A traverse survey is a type of control survey which involves the establishment of a series of points that are linked together by lines to form a framework. The series of straight lines that connect the successive points are called traverse lines. The ends that defined each traverse line are called traverse stations or traverse points. The framework formed by connected survey lines of known length and direction is called a traverse.

Image Courtesy: Braincart |

In the figure-1 below, A,B,C and D are traverse stations. AB, BC, and CD are traverse lines.

Fig.1. Traverse Survey |

In traversing, the surveyor move from one point to other by simultaneously measuring bearings and distances by "dead reckoning". Dead reckoning is the process of calculating current position of some moving object by using a previously determined position. Employed when the construction work is long and narrow ( tunnel or motorway construction).

### Scope and Objective of Traverse Survey

Traverse survey is conducted to establish horizontal control in land areas especially in areas where the line of sights (LOS) are short due to heavy built-up areas, where the survey methods triangulation and trilateration are not applicable.

The main objective of traverse survey are:

- To locate or establish boundaries
- To achieve horizontal control for topographic surveys
- To locate and prepare construction layout for highways, railways, and other private and public works
- To conduct ground control surveys for photogrammetric surveys

### Types of Traverse

The two types of traverse encountered while conducting surveys are:

- Open Traverse
- Closed Traverse

#### 1. Open Traverse

Fig.2. Types of Traverse - Open and Closed Traverse |

The consistence of angles and distance measured cannot be checked in open traverse. So, in order to minimize the errors, the distances can be measured twice, angles turned by repetition, etc.

#### 2. Closed Traverse

### How are Traverse Lines Measured?

The traverse lines is either determined by:

- Direct measurement : Tapes, EDM
- Indirect measurement: Tachometric Methods
- Angular measurement : Theodolite

### Different Methods of Traversing in Surveying

- Chain Traversing
- Compass Traversing
- Interior angle traverse
- Theodolite Traversing
- Deflection angle traverse
- Angle to the right traverse
- Azimuth traverse
- Stadia Traversing
- Plane table and alidade Traversing

What is the Procedure to Perform Traverse Survey?

- Reconnaissance
- Selection of Traverse Stations
- Linear and Angular Measurements

__Step 1: Reconnaissance__

- The surveyor go to the field and check the entire area.
- He decides the best plan of working.
- He checks the intervisibility of the traverse stations
- He decides the method of traversing to be adopted
- Based on the method chosen, the instruments and accessories are selected accordingly.

__Step 2: Selection of Traverse Stations__

- A minimum number of traverse stations should be selected.
- Take the length of the traverse line as long as possible to reduce the time and centering effect of stations.
- Try to select stations on a level and firm ground
- After selecting the stations, mark them using pegs.