Surveying is a branch of civil engineering which determines the relative position of points on the earth. Traverse surveying is a type of surveying in which we connect the survey lines to form a framework. The length of survey lines is calculated using an angle measuring instrument and a tape. Some important traversing methods are Chain traversing, Chain and compass traversing, Tape traversing, and plane table traversing. In this article, we are going to deal with traverse surveying, types of traverse, and methods of traverse.
What is Traverse Surveying?
Traverse surveying is a process of surveying in which we establish a series of straight lines and measure their length and direction. For measuring the length we use instruments like chains or tapes and for calculating the direction we use instruments like a theodolite, plane table, compass. Each point through which the lines passes are known as a traverse station. We can determine the length of lines by two methods namely direct or indirect measurement method. The main purpose of traverse surveying are
- To establish the boundary points.
- To determine the position of existing boundary points.
- For calculating the area within boundary points.
- To establish layouts for the preparation of maps.
- To determine the data necessary for the construction of highways, roadways and other construction works.
Types of Traverse
There are mainly two types of traversing.
- Open traverse
- Closed traverse
Open traverse
Another name of open traverse is first-class traverse. The first point of this traverse is the point of which its position is known with respect to the horizontal datum. This traverse ends without closure. This traverse method is applicable for the construction of highways, railways, pipelines, etc. To reduce errors, we should repeat the measurements in an open traverse.
Closed traverse
Another name of closed traverse is second class traverse or loop traverse. In this type of traverse, it starts from a point where its position is known and ends at the same point. We can determine the position and angle between the points mathematically. This traverse is more accurate than an open traverse
Method of traversing surveying
On the basis of the instruments, there are several methods of traversing. They are
- Chain traversing
- Plane table traversing
- Compass traversing
- Theodolite traversing
Chain traversing
In this type of traversing, we use instruments like chains and taps for the measurement of length. We do not measure angles in chain traversing. We determine the direction of lines by linear measurements. This traversing is suitable in places that have ponds or streams, It is inaccurate.
Plane table traversing
In-plane table traversing, we plot the traverse on paper. In this type of traversing, we set up the plane table at each station and each traverse line is drawn on paper. It is the quickest and easiest method of traversing.
Compass traversing
In this type of traverse surveying, we determine both the linear and angular measurements using a chain and compass. Using the compass we measure the forbearing and back bearing. Since we use a compass in all stations, due to local attractions there are chances of error occurrence. Therefore they are not accurate.
Theodolite traversing
In this method of traversing, we measure the angles by using a theodolite and for linear measurements we use chains. It is one of the precise methods of traversing.