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Question

The statements below show the relationship of Whole Circle Bearing (WCB) with the Quadrantal Bearing (QB) for quadrant designations North-East (N-E), North-West (N-W), South-East (S-E) and South-West (S-W). Which of the following statements is/are correct?

The correct answer is
For the quadrant S-W, QB = WCB -180°

The question asks to identify the correct relationship between Whole Circle Bearing (WCB) and Quadrantal Bearing (QB) for specific quadrants.

Understanding Bearing Systems

Whole Circle Bearing (WCB): Measured clockwise from the North direction, ranging from 0° to 360°.

Quadrantal Bearing (QB): Measured from the North or South meridian towards East or West, always an acute angle (0° to 90°), denoted with quadrant (e.g., N 30° E, S 45° W).

Analyzing Quadrant Relationships

Let's determine the formula for the South-West (S-W) quadrant (WCB between 180° and 270°):

  • In the S-W quadrant, WCB is measured clockwise from North, past East (90°) and South (180°).
  • QB for S-W is measured from the South meridian towards the West.
  • The angle measured from South towards West is the difference between the WCB and the South meridian (180°).
  • Therefore, the value of QB is $WCB - 180°$. The notation is S $(WCB - 180°)$ W.

This matches statement 1: For the quadrant S-W, QB = WCB -180°.

Evaluating Other Options

  • Option 2 (S-W, WCB = 180° – QB): This is incorrect. Rearranging the correct formula (QB = WCB - 180°), we get WCB = QB + 180°.
  • Option 3 (N-W, WCB = 180° - QB): This is incorrect. For the N-W quadrant (WCB 270° to 360°), QB is measured from North towards West. The formula is QB = 360° - WCB, or WCB = 360° - QB.
  • Option 4 (N-W, QB = WCB 360°): The notation is ambiguous. If it means QB = 360° - WCB, it is correct for the N-W quadrant. However, given the structure and the confirmed correctness of statement 1, and the ambiguity of this option's notation, statement 1 is the most accurate and standard representation.

Based on the standard conversion formulas, statement 1 correctly represents the relationship for the S-W quadrant.

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Important Questions from Compass

  1. The magnetic bearing of a line in the year 1990 was found to be N 40°30′ W and magnetic declination was 3°30′ E. If the present magnetic declination is 2°10′ W, the magnetic bearing now (in reduced bearing system) would be
  2. The bearing of the line AB from North is $143^\circ40\prime$ and angle ABC measured in clockwise direction is $309^\circ30\prime$. The bearing of line BC in Quadrantal Bearing System is ___________
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