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Chain Surveying

Chain surveying is a traditional method of surveying that involves measuring linear distances and angles between points to determine the relative position of points on or near the earth's surface. The process involves the use of a chain or tape, ranging rods, and angular measurement instruments such as a theodolite or a plane table. The measurements are recorded and used to produce a plan or map of the surveyed area. Chain surveying is still used in some cases due to its simplicity, but is generally considered to be less accurate than modern surveying techniques that make use of electronic instruments.

Principle of Chain Surveying

The principles of chain surveying are based on the idea of triangulation. Triangulation involves the measurement of distances and angles between points in a two-dimensional plane, which can then be used to determine the relative position of those points. In chain surveying, a chain or tape is used to measure distances, and an angular measurement instrument, such as a theodolite, is used to measure angles. The measurements are taken from one point to another, creating a series of triangles that connect all the points in the surveyed area. The angles and distances are then used to calculate the position of each point relative to the others and to create a plan or map of the surveyed area.

Main survey station

The main survey station is a point of reference in chain surveying. It is typically established at the beginning of the survey and serves as a starting point for all subsequent measurements. The main survey station is usually a permanent and easily identifiable point, such as a building corner or a marked tree. From the main survey station, distances and angles are measured to other points within the surveyed area, and these measurements are used to determine the relative positions of those points. The main survey station acts as a common reference point, allowing all measurements to be tied together and providing a basis for determining the positions of all other points in the surveyed area.

Main survey line

The main survey line is a line established in chain surveying that serves as a reference for subsequent measurements. The main survey line is typically established from the main survey station and runs in a straight line towards the next point to be surveyed. The main survey line is used as a baseline for subsequent measurements of angles and distances, which are then used to determine the relative positions of points in the surveyed area. The main survey line is usually the longest and most accurately measured line in the survey, and it is used to establish a framework for the rest of the survey. The main survey line is critical for ensuring the accuracy of the survey and is typically carefully measured and recorded.

Base line

A base line is a reference line used in surveying. It is a line of known length and orientation that serves as a foundation for the measurement of angles and distances to other points in the surveyed area. The base line is typically established at the beginning of a survey and is used as a reference for subsequent measurements. In chain surveying, the main survey line is often used as the base line. The accuracy of the base line is critical for the accuracy of the entire survey, and it is typically carefully measured and recorded. The base line is used to establish a framework for the rest of the survey, allowing all measurements to be tied together and providing a basis for determining the positions of all other points in the surveyed area.

Check lines or proof lines

Check lines or proof lines are lines established in chain surveying to verify the accuracy of previously made measurements. They are additional lines, often shorter in length, that are run parallel to the main survey line and used to check the accuracy of the previously made measurements. The check lines are used to detect any systematic errors in the measurements and to ensure that the relative positions of points in the surveyed area have been accurately determined. If a check line measurement is significantly different from the corresponding measurement on the main survey line, it may indicate a mistake in the original measurement and allow it to be corrected before the survey is completed. Check lines play an important role in ensuring the accuracy of the survey and are typically carefully measured and recorded.

Subsidiary stations

Subsidiary stations are points established in chain surveying to aid in the measurement of angles and distances between other points in the surveyed area. They are typically intermediate points established between the main survey station and the points being surveyed. Subsidiary stations are used to break down the surveying process into smaller, more manageable parts and to improve the accuracy of the survey. By establishing subsidiary stations, angles and distances can be measured between the subsidiary station and other points, which can then be used to calculate the relative positions of those points. Subsidiary stations play an important role in ensuring the accuracy and efficiency of the survey, and they are typically carefully located and recorded.

Tie lines

Tie lines are lines established in chain surveying to connect two or more points in the surveyed area. They are used to connect points that cannot be directly measured from the main survey line or subsidiary stations. Tie lines are typically shorter in length than the main survey line or check lines and are used to fill in gaps in the survey data. By measuring the distance and angle between two points using a tie line, the relative position of those points can be determined. Tie lines play an important role in ensuring the completeness of the survey and are typically carefully measured and recorded. They are used to connect points that have been measured from different parts of the survey and to provide additional information that can be used to verify the accuracy of the survey.