1.18.8. Traversing with a Theodolite

Traversing is that type of survey in which a number of connected survey lines form the framework and the directions and lengths of the survey lines are measured with the help of an angle measuring and distance measuring instrument.

Traversing refers to a surveying technique that uses connected survey lines. The survey lines can vary in direction and length, and are typically measured using a theodolite or similar instrument. This method involves determining both the angles between lines and the distances of those lines, allowing surveyors to create an accurate representation of the area being surveyed.

Imagine a person mapping out a new hiking trail in the woods. They walk from point to point, measuring both how far they walk and the angles between the different segments of the trail. Just like they would use a map to connect these locations, a surveyor uses traversing to create a precise map of a land area.

There are two types of traverse surveying: (a) Closed traverse: when the interconnected lines form a closed figure and the last line ends at the beginning of first line, it is known as a closed traverse. The closed traverse is generally used for locating the boundaries of area, lakes, forest, and survey of large areas. (b) Open traverse: when the interconnected lines cover a large area along a corridor, and start point and end point are different and they don’t meet each other, it is said to be an open traverse. The open traverse is preferred for surveying a long narrow strip of land as required for alignment of a road, railway line, canal, etc.

Traversing can be divided into two main categories: closed traverse and open traverse. A closed traverse creates a complete loop, meaning that the last point connects back to the first point, forming a closed shape. This is often used in boundary surveys. On the other hand, an open traverse does not return to the starting point and is typically used to measure long, narrow corridors, such as roads or pipelines. The type of traverse selected depends on the surveying needs.

Consider a team building a new highway. They would use an open traverse to chart the best path for the road, ensuring it is as straight and efficient as possible. Conversely, if they were surveying a park to define its boundaries, they would use a closed traverse to ensure they accurately encircle the entire park.

In theodolite traversing, the field work consists of (i) reconnaissance survey of area, (ii) selection of traverse stations, (iii) marking and locating the traverse stations, (iv) taking observations for traverse lines and angles, (v) adjusting the errors, (vi) computation of coordinates of traverse stations, (vii) plotting the coordinates of traverse stations, and (viii) take more observations of surrounding features to plot them on a map.

The process of traversing with a theodolite involves several key steps: First, conducting a reconnaissance survey to understand the area. Then, selecting and marking the locations of traverse stations where measurements will be taken. Observations for angles and distances are recorded at these stations. After gathering data, any errors in measurements are adjusted for accuracy. Finally, the computed coordinates are plotted and additional features in the area are noted for mapping.

Imagine a chef preparing a new recipe. They first gather all their ingredients (reconnaissance), measure them out precisely (selecting and marking), and adjust as they go along to ensure the dish turns out perfectly (adjusting errors). When they write down the recipe, they are effectively plotting their findings onto a map.

A theodolite is normally used for determining the angles of the traverse lines, and an EDM or tacheometry is commonly used for taking the linear measurements of traverse lines.

During traversing, a theodolite is the main instrument used to measure the angles between the survey lines. This precision instrument excels in capturing accurate angles which define the layout of the traverse. For measuring distances, Electrical Distance Measurement (EDM) or tacheometry is used, providing efficient and accurate linear measurements necessary for the calculations involved in traversing.

Think of a photographer using a camera (theodolite) to capture angles for a shot, while a ruler (EDM) helps them measure the distance to ensure the perfect composition. Each tool serves a specific yet complementary purpose in achieving the desired result.

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