Which of the following statement is CORRECT for whole circle bearing?
It is always measured from north end of the reference.
Understanding Whole Circle Bearing Measurement
Whole Circle Bearing (WCB) is a system used in surveying to specify the direction of a line with respect to the magnetic or true meridian. It is a single angle that uniquely defines the direction of any line.
What is Whole Circle Bearing?
In the Whole Circle Bearing system:
- The bearing is always measured from the North end of the reference meridian (either magnetic or true north).
- The measurement is always taken in a clockwise direction.
- The angle can range from $0^\circ$ to $360^\circ$.
Analyzing the Given Statements
Let's evaluate each statement based on the definition of Whole Circle Bearing:
- Statement 1: "It is always measured in anticlockwise direction."
This is incorrect. Whole Circle Bearing is always measured in the clockwise direction from the North meridian.
- Statement 2: "It is always measured in anticlockwise direction from south end of the reference."
This is incorrect. WCB is measured clockwise from the North end, not anticlockwise from the South end.
- Statement 3: "It is always measured in clockwise direction from south end of the reference."
This is incorrect. While it is measured clockwise, the reference end is always North, not South.
- Statement 4: "It is always measured from north end of the reference."
This is correct. The fundamental principle of Whole Circle Bearing is that the angle is measured from the North end of the meridian.
Comparison with Quadrantal Bearing
It's useful to compare Whole Circle Bearing (WCB) with the Quadrantal Bearing (QB) system to highlight the differences:
| Feature | Whole Circle Bearing (WCB) | Quadrantal Bearing (QB) |
|---|---|---|
| Reference Direction | Always North | North or South (whichever is nearer) |
| Measurement Direction | Always Clockwise | Clockwise or Anticlockwise (whichever is nearer to the line) |
| Angle Range | $0^\circ$ to $360^\circ$ | $0^\circ$ to $90^\circ$ |
| Representation | A single angle (e.g., $120^\circ$, $270^\circ$) | Angle with cardinal directions (e.g., $S\;30^\circ\;E$, $N\;45^\circ\;W$) |
From the analysis, Statement 4 accurately describes a key characteristic of Whole Circle Bearing.
Conclusion on Whole Circle Bearing
The Whole Circle Bearing system simplifies direction measurement by using a single angle measured consistently. This consistent measurement direction (clockwise) and reference point (North) makes it a widely used system in various applications, including land surveying and navigation.
Revision Table: Key WCB Facts
| Characteristic | Description for WCB |
|---|---|
| Starting Point | North direction |
| Direction of Measurement | Clockwise |
| Range of Angle | $0^\circ$ to $360^\circ$ |
Additional Information on Bearings in Surveying
Bearings and angles are fundamental concepts in surveying used to define the direction of lines. Understanding the different systems like Whole Circle Bearing and Quadrantal Bearing is crucial for accurate mapping and layout work. The reference meridian can be true north (geographic north) or magnetic north (indicated by a compass). Magnetic bearings need to be corrected for magnetic declination to obtain true bearings.
Important Questions from Compass Surveying and Theodolite
Least count of a theodolite is ________
The meridians that are parallel to the directions taken by freely moving magnetized needles, as in a compass are called as:
For measurement of vertical angles through theodolite, the instrument should be levelled with reference to the ________ bubble and the ________ clamp that is used to rotate the telescope in the vertical plane.
The following statements given pertain to theodolite used in surveying. Identify the incorrect statement
The use of Electronic Digital Theodolite attached to a total station is to measure:
