Traversing in Surveying

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Traversing in Surveying

Traversing in surveying is a fundamental technique used to determine the location of points on the Earth’s surface.

It involves the process of measuring distances, directions, and elevations between various points to create a map or plan of a specific area. This technique has been used for centuries to aid in the development of cities, infrastructure, and other important construction projects.

In this article, we will explore the basics of traversing, its history, and its modern-day applications in the field of surveying.

Objectives of Traversing in Surveying

The primary objective of traversing in surveying is to determine and establish accurate and precise horizontal and vertical control points on the ground.

This involves a series of interconnected survey lines, which are measured and observed to determine the relative positions and angles of these control points.

The specific objectives of traversing in surveying are as follows:

1. Establishing Control Points:

Traversing allows for the efficient and accurate establishment of control points that serve as a framework for subsequent surveys. These control points provide a stable base of reference for all future surveys and construction projects in the vicinity.

2. Determining Horizontal and Vertical Positions:

Traversing is an essential technique for determining the horizontal and vertical positions of points on the ground. By measuring the angles and distances between control points, the exact locations of features, boundaries, and other points of interest can be determined.

3. Creating Accurate Maps and Plans:

Traversing is a fundamental component of map-making and plan drawing. By accurately establishing control points and determining positions, traversing enables the creation of precise maps and plans that are essential for various purposes such as land development, infrastructure planning, and resource management.

4. Establishing Property Boundaries:

Traversing is often used in property surveys to determine the exact boundaries of land parcels. This is crucial for legal purposes, as well as for avoiding disputes between adjoining property owners.

5. Providing Topographic Data:

Traversing allows for the collection of topographic data, which is necessary for understanding the shape and features of the land. This information is useful for various applications, including engineering design, environmental studies, and land use planning.

6. Controlling Construction:

Traversing plays a vital role in construction projects by providing accurate and precise control points that guide building and infrastructure construction. This ensures that structures are built in the correct locations and according to the designed specifications.

Types of Traverse in Surveying

A traverse in surveying refers to a series of interconnected lines or boundary measurements used to determine the position of points on the ground in relation to each other.

This technique is essential in civil engineering, as it helps to establish the accurate location and direction of structures and other features within a project site.

There are several types of traverses used in surveying, and each has its own unique characteristics and applications. Some of the common types of traverse used in surveying are described below:

1) Closed Traverse:

This type of traverse consists of a series of interconnected lines that form a closed loop. It starts and ends at the same point, and all the lines are measured and computed in a clockwise or anticlockwise direction. Closed traverses are commonly used in topographical surveys to determine the boundaries of a project site or to establish the location of existing features.

2) Open Traverse:

Unlike a closed traverse, an open traverse does not form a closed loop but has a starting and end point that are different. It involves a series of interconnected lines, with the final point not necessarily connected to the initial point. Open traverses are useful in surveys that include large areas and need to be divided into smaller sections for easier measurement and computation.

3) Compound Traverse:

A compound traverse consists of two or more closed traverses that are interconnected at one or more points. Its primary purpose is to ensure the accuracy of the surveyed data by reducing the chances of error. Compound traverses are typically used in complex surveys that require a high level of precision.

4) Straight Line Traverse:

As the name suggests, this type of traverse involves a series of connected straight lines. This can be done by using a calibrated tape or a total station instrument. The distance between the points, as well as the angles between the lines, are measured and recorded to create an accurate map or plan of the survey area.

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5) Polygonal Traverse:

This type of traverse is similar to a closed traverse, but it involves a series of interconnected straight lines forming a polygonal shape. It is useful for surveys that involve irregular-shaped areas and requires more control points for better accuracy.

6) Radial Traverse:

A radial traverse is used to determine the position of points from a central point by using a set of known bearings and distances. This type of traverse is beneficial in surveys that involve circular or curved boundaries, such as for construction of roads, railways, or pipelines.

Balancing The Traverse

As a civil engineer, it is my responsibility to ensure that structures are designed and constructed to be safe and functional for their intended purpose. One important aspect that requires careful attention is the balance of a traverse.

A traverse is a series of connected points measured in the field to determine the horizontal and vertical locations of objects such as roads, pipelines, and buildings. It is a crucial part of the surveying process and forms the basis for the design of any project.

Achieving balance in a traverse is essential as it ensures the accuracy and reliability of the measurements. This balance is achieved by the careful adjustment of the survey data using a technique called “adjustment of observations.” This process involves identifying and correcting any errors or inconsistencies in the measurements.

The first step in balancing a traverse is to compute the closures in both horizontal and vertical directions.

