A control survey establishes reference locations on land or a construction site. These control points precisely locate and map other land or site characteristics, including buildings, roads, and utilities.
Control surveys or survey controls provide reference points as a foundation for diverse building processes. A survey station is a location from which the observations are made.
All other types of surveys, including topographic, right-of-way, aerial mapping, construction layout, boundary surveys, and utility mapping, can be worked on after the control points are established to build control networks.
This blog will discuss what a control survey is, its types, and its importance.
What is a control survey?
Control surveys offer the horizontal and vertical positions of the points used to adjust supplementary surveys. Control surveys set the accuracy benchmark for subsequent and subsidiary surveys to meet.
Each project comprises a series of vertical and horizontal field surveys, including route surveys, photogrammetry, and topographic mapping. These follow-up surveys rely on relative accuracy and positional control.
Control surveys are used in project planning and construction to ensure accuracy and efficiency. Skilled surveyors perform control surveys utilizing total stations, GPS receivers, and level tools.
Control surveys are classed by accuracy and control point count. The most accurate control surveys are first-order, followed by second-order and third-order. Aerial and geodetic control surveys are also available.
Types of control survey
Control surveys can create reference points on land or a construction site. Essential types of control surveys include:
- First-order control survey: This is the most accurate kind of control survey, and it’s frequently used for big projects or projects that need a lot of accuracies. It connects a network of control points to provide a precise reference system for the project.
- Second-order control survey: Although less precise than a first-order survey, this control survey is appropriate for many medium-sized projects. It is frequently used for projects that ask for less accuracy and employ a lesser number of control points.
- Third-order control survey: These are the least accurate and often employed for small-scale or less accurate projects. It is appropriate for projects where an approximate location estimate is acceptable because they only use a small number of control points.
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Other types of this kind of surveys include geodetic control surveys, which use precise measurements of the earth’s curvature to set up control points, and aerial control surveys, which use aerial photographs or satellite imagery to set up control points.
Importance of control survey
A control survey is important for a lot of reasons. In the field of surveying and mapping, it is used to set up a precise reference frame for the location of points on the Earth’s surface. Most of the time, this is done using horizontal and vertical control points. These are set up using precise surveying methods like trigonometry and differential leveling.
Control surveys are also important for ensuring that other types of surveying and mapping work, such as topographic surveys, boundary surveys, and construction surveys, are accurate and precise.
With accurate control surveys, it would be easier to correctly find and measure points on the ground, which could lead to mistakes and inaccuracies in the final survey product.
Control surveys keep the integrity of geospatial data over time. By re-establishing control points regularly, it is possible to ensure that the reference frame used to find facts on the ground stays accurate and up-to-date, even if the landscape changes due to natural or human-caused processes.
Overall, these surveys are an important part of surveying and mapping. They help ensure that geospatial data and the products and services used are accurate and reliable.
Processes of control survey
Following is an itemized list of the steps that went into conducting the survey:
- Doing Reconnaissance:
Reconnaissance is the process of looking at a project area to see how well the fieldwork part of a project will work overall. Here are just a few of the many goals that the preliminary survey will set:
- To figure out how easy it is to get to the project area and whether or not there are other ways to get there.
- To evaluate the current state of project control and the possibility of other project points
- To figure out if field methods and other methods can work.
- To figure out what the limits of the environment are
- Laying the Stations:
There are various objectives to be decided upon when laying the station markers, some of them are as follows:
- To evaluate the most suitable survey markers to utilize
- To assess the intervisibility of desired project points
To determine whether the sky is visible at the project locations in case astronomical observations or GNSS are going to be used for positioning.
- Distance Measuring:
There are many methods for measuring lengths and distances, including taping, electromagnetic distance measuring (EDM), and, more recently, satellite technology methods.
- Direction Establishment:
In surveying, bearing and angle measurements are crucial. Establishing direction has been used for many survey operations, from utilizing Greco-Roman instruments to astro-geodetic positioning techniques.
- Locating a position:
Locating a location on a map or geographically.
A control survey’s conclusion would depend on the survey’s precise goals and objectives and the techniques utilized for data collection and analysis.
A control survey is carried out to determine the exact horizontal and vertical placements of points on the earth’s surface. A control survey aims to create a reference system to precisely pinpoint other places on the planet’s surface.
It is important to remember that a control survey’s outcome should be based on a comprehensive examination of the information gathered and the procedures followed to gather it and should be backed up by facts.
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