What is WCB and RB in surveying
Whole Circle Bearing and Reduced Bearing
What is WCB and RB in Surveying
(WCB) Whole circle bearing
In the WCB, bearings are measured from north of the reference meridian.
These bearings are lie between 0° to 360° in the clockwise direction. In the prismatic compass Surveying, we use the whole Circle bearings. WCB is also referred to the Azimuthal bearing system.
In the whole circle bearing ( W.C.B ) the bearing of a line at any point is the measured with respect to a meridian. It is the value varies from 0 to 360°, increasing in the clockwise direction. Zero is north direction, 90° is east, 180° is south and 270° is west ( Ref. Fig. 13.2 ). This type of the bearing is used in prismatic compass.
In the reduced bearing ( R.B ) system, the bearings are measured from north or south direction towards east or west. Hence, angles are from Zero to 90° as shown in Fig. 13.3. This system of the measuring bearings is used in the Surveyors compass & it is also known as Quadrantal Bearing ( Q. B ). The bearing measured is designated with letter N or S in the beginning to indicate whether it is from the north or south. The letter E or W written after the angle indicates whether the bearing read is towards east or west, respectively.
In the WCB system is,
North = 0°
East = 90°
South = 180°
West = 270°
In the WCB, line AB is measured at 52° from North as shown below.
Similarly, the line BC is measured at 285° from north as shown in the below drawing.
To understand A to Z of the Surveying,
(RB) Reduced bearing
In the RB, bearings are measured from north or south, either in a clockwise or anticlockwise directions. The reading is taken depending upon the quadrantal positioning of line.
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In this system, the bearing is referred to by four possible quadrants i.e. NE, NW, SE, and SW. Therefore this system is also called quadrantal bearing.
The angles in RB system lie between 0° to 90°.
In the Surveyor’s compass, we used the RB system.
1. Line A&B lies in the NW quadrant i.e. fourth quadrant. This line is nearer to the north line and away from the south line. So, the angle is measured in an anti-clockwise direction from N line.
To understand the position of line A&B, the measured angle is denoted as ( N34°W )
2. The line A&B lies in the NE quadrant i.e. First quadrant. This line is nearer the N line and away from the south line. So, the angle is measured in a clockwise direction from the N (north) line.
To understand the position of line A&B, the measured angle is denoted as ( N55°15’E)
3. The line A&B lies in the SE quadrant i.e. Second quadrant. This line is nearer to the south line and away from the north line. So, the angle is measured in an anti-clockwise direction from the S( south) line.
To understand the position of line A&B, the measured angle is the denoted as ( S67°45’E )
4. The line A&B lies in the SW quadrant i.e. Third quadrant. This line is nearer to the south line and away from the N ( north ) line. So, the angle is measured in a clockwise direction from the S ( south ) line.
To understand the position of line A&B, the measured angle is the denoted as NS42°W
From above eg., you can observe that the angles in the First and Fourth quadrants are measured with reference to the north and angles in the Second and Third quadrants are measured from the S (south).
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