Lectures in Navigation Part 23

_At Noon._ L.A.T. 00h 00m 00s (_) 37 59' S + W. Lo. 4 41 58 ----------- IE + 10 G.A.T. 4h 41m 58s ------------ E.T. (sign reversed) + 12 34 37 59' 10" ----------- HE 8 55 G.M.T. 4h 54m 32s 17 ---------- -(-)- 38 08' 22" S 51 51' 38" N (ZD) 18 51 12 S (Dec.) ---------- 33 00' 26" N. Lat. in at Noon.

Lo. Factor = .93 Lat. by Obs. 33 00' 26" N Lat. Diff. 9.5 Lat. by D.R. 32 50' 54" N ------ ------------ Diff. Lo. 8.83 Lat. Diff. 9' 32"

Since Obs. Lat. is East of D.R. Lat. on Line of Pos.

Lo. Diff. is applied East.

/ Lo. by D.R. 70 29' 26" W / Lo. Diff. 8 50 E Obs. Lat. * ------------ / Lo. in at Noon 70 20' 36" W D.R. Lat. *

_By Dead Reckoning from Noon to Noon_

=========================================================== Course | Dist. | D. Lat. | Dep. | D. Lo.

----------+---------+-----------+--------+----------------- N 35 E | 78 | 63.9 | 44.7 | 176' or 2 56'

N 40 E | 138.5 | 106.1 | 89. | N 39 E | 24.5 | 19. | 15.4 | | | ----- | ---- | | | 189. | 149.1 | ===========================================================

Lat. left. 30 01' N Lo. left 73 47' 20" W 3 09 N 2 56 E --------- ------------- Lat. in 33 10' N Lo. in 70 51' 20" W

Min. Lat. 31 35'

The Watch Time of Local Apparent Noon

Date--Jan. 26, 1919

G.A.T. of A.M. Sight 1h 16m 04s Lo. in T. of A.M. sight 4 43 12 ----------- L.A.T. 20h 32m 52s Total Time to Noon 3h 27m 08s

Course to Noon -- 39 Change in Lo. per hr. -- 5.2', 21s

3600s + 21s = 3621s

3 X 60 = 180 27 ----- 207 60 ------ 12,420 08 -------- 3621 ) 12,428 (3.43 hrs 10,863 ------ 15,650 14,484 ------ 11,660 10,863 ------

3.43 hrs = 3h 25m 48s W.T. of A.M. sight 8 31 16 A.M.

---------- W.T. of L.A.N. 11h 57m 04s A.M.

ANSWER.

_By D.R._ Lat. 33 10' N Lo. 70 51' 20" W

_By Observation_ Lat. 33 00' 26" N Lo. 70 20' 36" W

_Dev. at 8:30 A.M._ 1 E

_W.T. of L.A.N._ 11h 57m 04s A.M.

FRIDAY LECTURE

DAY'S WORK

At sea, November 28th, 1918. Departure taken at noon in Lat.i.tude 20 50'

N, Longitude 73 15' 20" W. Log at noon registered 34. Sailed on course p.s.c. 73, Deviation 3 E, Variation 1 W until twilight when log registered 152.

Changed course to E 3/4 N p.s.c. and observed alt.i.tude of Star Aldebaran, East of meridian 37 10' 10" and bearing by compa.s.s N 89 E, Variation 2 W. WT 8h 10m 16s. C-W 4h. 51m 30s. CC 4m 08s slow. IE 1'

10" off the arc. HE 38 ft.

s.h.i.+p steamed on this course, in heavy fog and rain, until 2:30 A.M. when log registered 200. s.h.i.+p changed course to E 1/2 N (true) and steamed at 8 knots per hour until 6:30 A.M. when weather cleared and observed alt.i.tude Star Polaris 21 04' 20" N. WT 6h 35m 47s A.M. C-W 4h 51m 30s.

Same IE, HE and CC.

s.h.i.+p continued on same course and speed until about 9:30 A.M. when observed alt.i.tude of (_) 38 45' 20". WT 9h 39m 10s A.M. C-W 4h 51m 30s.

Same IE, HE and CC.

s.h.i.+p then steamed a true course of 93 at a rate of 10 knots per hour until noon when log registered 294 and observed meridian alt.i.tude (_) 46 49' 30". Same IE, HE and CC.

Required 1. D. R. position at noon.

2. Position by observation at noon (corrected for Longitude by a factor).

3. Deviation at 8:10 P.M.

4. Watch Time of Local Apparent Noon.

SAt.u.r.dAY LECTURE

DAY'S WORK

At sea, April 21st, 1918. Departure taken from noon position in Lat.i.tude 31 50' N, Longitude 76 30' 31" W. Log registered 128 at noon.

Course p.s.c. until about 4:30 P.M. was N 10 E. Deviation 1 W.

Variation 3 W. At about 4:30 P.M. observed alt.i.tude of sun's lower limb 25 13' 10" and bearing by compa.s.s N 87 W. WT 4h 26m 46s. C-W 5h 04m 52s. CC 1m 03s slow. IE 0' 10" off arc. HE 29 ft. Log registered at this time 188.

Course was then changed to NE x N (true). Weather cloudy. At about twilight clouds broke away and observed alt.i.tude of Star Procyon West of meridian 40 01' 00". CT 1h 37m 28s A.M. CC 1m 03s slow. IE 0' 10" off arc. HE 29 ft. Log registered 236. Continued on same course until midnight, at which time log registered 290. At midnight s.h.i.+p ran into dense fog and slowed down to 8 knots until about 6:30 A.M., when fog blew away and observed alt.i.tude of Star Polaris 35 29' 10" N. WT 6h 32m 14s A.M. C-W 4h 59m 02s. IE 0' 10" off arc. CC 1m 03s slow. HE 29 ft.

From 6:30 A.M. s.h.i.+p steamed a true course of N 32 E until noon at a rate of 15 knots per hour, at which time a meridian alt.i.tude of the (_) was observed 65 37' 10" S. Log registered 424. HE 29 ft. IE 0' 10" off arc. CC 1m 03s slow.

Required 1. D. R. position at noon.

2. Position by observation at noon (corrected for Longitude by a factor).

3. Deviation of Compa.s.s at 4:30 P. M. sight.

4. Watch Time of Local Apparent Noon.