Closure is the difference between the starting and ending points of the traverse. A perfectly balanced traverse will have zero closures in both horizontal and vertical directions.

If the closures are not zero, it indicates that there are errors in the measurements, and adjustments need to be made. The adjustments are made by altering the coordinates of a few points in the traverse to minimize the closure errors.

To achieve balance in the traverse, it is crucial to follow a systematic approach and ensure that all the errors are identified and removed.

This involves carefully inspecting the field notes, checking for any possible sources of errors, and applying appropriate corrections. The most common types of errors in a traverse include measurement errors, incorrect angles, incorrect distances, and errors in the instrument.

Once the adjustments are made, the traverse is re-balanced, and the closures are re-computed. This process is repeated until the closures are within an acceptable range. Achieving a balanced traverse provides a reliable basis for the design and construction of structures.

Adjustment of Angular Error and Bearing

Physical Surveying

Adjustment of Angular Error and Bearing in Physical Surveying

In physical surveying, it is crucial to have accurate angular measurements and bearings in order to ensure the precision and reliability of the survey data. However, due to various factors such as instrument errors, environmental conditions, and human errors, it is inevitable that some angular errors may occur.

Therefore, the adjustment of angular error and bearing is necessary to correct these errors and obtain reliable survey data.

Angular error refers to the difference between the measured angle and the true angle. It can be caused by a number of factors, including imperfections in the surveying instrument, improper leveling, and human error in reading the instrument.

The first step in adjusting angular error is to identify the source of the error. This can be done by performing a series of redundant measurements using different methods and instruments and comparing the results.

Once the source of the error is determined, the next step is to apply the appropriate correction methods.

Common correction methods include balancing the angle, adjusting the collimation error, and utilizing the least square method. Balancing the angle involves measuring the same angle from two different points and taking the average of the two readings.

This helps to minimize the effect of any instrumental or leveling errors. Adjusting the collimation error involves correcting the horizontal and vertical alignment of the instrument. This can be achieved through fine-tuning the screws or using a collimation device.

The least square method is a mathematical technique that can be used to minimize the effects of random errors. It involves carrying out multiple measurements and determining the most probable value for the angle.

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This method is particularly useful when dealing with a large number of measurements.

Bearing is the direction that a line or a point is measured in relation to a reference direction, usually the north-south axis.

It is crucial to have accurate bearings in a survey as they form the basis for establishing the orientation and location of all other features in the surveyed area.

A compass or a theodolite is used to record bearings in a physical survey. However, these instruments are not always free from errors, and it is important to adjust these errors to obtain reliable bearings.

Pre-adjustment methods, such as balancing the angle and adjusting for local attraction, can help minimize errors before recording bearings. Post-adjustment methods, such as graphical and computational methods, can be used to further refine and adjust the bearings.

Discrepancy and Linear Mis-closure

As a civil engineer, it is my responsibility to ensure the accuracy and precision of any project I am involved in. This means thoroughly checking all measurements and calculations to identify any discrepancies or linear mis-closures.

Discrepancy refers to a difference or inconsistency between two or more values or sets of data. In the context of civil engineering, this could occur during the construction phase when actual measurements do not align with the initial design plans. This could be due to mistakes in measurements, errors in calculation, or unforeseen site conditions.

In order to address discrepancies, it is important to conduct regular site inspections and compare the as-built measurements with the design plans.

Any discrepancies should be identified and investigated to determine the cause and remedial actions should be taken to ensure the project meets the required standards.

Linear mis-closure, on the other hand, refers to the difference between the initial and final measurements along a linear traverse.

This typically occurs during surveying activities and can result from various factors such as measurement errors, instrument malfunctions, or inadequate survey techniques.

To minimize linear mis-closures, strict surveying protocols should be followed, and the use of advanced surveying equipment, such as electronic measurement devices, should be employed.

Regular checks and adjustments should also be made during the surveying process to ensure accuracy.

Methods of Traversing in Surveying

Traversing is an essential technique used in surveying to establish the relative position of points on the ground. It involves taking a series of linear and angular measurements to determine the distances and directions between points and to create a closed polygon. There are several methods of traversing in surveying, each with its advantages and limitations. In this article, we will discuss the most commonly used methods of traversing.

1. Closed Traverse Method:

The closed traverse method is the most basic and widely used method of traversing. It involves measuring the distances and angles between consecutive points, starting from a known benchmark and ending at the same point.

This creates a closed polygon, and the sum of the interior angles should be equal to 360 degrees for an accurate traverse. This method is relatively simple and is suitable for small-scale surveys.

