars - - - - - - 245

204. The V depression - - - - - - 245

205. The col - - - - - - 246

206. Revolving storms - - - 247

207. The indications of the approach of a revolving storm - 249

208. Rules for determining the path of, and avoiding a revolving

storm - - - - 250

209. Weather in the British Islands and North Sea - - 251

210. Storm signals - - - - - - 252

211. Forecasting by a solitary observer - - - - 253



XI



Article
212.
213.
214.
215.
216.
217.
218.
219.
220.
221.



CHAPTER XXI.
Ocean currents, waves. &c.

Currents ......

Atlantic Ocean stream currents

Pacific Ocean stream currents

Indian Ocean stream currem -

Ocean waves .....

To find the dimensions and period of a wave

The specific gravity and colour of sea water

Change of draught on passing from sea to river water

Temperature of the sea

Ice - - - - -



TAGE

256
266

257
258
259
259
260
261
261
261



222
223
224
225
226
227
228
229
230



CHAPTER XXII.

Theoretical tides.

The tide generating forces

The horizontal tide generating force

The lunar and anti-lunar tides

The effect of the earth's rotation

The effect of declination

The effect of parallax

The solar and anti-solar tides

The composition of the lunar and solar tides

Priming and lagging of the tide



264
266
267
268
269
269
270
270
27 1









231.

232.
233.
234.
236.
236.
237.

238.
239.

240.
241.
242.
243.

244.
246.
246.
2 J 7.
248.
249.
260.
28 1 .



CHAPTER XXIIL

Observed tides and use of ttdts tables.

Tidal streams.

Disagreement between theory and observation

Rise and range of a tide .....

The primary and derived tide waves

The age of the tide ......

The amount of the priming and lagging

The iiitun establishment of a port ....

'I 'o find the time of high water on any day from the mean
tblishment ......

'I'll- \ -uIlmi- establishment of a port-, or the 1 1 .U.K. and C. -
T<> I iiK I the time of hiidi water on any da\ from the ELW.F,
and C. - - - -

of finding the time of high water
I Kurnal inequality ......

Tide prediction. Standard porta ....

To find the height o! the tide at any time, \,-.
Examples of finding the height of the tide at any time

iparison between the t Idea at i wo places. Tidal constant

■ I of meteorological condit i<
The cause of t idal b1 reams
Tii la] bream in a channel
'l err of turning of tii Levi I reams
The I., i . of tidal breams
The tidal streams round the British Island



273
273
276
276
276
270

277
27S

27S
280
280
281
281
2s 2
286
287
288
288
289
289
290



Xll

PART IV.— NAVIGATIONAL INSTRUMENTS.



CHAPTER XXIV.

The magnetic compass.

The magnetism of the earth and ship.

Article page

252. Magnetism - - - - - - - 291

253. The effect of a magnet on an isolated pole - - - 293

254. The molecular theory of magnetism .... 295

255. Magnetic induction - - - 295

256. Artificial magnets - - - 296

257. Effects of temperature on magnets - 298

258. Terrestrial magnetism ..... 298

259. Changes in the variation ..... 299

260. Obtaining the variation by observation on shore - - 299

261. To find the true bearing of an object by observation - 300

262. Example of finding variation on shore - - - 301

263. Local attraction - -... 304

264. The compass - - - - 304

265. To compare the earth's horizontal force at two places - 305

266. The permanent magnetism of a ship - - - 305

267. The induced magnetism of a ship - 306

268. The horizontal forces at the compass when the ship heels - 311

269. The sub-permanent magnetism of a ship - - - 312



CHAPTER XXV.

The magnetic compass — (continued).

The analysis and correction op the deviation.

270. The deviation of the compass - 314

271. The principle of compass correction - - - - 316

272. The exact expression for the deviation of the compass - 316

273. The meaning of A - - - - - 317

274. The approximate expression for the deviation - - 318

275. The component parts of the deviation - - - 318

276. Relations between the exact and approximate coefficients - 319

277. To find the approximate coefficients from observation - 320

278. To find the exact coefficients - 321

279. The correction of coefficient B' 322

280. The correction of coefficient C" - - - 324

281. The correction of coefficient D' - - - 324

282. The correction of coefficient E' 326

283. The correction of the total quadrantal deviation - - 326

284. The induction in the soft iron correctors due to the compass

needles - - - - 329

285. The coefficient A' - 330

286. To obtain X by observation - - - 330

287. The effect of spheres on X and the formula for X 2 - - 331

288. The effect of sub -permanent magnetism - - - 332

289. The effect of lightning - - - - - 333

290. The expression for the deviation when the ship heels - 333

291. The meaning of n - - - - - 335

292. The correction of the heeling coefficient J - - * - 335

293. The heeling error instrument .... 335

294. The correction of heeling error in harbour - - - 337

295. The correction of heeling error at sea - - - 338

296. The change of the heeling error due to change of magnetic

latitude ... - - - - • 338



Xlll

CHAPTER XXVI.

The magnetic compass — (continued).
The description and practical correction of the compass.

Article page

297. The bowl of the Chetwynd compass - - - 340

298. To remove a bubble from the com.pi - - - 341

299. The binnacle - - - - - - 34 1

300. The Thomson compase - - - 343

301. The azimuth mirror - - - 344

302. How to take bearing - - - 344

303. The bearing plate or Pelorus - 346
::<»4. The compass m a conning to \\vr - - - 347
305. Precautions to be observed with regard to electrical instru-
ments, &c. - - - 347

6. To obtain the deviation by observation - - - 351

307. To find the true bearing of an object by the Mercator's chart - 353

308. The adjustment of compasses - 354

309. To obtain the deviation of and to adjust a between-deck

compass - - - - 355

"10. Swinging ship for deviation - 356

311. Necessity for frequent observations for deviation - - 358

312. The criteria of a good deviation table - - - 358

313. Obtaining the variation by observation at sea 359



CHAPTER XXVIT.
The gyro-compass.



:"'. 14. Gyrostats and gyroscopes - - - 360
315. The effect of a couple on a gyrostat - - - -.360



Online LibraryGreat Britain. AdmiraltyManual of navigation, 1914 → online text (page 1 of 46)