Introduction

A control survey refers to a survey conducted to map out the positions of existing control points in the survey area. It is a crucial step toward the accurate measurement of distance and angles in the area. It is used to establish a control network of points, and surveyors must ensure the accuracy of these points before any further surveying process can be carried out.

In this article, we will discuss what a control survey is and its importance.

What is a Control Survey?

Control surveying is a method of surveying and mapping that uses a set of standard survey points as reference points for all subsequent surveys. These control points are established before the primary survey work is started, and are typically placed in locations that are easily identifiable and can be used as reference points for all subsequent surveys.

Control points are usually established using GPS or other precise surveying instruments and these points are then marked on the ground with metal pins or other markers, and a reference point is established. Once the control points are established, they are used as the basis for all subsequent mapping and surveying work. All points are then measured relative to the control points. This allows for precise and accurate surveying and plotting. 

This is why control surveying is essential and used for a variety of purposes, including engineering and construction projects, land mapping, and archaeological surveys. It is also used in many other fields, including geology, forestry, and hydrology because it is essential for any project that requires precise measurements and plotting.

Control Surveying is a very important part of any surveyor’s job because by establishing a set of control points, surveyors can guarantee that all data collected is accurate and consistent.

Types of Control Survey

There are two types of control surveys: horizontal control survey and vertical control survey.

1. Horizontal Control Survey: This type of control survey is used to measure the position of the points in the horizontal plane. The surveyor will measure and record the coordinates of the points in the x and y directions. This type of survey is often used for mapping and engineering surveys. Typically, horizontal control surveys are used to establish the horizontal position of points in a survey network and also used to measure distances and angles between points and to establish the relative positions of points in a plane. Horizontal control surveys are used to establish coordinate systems, such as State Plane Coordinates, and are essential for accurate map-making. 

2. Vertical Control Survey: This type of control survey is used to measure the elevation of the points in the survey area. The surveyor will measure and record the coordinates of the points in the z-direction. This type of survey is used for topographic surveys and civil engineering projects such as the elevation of a building or the height of a mountain. Vertical control surveys are essential for mapping activities, such as topographic mapping, and are used to establish the vertical datum of a coordinate system.

Both horizontal and vertical control surveys are essential for accurate mapping activities. The two types of surveys provide the framework for other surveys, such as topographic surveys, and are essential for the establishment of coordinate systems. Without the use of control surveys, it would be impossible to accurately map the features of the earth’s surface.

Processes of Control Survey  

The process of control survey is the process of identifying and mapping any changes in the area of interest, whether it is in a built or natural environment. It is essential for the accuracy of the mapping process, and it involves the use of various measurement techniques, such as distance measuring, direction establishment, locating a position, and surveying with a total station.

1. Doing Reconnaissance: The first step in the process of control survey is reconnaissance. This involves gathering information about the area of interest, including the features of the land, the current terrain, and any existing landmarks. This information is then used to develop a plan for the surveying process.

2. Distance Measuring: The second step in the process of the control survey is distance measuring. This involves measuring the distance between two points and determining the relative positions of those points. This can be done using a variety of tools, including a tape measure, a rangefinder, or a GPS unit.

3. Direction Establishment: The third step in the process of the control survey is direction establishment. This involves establishing the direction of the survey line, or the direction of the line of sight. This is done by measuring the angles between two points, or by using a compass to measure the direction of the line.

4. Locating a Position: The fourth step in the process of the control survey is locating a position. This involves finding the exact location of a point on the ground. This can be done using a GPS unit, or by using a total station to measure the angles between a point and two other points.

5. Surveying with a Total Station: The fifth step in the process of a control survey is surveying with a total station. This involves using a total station to measure the angle and distance between a point and two other points. This is done by measuring the angles between the points and entering the data into a computer. The computer then calculates the exact location of the point.

These are the five steps involved in the process of a control survey. It is important to understand and follow these steps in order to ensure that the survey is accurate and reliable.

Importance of Control Survey

The importance of a control survey cannot be underestimated. It is used to ensure that the project is built according to the plan and specifications, and is also used to verify the accuracy of the measurements taken during the construction process. 

Without a control survey, it would be impossible to know the exact locations of points on the earth’s surface, which would be necessary in order to accurately construct the project.

Control surveys are also used to establish the boundaries of properties and land parcels, as well as to create topographic maps. They are essential for making sure that a project is built according to the plans and specifications, and that the measurements taken during construction are accurate. 

Without a control survey, the construction process would be much more complicated and time-consuming.

Control surveys are also used to ensure that the project is built in a way that meets all regulations and standards, also the surveyor must ensure that all points in the control network are accurately measured and recorded so that no one is in danger of falling or being injured.

Without a control survey, it would be impossible to know whether the project was built in accordance with the necessary safety codes and regulations.

Conclusion

Control survey is an important step in the surveying process, as they are used to ensure that the project is built according to the plans and specifications and that the measurements taken during construction are accurate.

The accuracy of the measurements and the control network are essential for the accuracy of the survey data. This is why the surveyor must ensure that all points in the control network are accurately measured and recorded.