2. Open Traverse Method:

The open traverse method is similar to the closed traverse method, except the starting and ending points are not the same. This method is useful when the area to be surveyed is too large to close a polygon and requires multiple traverses. The open traverse is closed by taking fore and back bearings at the last point and adjusting the last line until the difference between the two bearings is within an acceptable limit.

3. Transit Traverse Method:

The transit traverse method uses a transit or theodolite to measure both horizontal and vertical angles to determine the position of points. This method is more accurate than the plane table traverse as it eliminates the errors caused by magnetic needle oscillation. It is suitable for large-scale surveys, especially in areas with rugged terrain.

4. Compass Traverse Method:

The compass traverse method uses a magnetic compass to determine the angles between points and measure the distance using a chain or tape. This method is simple and does not require any specialized equipment; however, it is prone to errors due to magnetic declination and local attraction. It is suitable for small-scale surveys on a level and open ground.

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5. GPS Traverse Method:

With advances in technology, the GPS (Global Positioning System) has become an essential tool in surveying. The GPS traverse method uses satellite signals to determine the precise position and elevation of points. This method is highly accurate and efficient, making it suitable for large-scale surveys or complex terrains.

Conclusion

In conclusion, traversing in surveying is a fundamental technique used to establish accurate measurements and create precise maps and plans. It involves a systematic process of measuring angles and distances between points, and is essential in various industries such as construction, engineering, and land development. By understanding the principles and methods of traversing, surveyors can ensure the reliability and consistency of their survey data, leading to efficient and successful projects. With advancements in technology, the traditional methods of traversing may have been replaced by modern equipment, but the fundamental principles remain the same. Therefore, it is important for surveyors to continuously enhance their skills and knowledge in traversing to maintain the quality and integrity of surveying work. Overall, traversing continues to play a crucial role.


Frequently Asked Questions (FAQs) – Traversing in Surveying

1. What is traversing in surveying, and why is it considered a fundamental technique?

Traversing in surveying is a fundamental technique used to determine the location of points on the Earth’s surface. It involves measuring distances, directions, and elevations between various points to create a map or plan of a specific area. It has been used for centuries to aid in the development of cities, infrastructure, and other construction projects.

2. What are the primary objectives of traversing in surveying?

The primary objectives of traversing include establishing accurate horizontal and vertical control points on the ground, determining horizontal and vertical positions of points, creating accurate maps and plans, establishing property boundaries, providing topographic data, and controlling construction.

3. Can you explain the types of traverses used in surveying?

Certainly. There are several types of traverses in surveying, including closed traverse, open traverse, compound traverse, straight line traverse, polygonal traverse, and radial traverse. Each type serves different purposes and has unique characteristics.

4. What is the significance of balancing a traverse in surveying?

Balancing a traverse is essential to ensure the accuracy and reliability of measurements. It involves adjusting survey data to minimize closure errors, ensuring that the starting and ending points of the traverse align. This is crucial for the design and construction of structures.

5. How is angular error adjusted in physical surveying?

Angular error, the difference between measured and true angles, can be adjusted by methods such as balancing the angle, adjusting collimation error, and utilizing the least square method. These techniques help correct errors caused by imperfections in surveying instruments and environmental conditions.

6. What are the common types of traversing methods used in surveying?

Common traversing methods include closed traverse, open traverse, transit traverse, compass traverse, and GPS traverse. Each method has its advantages and limitations, making them suitable for different surveying scenarios.

7. What is the significance of discrepancy and linear mis-closure in civil engineering projects?

Discrepancy refers to differences between measured and expected values, and linear mis-closure involves differences in linear traverse measurements. Identifying and addressing these issues is crucial during site inspections to ensure project accuracy and compliance with design plans.

8. How has technology, specifically GPS, influenced traversing in modern surveying practices?

With technological advances, GPS has become a vital tool in surveying. The GPS traverse method utilizes satellite signals for precise positioning and elevation determination, offering high accuracy and efficiency, especially in large-scale surveys or complex terrains.

9. Why is traversing considered a fundamental technique despite technological advancements?

While technology has introduced modern equipment like GPS, the fundamental principles of traversing remain crucial. Understanding angles, distances, and systematic measurement processes ensures the reliability of survey data, contributing to the success of construction and development projects.

10. How can surveyors continuously enhance their skills and knowledge in traversing?

Surveyors can stay updated on industry advancements, participate in training programs, and leverage technological resources. Continuous learning and practice are essential for maintaining the quality and integrity of surveying work in the evolving field of traversing.

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