84 



UNITED STATES COAST GUARD 



10. GREAT CIRCLE SAILING. 



Enroute from New London, Conn, to 

 Sao Luiz, Brazil a vessel leaves point 

 "A" at Latitude 41°-06' North, Longi- 

 tude 71°-42' West for point "B" at Lati- 

 tude 01 "-17' South, Longitude 44°-55' 

 West. 

 Find: 



Great Circle Distance. 



Great Circle Initial Course. 



Great Circle Final Course. 



Great Circle Latitude of Vertex. 



Great Circle Longitude of Vertex. 



Great Circle Longitude of Equator 

 Crossing. 



Great Circle Course at Equator. 



From Farallon Island L. H., San 

 Francisco, at Latitude 37°— 42' North, 

 Longitude 123°-00' West, to San Ber- 

 nardino Island L. H., in the Phillipine 

 Islands, at Latitude 12 "-45' North, 

 Longitude 124°-17' East. Find: 



Great Circle Distance. 



Great Circle Initial Course. 



Great Circle Final Course. 



Great Circle Latitude of Vertex. 



Great Circle Longitude of Vertex. 



The Latitude of Three Points 

 Whose Longitudes Differ 5°, 10°, and 

 15°, Respectively, from that of the Ver- 

 tex. 



11. PILOTING. 



In piloting a vessel through a curved 

 section of a tidal river, where would you 

 find the deepest water and the most 

 rapid current? 



Name some of the factors you would 

 consider in selecting a good anchorage 

 site. 



Describe a method of finding distance 

 from an isolated object which is within 

 a moderate distance, such as an islet or 

 a vessel, over which the horizon may be 

 seen. 



Heading east on a dark night, you are 

 a mile and a half north of a light which 

 is located on the east end of a reef with 

 no other aids to navigation visible. An 

 outlying shoal lies two and a half miles 

 to the eastward of the light. With no 

 appreciable current and no range-finder 



available, describe how you would round 

 the light, passing between the reef and 

 the outlying shoal and maintaining the 

 same distance off the light, until on a 

 course of southeast for open water. 



How may the sextant be used in 

 order to round a lighthouse in the day- 

 time so as to maintain a constant dis- 

 tance off the lighthouse until on a de- 

 sired change of course? 



When making a landfall, if soundings 

 should fail to agree in a general way 

 with those shown on the chart and a 

 marked departure from the characteris- 

 tic bottom shown on the chart is noted, 

 what should be done? 



Describe the use of depth contours 

 (curves of equal depth) in navigation. 



Note: Problems may be given pertaining to piloting which are under other titles in this book. 



12. AIDS TO NAVIGATION. 



How would you estimate the power 

 of a light whose candlepower is not 

 given? 



How do you obtain information about 

 foreign buoyage? 



Referring to the sketch: 



(a) What type buoy is the orange 

 and white horizontally banded buoy 

 shoAvn, and for what purpose would it 

 be placed? 



(b) How would such a buoy be in- 

 dicated on a chart? 



ORANG£ 



WHITE 



ORANGE 



WHITE 



ORANGE 



