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Maneuvering Boards Review

Maneuvering Boards Review. Maneuvering Boards Review. AGENDA: Definition of Relative Motion True Bearings vs. Relative Bearings The Maneuvering Board The Relative Plot Application: Example of Collision Avoidance (CPA). True vs. Relative Motion.

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Maneuvering Boards Review

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  1. Maneuvering Boards Review

  2. Maneuvering Boards Review • AGENDA: • Definition of Relative Motion • True Bearings vs. Relative Bearings • The Maneuvering Board • The Relative Plot • Application: Example of Collision Avoidance (CPA)

  3. True vs. Relative Motion True vs Relative Motion: Understanding the difference between true and relative motion is essential in excelling in moboards. • True Motion: the movement of an object with respect to the surface of the earth. • Relative Motion: the apparent movement of an object with respect to another moving object.

  4. Relative Movement • Represented on maneuvering board • Consider yourself onboard ship monitoring actions of other ships • Find actual course and speed required to bring about desired change in relative position in maneuvering a ship at sea

  5. True vs. Relative Bearings • Line of Sight (LOS) = straight line between an observer and an object. • True Bearings (T) = direction measured with respect to true of geographic north. • Ship’s heading (°T) • Relative Bearings (R) = direction measured with reference to the ship’s longitudinal axis.

  6. Line of Sight • Each line of sight has two directions which differ by 180 degrees • Heading of either ship does not affect the LOS

  7. True Bearings • True Bearing - bearing measured clockwise from true north in degrees to line of sight • heading of ship does not affect bearing • reference line true north remains same regardless of movement

  8. N TRUE BEARINGS 000T Ship’s course = 045T ? W E 090T 135T S

  9. Relative Bearings • Relative Bearing - measured in degrees from ships heading (course) clockwise to the observed object • Remember - course of reference ship will always affect relative bearing because it is reference line for relative bearing

  10. Remember… • Never plot relative bearings on a maneuvering board • Must convert relative bearings to true bearings before plotting

  11. RELATIVE BEARING N 270R E W 090T 180R 000R 090R 180 T S

  12. RELATIVE BEARINGS N Ship’s course = 045T ? W E ? ? 135T S

  13. RELATIVE BEARINGS N Ship’s course = 045T 000R W E 090R 180R 135T S

  14. Converting True and Relative Bearings • Converting relative bearing to true is accomplished by using the following formula: TB = SH + RB • Example: Contact bears 270°R, ship is on course 330°T. What is the true bearing to the contact? TB = SH + RB TB = 330° + 270° TB = 600°  240°T

  15. The Maneuvering Board • Purpose: a tool to plot the position of a ship relative to the position of another ship. • Applications: • Collision Avoidance … CPA’s • Formation Steaming … Station Keeping • RDVU/Intercept … UNREP’s • Wind Problems … Desired wind

  16. The Maneuvering Board • Description: • Ten concentric circles • Bearing lines radiating from the center. • Five scales provided. • Nomogram provided.

  17. The Relative Plot • Relative Plot: Defined as a polar representation of the successive positions of one or more moving objects with respect to a reference position. This reference position will normally be your own vessel; the bearings and ranges are taken from your radar.

  18. The Relative Plot • The maneuvering board (relative plot). • E - reference ship (placed in the center) • M1, M2 - any maneuvering ship • DRM - Direction of Relative Motion • MRM - Measure of Relative Motion • SRM - Speed of Relative Motion • CPA - Closest Point of Approach

  19. Closest Point of Approach (CPA) • Made up of three parts • Range/Distance • Bearing • Time

  20. Setting up a MoBoard • First Determine Scale • Speed • Distance

  21. D S

  22. Setting up a MoBoard • Second plot yourself in the center of the MoBoard • Then plot your ship’s • Speed • Distance • For Example you are on a course of 050T at a speed of 15 kts.

  23. D S r e

  24. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. 1. Plot M1(points on the moboard the correspond to the bearings and ranges of the contact)- note, use a 2:1 scale.

  25. D S r M1 e

  26. Example: CPA Determining CPA: At 0815 the same contact bears 300ºT, at 10,000 yards. Find the CPA (bearing, range, and time): 1. Plot M1 and M2 (points on the moboard the correspond to the bearings and ranges of the contact)- note, use a 2:1 scale.

  27. D S M2 r M1 e

  28. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 1. Plot M1 and M2 (points on the moboard the correspond to the bearings and ranges of the contact)- note, use a 2:1 scale. 2. Find DRM - 073ºT

  29. D S M2 r M1 e

  30. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 1. Plot M1 and M2 (points on the moboard the correspond to the bearings and ranges of the contact)- note, use a 2:1 scale. 2. Find DRM - 073ºT 3. Find MRM - 7,500 yards

  31. D S MRM M2 r M1 e

  32. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 4. Enter nomogram with 7,500 yards and 15 minutes (elapsed time between interval - 0800 to 0815) to find SRM - 15 knots

  33. D S MRM M2 r M1 e

  34. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 4. Enter nomogram with 7,500 yards and 15 minutes (elapsed time between interval - 0800 to 0815) to find SRM - 15 knots 5. CPA bearing (Add or subtract 90 to/from DRM to determine CPA Bearing) - in this case subtract 90: 073ºT - 090ºT = 343ºT

  35. D S 343T MRM 90 M2 r M1 e

  36. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 6. CPA Range - measure from the center of the maneuvering board to CPA point to determine CPA range - 7,500 yards

  37. D S MRM CPA Range M2 r M1 e

  38. Example: CPA Determining CPA: At 0800 a contact bears 280ºT, at a range of 16,000 yards. At 0815 the same contact bears 300ºT, at 10,000 yards. Find CPA bearing, range, and time: 7. CPA Time -measure the distance between M2 & CPA point. This distance is 6,900 yards. Enter the nomogram with 6,900 yards and an SRM of 15 knots - 14 minutes (add this to time of M2 to find CPA time)

  39. D S MRM CPA Range M2 r M1 e

  40. Questions?

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