Chain Surveying: A Simple Method of Surveying
Chain surveying is a straightforward method of surveying in which measurements are taken in the field and further works such as plotting calculations are done in the office. Linear measurements are taken in chain surveying, while angular measurements are not taken into account. This type of surveying may provide accurate results as long as the work is performed carefully. It is suitable for small areas with few details and requires tools and equipment such as a chain, tape, ranging rod, arrows, and sometimes a cross staff.
Specifying Survey Stations for Accurate Results
In order to get accurate results from chain surveying, survey stations (main stations, tie or subsidiary stations) need to be specified carefully. If the survey stations are not specified accurately, the outcomes of the surveying process may be inaccurate.
Applicability of Chain Survey
Condition 1: Small Area
Chain surveying is an effective technique to measure distances in small areas, as it requires a fairly limited area to be mapped out.
Condition 2: Moderate Level Ground
Chain surveying should be used when the ground is moderately levelled, as it will provide accurate measurements.
Condition 3: Open Area
Chain surveying requires an open area, as it requires space to measure distances between two points.
Condition 4: Few Details
The area should have few and simple details, as this will make it easier to accurately measure distances.
Chain Survey Tools
- Chain
- Tape
- Ranging-Rod
- Arrows
- Cross staff
Chain Survey Stations
Types of Survey Stations
There are two main types of survey stations used in chain surveying: reference stations and turning points. Reference stations are points of importance at the beginning and end of a chain line, and are typically marked by monuments or other objects for easy identification. Turning points are intermediate stations that are typically set up at regular intervals to mark the length of the chain line. They are used to ensure that the length and direction of the line are measured and recorded accurately.
1. Main stations
Main Stations as End of Lines
Main stations are the end of lines that define the boundary of the surveying and mapping process. They are the points of reference for determining the extent of the survey or map. By using these stations, surveyors and cartographers can accurately measure the area being surveyed or mapped, and ensure that all the necessary data is collected. Main stations also provide a convenient way of connecting different parts of a survey or map together, allowing for easier navigation and data collection.
2. Tie (Subsidiary) Stations
What is a Tie Station?
A tie station is a point on a chain line or main survey line where it is necessary to accurately identify interior details such as buildings or fences. This point is used in order to ensure that the measurements and details taken from the survey are correctly plotted on the map. Tie stations are essential for providing precise and reliable data for surveying and mapping.
Factors Affecting Survey Station Selection
Visibility of Stations:
Ensuring stations can be seen from two or more locations is essential for successful surveying.
Level Ground:
For main survey lines, running them on level ground will decrease the risk of errors and inaccuracies.
Defined Triangles:
All triangles must be measured and checked properly to ensure accuracy, with no angle measuring less than 30º.
Check Lines:
To ensure accuracy, each triangle should have at least one check line.
Minimizing Survey Lines:
Surveyors should strive to minimize the number of survey lines used.
Avoiding Obstacles:
Surveyors should strive to avoid any obstacles that could interfere with ranging and chaining.
Boundary Lines:
When measuring larger triangles, survey lines should pass as close to boundary lines as possible.
Minimizing Trespassing:
To avoid any potential legal issues, surveyors should minimize trespassing and frequent road crossings.
Line Types in Chain Survey
1. Base Lines
What Is a Base Line?
A base line is a main and longest line used to determine measurements for a particular project. It passes through the center of a field and is used to provide details of the work being done.
Why Is a Base Line Important?
A base line is an important tool for accurately measuring distances in a project. It provides an accurate reference point for taking measurements and helps ensure accuracy in the project.
How Is a Base Line Used?
A base line is used to take measurements from in order to determine specific details of a project. It is typically used in surveying, mapping and construction projects.
2. Chain Line (Main Survey) Lines
What Are Chain Line or Main Survey Lines?
Chain line or main survey lines are the lines that connect main stations in a survey. These lines are critical components of accurate survey mapping, as they provide an essential reference point for calculation of distances and angles between the main survey points. By connecting the main points, a surveyor can form a comprehensive picture of the land surveyed, enabling a more accurate representation of features and measurements.
3. Tie (Subsidiary) Lines
What is a Tie Line?
A tie line is a line that connects two fixed points on a chain line. It is used in surveying to check the accuracy of interior details such as buildings and pathways.
Benefits of Using a Tie Line
A tie line is an effective tool for surveying accuracy. By connecting two fixed points on a chain line, it allows surveyors to accurately measure the locations of interior details such as buildings and pathways. This helps ensure the accuracy of their measurements.
4. Check (Proof) Lines
What is a Check Line?
A check line is a line that joins the apex of a triangle with two fixed points on its sides. It is used to assess the accuracy of the framework.
How is a Check Line Used?
A check line is used to examine the precision of the framework by comparing the length of the measured line on the ground to its length on the plan.
Offsets in Chain Survey
Offsets: A Definition
Offsets are lateral measurements taken from a baseline in order to accurately fix the location of various objects. They can either be perpendicular or oblique, depending on the required orientation. This article will provide a brief overview of the types and uses of offsets.
Types of Offsets
There are two primary types of offsets: perpendicular and oblique. Perpendicular offsets involve measurements taken at a right angle from the baseline. Oblique offsets involve measurements taken at any angle other than a right angle.
Uses of Offsets
Offsets are used to accurately locate objects in relation to a baseline. They are commonly used in surveying, mapping, and other fields where exact measurements are required. Additionally, they are often used in engineering and construction projects to ensure that objects are placed in the correct location.
Chain Survey Procedures
- Preparing the Area for Survey:
In order to begin the survey, it is important to inspect the area to be surveyed and prepare a key plan. This stage is referred to as the reconnaissance phase. During this process, stations are marked using suitable means such as placing ranging poles, driving pegs and digging and fixing a stone. The main line is also specified and marked in the center of the field. - Setting Up the Ranging Road:
Once the area is prepared for survey, the ranging road is set up on the stations. It is important to make sure that the ranging road is marked accurately to ensure that the survey is conducted accurately. - Starting the Chaining:
Once the ranging road is set up, the chaining can begin. During this process, ranging is done wherever necessary to measure the changes and offsets. All measurements are recorded. - Finalizing the Survey:
After all the measurements are taken and recorded, the survey is finalized. This involves reviewing the data collected and making any necessary adjustments to ensure accuracy. The survey can then be used to create the desired end product.
