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ABL-10

Piloting and Navigation. ABL-10. Instructor: George Crowl. Requirements (1). a. Describe the deck log kept aboard your ship's principal craft. Keep a complete deck log for three cruises. b. Lay a course of at least three legs and execute it using dead reckoning.

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ABL-10

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  1. Piloting and Navigation ABL-10 Instructor: George Crowl

  2. Requirements (1) a. Describe the deck log kept aboard your ship's principal craft. Keep a complete deck log for three cruises. b. Lay a course of at least three legs and execute it using dead reckoning. c. Demonstrate your ability to fix your position by the following methods: taking bearings from two known objects, running fix, and estimated position.

  3. Requirements (2) d. Establish distance from a known object by “double the angle on the bow” and explain how to set a danger angle. e. Discuss how GPS (Global Positioning System) operates and the purpose of waypoints. While underway, demonstrate your ability to use a GPS while using three different waypoints. f. Discuss the method of establishing a radar fix.

  4. Deck Logs a. Describe the deck log kept aboard your ship's principal craft. Keep a complete deck log for three cruises.

  5. 10a. Deck Log

  6. Execute Course Using DR b. Lay a course of at least three legs and execute it using dead reckoning.

  7. 10b. Execute Course Using DR Plot three legs, totaling about an hour's cruise. Start and end at identifiable points. Use a motor-driven boat. Sailboats under sail make this much harder. A closed course, such as 120°M, 360°M, 240°M is convenient. Pay attention to speed and heading. Determine your error at the end.

  8. Fixing Methods c. Demonstrate your ability to fix your position by the following methods: taking bearings from two known objects, running fix, and estimated position.

  9. 10c(1). Two-Bearing Fix Take bearings using a hand-bearing compass.

  10. Plan a Fix DR ahead to a good time and place for a fix. Select someplace with good bearing cuts (90° is ideal, should not be less than 30°). Select identifiable landmarks (towers, points of land, hill tops, etc.) Orient yourself so you have the right points.

  11. Execute the Fix Two bearings within a minute Write the time and bearings down! Convert to true OR use parallel rules with compass circle Plot lines Crossing point is fix

  12. 2-LOP Fix (Line of Position) Take two bearings Plot mag bearings backwards OR Apply variation backwards and plot true bearing backwards EXERCISE – What do we plot? SSPR p. 27

  13. 3-Bearing Fix Take 3 mag bearings w/handheld compass Convert to true using deck log Plot RECIPROCAL from the actual point Triangle is your position

  14. 10c(2). Running Fix Often used to establish distance from an object or a shore. May take a long time. Take a bearing. Take a second bearing. Advance the 1st bearing to the 2nd bearing. GSxT

  15. Running Fix Take an initial bearing and time, hold course and speed. Plot initial bearing. Move it along course for amount of time run. Plot second bearing. Wherethey cross is fix.

  16. 10c(3). Estimated Position Normal DR position to start Add various vectors Current (set / drift) Heading / speed error Single line of position (LOP)

  17. Set and Drift Set = direction Inbound or outbound tidal flow Ocean current movement Drift = speed Set – SE, drift 3 K Set ENE, drift 5 K

  18. Estimated Position (EP) DR + Set (135°) and Drift (5K) 1445 080° @ 10K 135° @ 5K 1345 Track over ground 100° @ 13K 1445 EP

  19. Special Techniques d. Establish distance from a known object by “double the angle on the bow” and explain how to set a danger angle.

  20. 10d(1). Double the Angle on the Bow Pick any angle, 15°- 45°. Take first bearing, time. Double it. Take time of 2nd bearing. Figure distance traveled from GS. 2nd bearing angle & time is fix. Distance is distance traveled from 1st to 2nd bearing. (Isosceles triangle) GSxT

  21. Double the Angle Take an angle off the bow (22.5°, 30°, 45°), start a time, hold your course and speed. When you DOUBLE it, stop your time. Calculate distance run. That is the distance to theobject, and the angle fromyour heading.

  22. 10d(2). Danger Bearing Determine the area to avoid. Plot a line (bearing) that keeps you clear. If you need to stay on the LEFT of the line, keep your bearing Not Less Than (NLT) the bearing. If you need to stay on the RIGHT of the line, keep your bearing Not More Than (NMT). NLT 252M

  23. Set a Danger Angle Determine how close you can go to the danger Read the angle, then set the “danger bearing” Steer between or beyond the bearing SSPR p. 23

  24. Global Positioning System e. Discuss how GPS (Global Positioning System) operates and the purpose of waypoints. While underway, demonstrate your ability to use a GPS while using three different waypoints.

  25. 10e. Global Positioning System (GPS) Satellites circle the earth at 55° angle to the equator. Everything is precisely timed to provide location Lock on four satellites provides 3-D fix. Movement over time gives track and groundspeed.

  26. Global Positioning System (GPS) Normal GPS operation measures time delays SSPR p. 30

  27. Waypoints Waypoints – places you are going along the way! Marker 2 to Redfish to HSC 69 … Coordinates, elevation, description (from list?) GPS provides steering and calculates time to arrival at your current speed 069 HSC 69 002 Mkr 2 018 Redfish

  28. Exercise! Handout Compass GPS Packet (GPS, Quick Start, Instructions) We do ded reckoning on land, with a compass and timing our walks

  29. Radar Use and Fixing f. Discuss the method of establishing a radar fix.

  30. 10f. Radar Fixing FIRST – the primary purpose of sea-borne radar is collision avoidance! If a bright spot is getting closer to you and not changing bearing, take avoiding action!

  31. Radar Bearings

  32. Range and Bearing Range and bearing 005°T/2.5NM point of land Dashed lines

  33. Multiple Ranges Ranges on nearby land shapes Plot using drawing compass arcs

  34. Questions?

  35. Bonus Information The information below is not required for advancement, but is useful for practical point-to-point navigation.

  36. Practical Sea Scout Navigation Memorize mental speed calculations 4 K, 15 min = 1 NM 5 K, 12 min = 1 NM 6 K, 10 min = 1 NM 30 min = 1/2 your speed 20 min = 1/3 your speed 15 min = 1/4 your speed 12 min = 1/5 your speed 10 min = 1/6 your speed 6 min = 1/10 your speed

  37. Normal Navigation Monitor average heading and speed Calculate ETA to turning point Plan fix about 15-20 minutes short of TP Plot DR for that time for orientation Take fix, plot fix and time

  38. DR Ahead Measure distance, calculate speed Extend track line from departure through fix, add 1/10 your speed (speed 4.5K, extend line 0.45NM). This is your DR for 6 minutes later.

  39. Alter Heading Measure course to destination, calculate compass heading, tell bosun / skipper to turn at DR time. Measure distance, apply speed, calculate ETA, announce it.

  40. Remember “The perfect is the enemy of the good.” A timely approximate solution is better than a late perfect solution. You can continue to modify a timely approximation.

  41. Questions?

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