Traversing is defined as a series of connected lines whose lengths and directions are to be measured and the process of surveying to find such measurements. There are different methods of traversing I have described below.
In general, compass or theodolite are used to measure the direction of traverse lines and chains are used to measure length.
It is a method of establishing control points, their positions being determined by measuring the distances between the traverse stations which are control points, and the angles subtended at the various stations by their adjacent stations.
Depending upon the instrument used in determining the relative directions of the traverse lines, there are four principal methods of traversing:
- Chain traversing
- Compass traversing
- Theodolite traversing
- Plane table traversing
Purpose of Traverse
Brief descriptions of above methods are given below.
Different Methods of traversing
1) Chain traversing
In this method the whole work is done with chain and tape. There is no angle measurement are used and direction of the lines are fined entirely by linear measurements. Angles fixed by linear or tie measurements are called chain angles.
This method is not suitable for accurate work. It is done when an angle measuring instrument is compass or theodolite. The angle between the adjacent traverse lines is measured using the chain angles concept. Chain traversing is performed in areas where it is difficult to adopt triangulation such as ponds.
2) Compass traversing
In compass traversing, both linear and angular measurements of traverse lines are taken by using the chain or prismatic compass respectively. Fore bearing and back bearing are measured and required corrections for local attractions are applied.
If a closing error is obtained while plotting a traverse, then the Bowditch rule is applied for the adjustment of error. There are many types of the compass which is used in traversing are:
3) Theodolite methods of traversing
In this traversing, the linear measurements are done by using chain method and angular measurements are done by theodolite.
The magnetic bearing of the first traverse line is measured by using a theodolite and from that magnetic bearing of other sides is calculated. This method is very accurate as compared to other methods.
4) Plane table traversing
In this methods of traversing, the measuring and plotting of the traverse on the paper and are done simultaneously. The pane table equipment is set at every traverse station one by one in a clockwise or anticlockwise direction.
The sides of each traverse stations are drawn on paper. IF any closing error occurs, then graphical methods are used for its adjustment. It is useful for the following cases:
- It is best fitted for small scale surveying
- It is also used in industrial areas where compass survey fails to perform
- It is used to fill in details between stations fixed by triangulation method or theodolite traversing method.
I hope you got something new about different methods of traversing.
Happy Learning – Civil Concept