Traversing in surveying: Types and purpose

A traverse is a collection of connected lines whose lengths and directions are to be measured. Traversing is the process of surveying to find these measurements. In general, traverse lines are measured for length using chains, and their direction is measured using a theodolite or compass.

Main purpose of traversing

In the field of surveying, traversing is a technique used to create control networks. Additionally, geodetic work employs it. In traverse networks, the survey stations were placed along a line as well as the path of travel, and the originally surveyed points served as a base for the observation of the following point.

Different types of traverses

There are two types of traverses namely, open traverse and closed traverse.

Open traversing

When a traverse begins at one point and ends at another it is said to be an open traverse. Unclosed traverse is another name for the open traverse. It is ideal for measuring things like coastal lines and road lengths.

Closed traversing

When a traverse creates a closed circuit it is said to be a closed traverse. In this instance, the traverse’s beginning and end points are in exact alignment. It is appropriate for conducting boundary surveys for ponds, sports fields, forests, etc.

Different methods of traversing

Four different techniques are used to perform traversing, and each technique is categorised based on the survey instrument that was employed. These are the techniques.

Chain traversing

Only linear measurements can be taken during chain traversing. So, for chain traversing, chain or tape will do. The chain angles concept is used to calculate the angle between both the adjacent traverse lines. Where triangulation is challenging to implement, chain traversing is used in places like ponds and other bodies of water.

Finding the angle of the two adjacent sides by creating a third side using tie stations is the basic idea behind chain angles. By creating a chord between the sides that is a known length, this angle between both sides can also be fixed.

Compass traversing

In compass traversing, the traverse lines are measured both linearly and angularly using chain and prismatic compasses, respectively. Back and forward bearings are measured, and any necessary adjustments for local attraction are made. When plotting a traverse, if a closing error occurs, the Bowditch rule is used to correct the error.

Theodolite traversing

In the case of theodolite traversing, the chain or stadia method is used for linear measurements while theodolite is used for angular measurements. The permanent magnet bearing of the first traverse connection is measured using a theodolite, and other sides’ magnetic bearings are calculated using that measurement. Compared to other methods, this one is very accurate.

Plane table traversing

When traversing a plane table, measurements are taken concurrently with plotting the traverse on paper. At each traverse station, the plane table device is set up one by one in either a clockwise or anticlockwise direction. On paper, the edges of each traverse station are depicted to scale. The correction of any closing errors is done using graphical methods.

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