Horizontal Angle and Bearings in Surveying

In surveying, horizontal angles and bearings are used to determine the location of points on the earth's surface. A horizontal angle is the angle measured in a horizontal plane between two lines or points. Bearings are used to describe the direction of a survey line or the location of a point with respect to a reference line or direction.

True Bearing

True bearing is the horizontal angle between the true meridian and the survey line measured in a clockwise direction. The true meridian is the line passing through the geographic north and south poles. True bearing is also known as geodetic bearing or astronomical bearing.

Magnetic Bearing

Magnetic bearing is the horizontal angle between the magnetic meridian and the survey line measured in a clockwise direction. The magnetic meridian is the line passing through the magnetic north and south poles. Magnetic bearing is used when magnetic declination is taken into account.

Grid Meridian

Grid meridian is the line passing through the grid north and south poles. Grid north is the direction of the y-axis of a map projection, while grid south is the opposite direction. Grid meridian is used in plane surveying or when using a coordinate system.

Arbitrary Meridian

Arbitrary meridian is any reference line or direction chosen by the surveyor for a particular survey project. It could be a line passing through a prominent landmark, such as a building or a hill, or a line aligned with a particular feature of the landscape.

Conclusion

In surveying, bearings are used to describe the direction of a survey line or the location of a point with respect to a reference line or direction. True bearing is the horizontal angle between the true meridian and the survey line measured in a clockwise direction. The other types of bearings are magnetic bearing, grid meridian, and arbitrary meridian.