Emergency Navigation

1. Emergency Navigation Navigation Chapter 7 1

2. Emergency Reference Material • “Bowditch”, Chapter 26 • Complete online version at http://www.nga.mil/portal/site/maritime/

3. Learning Objectives • Provision an emergency navigation kit. • Construct emergency plotting charts. • Determine destination coordinates mathematically from course & distance traveled.

4. Emergency Planning • Emergency Navigation - dramatically changed. • IMPORTANT: Remain near scene of emergency. • Notify authorities – worldwide comm. & maritime safety systems • EPIRBs, PLBs, SART, & satellite phones.

5. Emergency Planning If electronics fail & vessel not in danger: Stay on board Use DR & Celestial navigation. Be Prepared – backup charts & tools. Never be completely dependent on electronic methods. Maintain regular practice in celestial & DR techniques. 5

6. Emergency Navigation Kit • Pre-stocked, waterproof kit of navigation supplies & equipment: • Hand-held GPS, with waypoints & batteries • EPIRB & SART • Hand bearing compass • Paper charts & notebook for Log, calculations • Paper, pencils, plotting tools, spare batteries • Plastic Sextant & reliable waterproof timepiece • Scientific Calculator & Nautical Almanac • Marine & AM-FM radios

7. Most Probable Position (MPP) • Accurate position info – always important, especially during approach to landfall. • MPP - represents best position estimate. • DR - augmented with leeway, set/drift, LOPs/bearings, sounding, weather, etc. • Requires experience & judgment • Always practice good navigation procedures.

8. Plotting Sheets • Constant Latitude Scale Small Area Plotting Sheet (CLS-SAPS) • Create your own plotting sheets: • Method I • Method II

9. Method 1

10. Method II

11. Dead Reckoning • Dead Reckoning - always available in some form. • In an emergency with electronic systems unavailable – DR techniques become extremely important. • Don’t underestimate its life saving potential!

12. Simplified Traverse Table • Can be used to determine arrival point without plotting. • Requirements: • Starting position • Course - to determine Course Angle • Distance traveled

13. Course Angle Angle between course line & adjacent meridian. Reckoned from N or S, toward E or W. Examples: 075°T => N75°E 155°T: 180° - 155° = 25° => S25°E 236°T: 236° - 180° = 56° => S56°W 300°T: 360° - 300° = 60° => N60°W 13

14. Using Traverse Table To find Difference of Latitude: • Enter table with course angle. • Multiply distance run by factor from table.

15. Using Traverse Table - cont To find DLo: • Enter table with course angle complement (90° - course angle) • Multiply distance run by factor from table • Result: called departure - nautical miles • Calculate mid-Lat • Re-enter table with mid-Lat value • Divide departure value by factor • Result: Difference of Longitude, DLo

16. Example 1:Using Traverse Table • A vessel travels 26 nm on course 205°T • from L 41°44´N, Lo 56°21´W. • Find the coordinates of the point of arrival. • Solution: • Course angle: 205° – 180° = S 25° W • Complement: 90° – 25° = 65° • Their factors are 0.9 and 0.4, respectively.

17. Example 1:Using Traverse Table • Difference of Lat: 26 nm x 0.9 = 23.4’, rounded to 23’ • Course is SW: subtract Difference of Lat from Lat of starting point. • Lat, point of arrival: • 41°44´ N • – 23´ • 41° 21´ N

18. Example 1:Using Traverse Table • Departure: 26 nm x 0.4 = 10.4 nm • Find mid-Lat: departure & arrival Lat: • 41°44´ – (23.4´÷ 2) = 41°32.3´ • rounded to 41°32´N • Mid-Lat factor = 0.7 DLo = 10.4 nm ÷ 0.7 = 14.9´ rounded to 15´

19. Example 1:Using Traverse Table • Course is SW: add DLo to Lo of starting point. • Lo, point of arrival: • Lo 56° 21´ W • + 15´ DLo • 56° 36´ W • Answer: L 41°21´N, Lo 56°36´W.

20. Skill 1:Estimate Your Position • A vessel travels 42 nm on course 325°T from L 32°25´N, Lo 165°36´E • Find the coordinates of the point of arrival. • Solution:Course angle = 360°-325° = N 35° W Complement = 90°-35° = 55° • Extract corresponding factors; 0.8 & 0.6, respectively Skip

21. Skill 1:Estimate Your Position • Difference of Lat: • 42 nm x 0.8 = 33.6´, rounded to 34´ • Departure: • 42 nm x 0.6 = 25.2 nm • Course is NW: Add Difference of Lat to Lat of starting point. • Lat, point of arrival: • 32°25´ + 34´ = 32° 59´N

22. Skill 1:Estimate Your Position • Mid-Lat = 32° 25´ + (34´÷ 2) = 32° 42´N • Factor for this value = 0.8 • DLo = 25.2 nm ÷ 0.8 = 31.5´, rounded to 32´ • Course is NW in East Lo: subtract DLo from the departure Lo. • Lo, point of arrival: 165°36´E – 32´ = 165° 04´E • Answer: L 32°59´N, Lo 165°05´E

23. Deck Log • Maintain a Deck Log throughout emergency • Initial log items: • Date, time & position • Pertinent info relating to the emergency, its effect on crew, vessel, equipment • Make frequent instrument readings • Log each changed reading • Vessel heading affects DR position

24. Life Raft Navigation • Initiate EPIRB & SART messages • Begin celestial navigation if possible. • Star Overhead to determine position. • Remember: Emergency navigation skills are worthless unless practiced! • “Practice makes perfect”

25. Summary Provision an emergency navigation kit. Construct emergency plotting charts. Determine destination coordinates mathematically from course & distance traveled. 25

26. Emergency Navigation End of Navigation Chapter 7 26