1.Kheni Jenil V.2.Chaudhari Bhavin R.3.Navadiya Dharmik V.4.Patel Kevin U.5.Mangukiya Hardik B.

Guided By : Prof. Raval Khushbu Prof. Falguni Soneri

Angular MeasurementCompassBearingMeridian

Basic field operation performed by a surveyor involve linear and angular measurements.

Points on the ground or on map are related to each other through a horizontal distance and a horizontal angle (or direction).

Horizontal angular measurement are made between survey lines to determine the angle between the lines.

A horizontal angle is the difference between two measured directions.

Measurement of horizontal angle is required in traverse surveying and other types of surveying.

A survey line can only be plotted if its length and direction both are known. So, it is necessary to measure linear measurement (length) and angular measurement (direction or horizontal angle) of a survey line.

There are two types of compass.

1.The Prismatic Compass2.The Surveyor’s Compass

1. Cylindrical Metal Box2. Pivot3. Lifting Pin and Lifting Lever4. Magnetic Needle5. Graduated Circle or Ring6. Prism7. Object Vane8. Eye Vane9. Glass Cover10. Sun Glasses11. Reflecting Mirror12. Spring Brake Pin

When the needle of the compass is suspended freely, It always points towards the north. Therefore, all the angles measured with prismatic compass are with respect to north.

While using the compass, it is usually mounted on a light tripod which is having vertical spindle in the ball and socket arrangement to which the compass is screwed. Its working involves following three steps

1.Centering 2.Levelling 3.Focusing

1. Circular Brass box2. Pivot3. Agate Cap4. Magnetic Needle5. Rider6. Glass Cover7. Sight Vane8. Object Vane9. Sliding Piece10. Graduated Circle11. Lifting Lever

When the bearing of a line is measured with respect to magnetic north in clockwise direction it is called magnetic bearing or whole circle bearing.

The value of W.C.B. varies from 0º to 360º.

In this system, the bearing of a survey line is measured with respect to north or south, in clockwise or anticlockwise direction towards east or west.

The value of Q.B. varies from 0º to 90º.

True Bearing : The true bearing of a line is the horizontal angle between the true meridian and the survey line. The true bearing is measured from the true north in the clockwise direction.

Magnetic Bearing : The magnetic bearing of a line is the horizontal angle which the line makes with the magnetic north.

Grid Bearing : The grid bearing of a line is the horizontal angle which the line makes with the grid meridian.

Arbitrary Bearing : The arbitrary bearing of a line is the horizontal angle which the line makes with the arbitrary meridian.

Magnetic Meridian : The direction shown by a freely suspended needle

which is magnetized and balanced properly without influenced by any other factors is known as magnetic meridian.

True Meridian : True meridian is the which passes through the true

north and south. The direction of true meridian at any point can be determined by either observing the bearing of the sun at 12 noon or by sun’s shadow.

Arbitrary Meridian : In case of small works or in places where true

meridian or magnetic meridian cannot be determined, then, any direction of a prominent object is taken as a reference direction called as arbitrary meridian.