Reduced Bearing (RB) / Quadrantal Bearing (QB) | Surveying
In Quadrantal bearing (QB) / Reduced bearing (RB) - Bearings are measured either clockwise/anti-clockwise from north/south whichever is close to the line.
Bearing system is of two types - Whole circle bearing and reduced bearing. First let us understand what is meant by bearing and meridians.
Bearing and Meridians
Bearing of line : Direction with respect to a given meridian
Meridian is a fixed reference line
Types of meridian and bearing
True Meridian - Line through true north and south poles, and this remains constant throughout. To find out this line, we need astronomical observations.
Bearing with respect to true meridian is known as true bearing
Magnetic Meridian - Direction indicated by freely suspended magnetic needle, and this magnetic N-S line changes with location and time as they are affected by earth’s magnetism.
Bearing with respect to magnetic meridian is known as magnetic bearing.
Arbitrary Meridian - Well defined reference object like a tower whose position is not going to change, directions are measured with respect to it and they are known as arbitrary bearings
Reduced Bearing (RB) / Quadrantal Bearing (QB)
Bearings are measured either clockwise/anti-clockwise from north/south whichever is close to the line.
Angles vary from 0 degrees to 90 degrees
It is measured from either clockwise/anti-clockwise from north/south (If the line is closer to south and going towards west, it is read as Sβ°W)
Four quadrants are possible namely NE, SE, SW and NW
Surveyor's compass used RB system
In the figure below, the line lies closer to south line (and towards west) - in the third quadrant.
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