Short Answer

Compass surveying in civil engineering is a method of surveying in which directions (angles) of survey lines are measured using a compass along with linear measurements. It is mainly used to find the magnetic bearing of lines and prepare maps of an area.

In compass surveying, both distance and direction are recorded to fix the position of points on the ground. It is useful for large or rough areas where chain surveying is difficult. It provides moderate accuracy and is widely used in preliminary surveys.

Detailed Explanation:

Compass surveying basics

Compass surveying in civil engineering is a type of surveying in which the direction of survey lines is determined using a compass, and the distances are measured using a chain or tape. It is used to prepare maps and plans of an area by measuring both distance and direction together.

In this method, the main instrument used is the compass, which helps in measuring the magnetic bearing of survey lines. The magnetic bearing is the angle between a survey line and the magnetic north direction. This makes it possible to locate points accurately on the ground.

Compass surveying is commonly used for large areas where chain surveying alone is not suitable due to obstacles, uneven ground, or long distances.

Instruments used in compass surveying

The main instrument used is the compass, which is used to measure directions. The two commonly used types are the prismatic compass and the surveyor’s compass.

Other instruments include chain or tape for measuring distances, ranging rods for marking survey points, arrows for counting chain lengths, and pegs for fixing stations on the ground.

All these instruments work together to measure both direction and distance accurately in the field.

Working method of compass surveying

In compass surveying, the area is divided into a series of connected survey lines. Each line has a starting point and an ending point. The direction of each line is measured using a compass, and the distance is measured using a chain or tape.

The surveyor stands at one point and observes the next point using the compass to find its bearing. Then the distance between the two points is measured. This process is repeated for all survey lines.

The collected data is recorded in a field book, which is later used to draw a map of the area.

Compass surveying is based on the principle of traversing, where a series of connected lines form a closed or open loop.

Types of compass surveying

There are mainly two types of compass surveying: open traverse and closed traverse.

Open traverse

In open traverse, the survey starts at one point and ends at another point that is not connected back to the starting point. It is used for road, railway, and canal surveys.

Closed traverse

In closed traverse, the survey lines form a closed loop and end at the starting point. It is used for boundary surveys and area measurement.

Closed traverse is more accurate because errors can be easily checked and adjusted.

Advantages of compass surveying

Compass surveying is simple and easy to perform in the field. It is useful for large and rough areas where chain surveying is difficult.

It requires less time and can cover large areas quickly. It is also useful in preliminary surveys where detailed accuracy is not required.

It helps in measuring both direction and distance together, making it more efficient than simple chain surveying.

Limitations of compass surveying

Compass surveying has some limitations. It is affected by local magnetic fields, which can cause errors in direction measurement.

It provides only moderate accuracy and is not suitable for very precise engineering work. It can also be affected by nearby metal objects and electrical interference.

Because of these limitations, it is often used only for preliminary or rough surveys.

Conclusion

Compass surveying in civil engineering is a method that uses a compass to measure directions and a chain or tape to measure distances. It is useful for large areas and preliminary surveys. Although it has some limitations, it is simple, fast, and widely used in field surveying work.