1.18.9. Methods of theodolite traversing

The measurement of angles between two successive lines is generally carried out for large traverses where the high degree of accuracy is required. In this method, the angles between the successive lines are measured, and the bearing of a line is observed. The bearings of the remaining lines can be computed from the observed bearing and angles.

Theodolite traversing involves measuring angles between various lines in a survey to ensure accuracy. When conducting a land survey, especially over large areas, ensuring that your measurements are accurate is crucial. To achieve this, surveyors use a theodolite to measure the angles between consecutive lines accurately.

Think of it like navigating a detailed map of a large theme park. Each angle you take at intersections helps you determine the paths you’ll follow next, ensuring you reach your desired attractions without getting lost.

In a closed traverse, the angles measured are either exterior or interior, accordingly the traverse is run in a clockwise direction or in anti-clockwise direction. The sum of the two angles (exterior and interior) at a traverse station is 3600.

A closed traverse is a surveying method where the final point connects back to the starting point, forming a closed shape. This is important as it allows for a checked measurement, ensuring that any errors can be identified. Whether measuring interior or exterior angles, the total will always amount to 360 degrees at each station. This method helps verify the correctness of all calculated values in the survey.

Imagine you are taking a walk around a city block and return to your starting point. If you correctly measure your turns (angles) throughout your walk, you can ensure you don't end up farther away when you thought you were close to home!

The angles can be measured by the method of repetition for greater precision. The distance between traverse sides is determined either by tacheometry (if it is short) or EDM/Total Station (if it is long). The closed traverse is preferably run in anti-clockwise direction.

The method of repetition involves measuring the same angle multiple times to improve accuracy. This helps compensate for any potential human or instrument errors. The distances in a closed traverse can be recorded using tacheometry for shorter distances or an EDM for longer stretches. Typically, the survey is performed in an anti-clockwise direction for consistency in measurements.

Consider baking a cake where you need to measure your ingredients precisely. If you accidentally add too much sugar, going back and measuring accurately each time ensures your final product is sweetened exactly as intended.

In case of an open traverse, deflection angle is measured. Deflection angle is the angle made by a traverse line with the extended preceding traverse line.

An open traverse represents a survey where the starting and ending points do not meet. Instead of measuring angles that return you to start, here, you assess how each new line deviates from the previous one. This is done using deflection angles, which indicate how much a line turns from the previously established line. These angles are essential in aligning roads or pipelines where straight paths may need to bend.

Think of driving on a winding road. Each turn (deflection angle) that veers left or right from your initial path helps you navigate towards your destination, ensuring you stay on the correct route without backtracking.

In running a traverse, set up the theodolite at the starting station A and observe the bearing of line AB. Then shift the instrument to station B, set the vernier A reading to zero and take a back sight reading on A.

When performing an open traverse, the theodolite is positioned at the starting point to measure the initial line (bearing). Once established, the surveyor shifts the equipment to the next point and measures the angle relative to a reference point. This process allows for tracking how the survey line deviates from previously set paths, ensuring a continuous and correct measurement.

Imagine you are following a treasure map that leads from point to point. At each marker, you take careful note of where you’ve been (the bearing) so that when you move to the next point, you can accurately continue your treasure hunt without losing your way.

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