Difference Between Closed Traverse and Open Traverse in Surveying

Difference Between Closed Traverse and Open Traverse in Surveying

In surveying, traversing refers to the process of measuring a series of connected lines for their lengths and directions. There are two main types of traverses: closed traverse and open traverse. A closed traverse forms a closed circuit, starting and ending at the same point or at two known points.

This type of traverse is commonly used for surveying boundaries of ponds, forests, and sports grounds. The accuracy of a closed traverse can be assessed by summing the interior angles of the polygon formed by the traverse, allowing for error distribution and calculations.

On the other hand, an open traverse starts at one point and ends at another, without forming a closed circuit. Open traverses are suitable for surveying long narrow strips of land, such as roads or coastlines. However, unlike closed traverses, open traverses cannot be assessed or corrected for errors in the same way.

Repeated measurements of angles and distances are necessary to assess the accuracy of open traverses, which can be costly and time-consuming. Both closed and open traverses have their own applications and considerations in surveying, and the choice between them depends on the specific requirements of the survey.

Key Takeaways:

• A closed traverse forms a closed circuit, while an open traverse does not.
• Closed traverses are used for surveying boundaries, while open traverses are used for long narrow strips of land.
• Closed traverses can be evaluated by summing interior angles, while open traverses require repeated measurements.
• Closed traverses allow for error calculations, while open traverses do not have direct error checks.
• Both closed and open traverses have their own advantages and suitability for different types of surveys.

Types of Traverse in Surveying

In surveying, traverses are categorized into two main types – open traverse and closed traverse. An open traverse starts at one point and terminates at another point, without forming a closed circuit. It is suitable for surveying long narrow strips of land, such as roads or coastlines.

On the other hand, a closed traverse forms a closed circuit, with the starting and ending points of the traverse coinciding. It is commonly used for surveying large areas and locating the boundaries of lakes, forests, and other features. Closed traverses allow for the quantification of measurement errors by summing the interior angles of the polygon formed by the traverse.

In open traverse, the surveyor follows a series of straight lines, measuring both their lengths and directions. The traverse does not form a closed circuit, so the accuracy of the measurements cannot be assessed by summing the interior angles.

Instead, repeated measurements of angles and distances are necessary to evaluate the accuracy of the traverse. Due to the costly nature of repeated measurements, open traverses are typically used for less critical applications, where a higher degree of accuracy is not required.

In closed traverse, the surveyor also measures the lengths and directions of the traverse lines. However, the traverse forms a closed circuit, starting and ending at the same point or at two known points. This allows for the evaluation of measurement errors by summing the interior angles of the polygon formed by the traverse.

By comparing the sum of interior angles with the expected value, the surveyor can identify and distribute any errors. Closed traverses are commonly used for surveying boundaries of ponds, forests, and sports grounds, where accuracy is crucial.

Overall, the choice between open and closed traverse depends on the specific surveying requirements. Open traverses are suitable for surveying long narrow strips of land, while closed traverses are preferred for surveying large areas and locating boundaries. The selection of the appropriate traverse type ensures accurate and reliable surveying results.

Key Points:

• Open traverse starts at one point and ends at another, without forming a closed circuit.
• Closed traverse forms a closed circuit, allowing for the assessment of measurement errors.
• Repeated measurements are required for evaluating the accuracy of open traverses.
• Closed traverses are commonly used for surveying boundaries of ponds, forests, and sports grounds.
• The choice between open and closed traverse depends on the specific surveying requirements.

	Open Traverse	Closed Traverse
Definition	A traverse that does not form a closed circuit	A traverse that forms a closed circuit
Application	Suitable for surveying long narrow strips of land	Used for surveying large areas and locating boundaries
Evaluation of Accuracy	Requires repeated measurements of angles and distances	Assessed by summing the interior angles of the polygon formed by the traverse
Common Uses	Surveying roads, coastlines, and other linear features	Surveying boundaries of ponds, forests, and sports grounds

Methods of Traversing in Surveying

Traversing in surveying involves various methods for measuring the lengths and directions of traverse lines. These methods utilize different survey instruments depending on the specific requirements of the survey. The four main methods of traversing are:

• Chain Traversing: This method involves measuring linear distances using a chain or tape. It is a simple and straightforward technique that is commonly used for shorter survey lines.
• Compass Traversing: Compass traversing combines linear and angular measurements using a prismatic compass and chain. It is suitable for surveys that require both distance and direction measurements.
• Theodolite Traversing: Theodolite traversing utilizes a theodolite, which is a precision instrument for measuring angles. Angular measurements are taken using the theodolite, while linear measurements can be made using either a chain or the stadia method.
• Plane Table Traversing: Plane table traversing involves simultaneous measurement and plotting on a plane table. This method allows for quick and efficient surveying, as measurements are directly plotted on the table.

Each method has its own advantages and suitability depending on the specific requirements of the survey. For example, chain traversing is often used for shorter distances, while theodolite traversing offers precise angular measurements. It is important to consider factors such as accuracy, terrain, and the availability of equipment when selecting the appropriate method for a survey.

“Theodolite traversing offers precise angular measurements, making it suitable for surveys that require high accuracy.”

By understanding these different traversing methods, surveyors can choose the most suitable technique for their specific surveying needs, ensuring accurate and reliable results.

Comparison of Traversing Methods

Method	Advantages	Disadvantages
Chain Traversing	Simple and straightforward	Less precise compared to other methods
Compass Traversing	Combines distance and direction measurements	Susceptible to magnetic interference
Theodolite Traversing	Precise angular measurements	Requires additional equipment
Plane Table Traversing	Simultaneous measurement and plotting	May be less accurate for larger surveys

Note: The table above provides a comparison of the different traversing methods. It highlights the advantages and disadvantages of each method, allowing surveyors to make informed decisions based on their specific project requirements.

Errors in Traversing and Traverse Computation

Traversing in surveying is a precise process, but it is not without errors. Two main types of errors that can occur are linear error and angular error. Linear errors refer to inconsistencies in the measured lengths of traverse lines, while angular errors pertain to discrepancies in the measured angles of the traverse.

To check for linear error, it is recommended to chain each survey line a second time, preferably in the reverse direction. This allows for the assessment of measurement consistency and helps identify any potential errors. On the other hand, angular error checks differ depending on the type of traverse.

For closed traverses, one common check involves verifying that the sum of measured interior angles equals (2N-4), where N is the number of sides of the traverse. This check ensures that the traverse has been accurately measured and closed. However, for open traverses, there are no direct checks to verify the accuracy of angular measurements.

Traverse computations play a crucial role in the surveying process. They involve calculating the lengths and angles of traverse lines and plotting the traverse on paper using methods such as angles and distance or co-ordinate method.

These computations help in visualizing and representing the traverse accurately. By incorporating these computations, surveyors can identify any errors and make necessary adjustments to ensure the accuracy of their survey data.