What is Surveying?
Surveying is a process of determining the relative positions of objects on the earth’s surface by measuring horizontal distances between them and creating a map to a suitable scale. It involves taking measurements in the horizontal plane and is an art form that requires skill and precision. Surveying is used to create maps that show the natural features of a certain area such as towns, villages, roads, railways, etc., as well as engineering works such as bridges, canals and dams.
Why is Surveying Important?
Surveying is important for many reasons. It is used to prepare a map that shows the relative positions of objects on the surface of the earth and can be used to understand the topography of an area, along with natural resources that may be available. Surveying is also used to create a cadastral map that shows property boundaries, which is essential for any major engineering project. Additionally, surveys are used to determine the location of a site and its surroundings before the commencement of such a project.
How is Surveying Carried Out?
Surveying is carried out by taking direct or indirect measurements of distance, direction and elevation. This data is then used to calculate the relative positions of the objects on the surface of the earth and to create a map. The map can then be used to understand the topography of an area and make decisions about engineering projects.
Principles of Surveying
- Fundamental Principle of Plane Surveying
The fundamental principle upon which the various methods of plane surveying are based is the application of geometry and trigonometry to the measurement of distances, angles, and areas on or near the surface of the Earth. This involves the use of surveying instruments such as theodolites, levels, transits, and EDM instruments. These instruments are used to measure angles and distances between points on the surface of the Earth, which are then used to calculate areas and coordinates. - Applications of Plane Surveying
Plane surveying is used for a variety of purposes, including mapping, land development, construction, and engineering projects. It is also used for the measurement of features such as rivers, roads, and other features on the surface of the Earth. Plane surveying is also used to measure the contours of land and to create contour maps, which are used for engineering and construction projects.
Location of a point by measurement from two points of reference
Principle of Triangulation
The Principle of Triangulation is a surveying technique used to determine the relative position of a point to be surveyed in relation to two points of reference, whose positions have already been established. The process involves the use of geometry, specifically triangles, to determine the relative position of the point being surveyed. This is done by measuring the length of each side of the triangle and using the data to calculate the angles at each vertex. Once all the measurements have been obtained, the coordinates of the point being surveyed can be determined.
Method of Locating Point R with Respect to Reference Points P & Q
In order to find the relative position of point R with respect to reference points P and Q, any of the direct methods shown in the figures can be utilized. One method is usually sufficient to determine the exact location of the point R, however, it is necessary to use at least two different methods to make sure the position of point R is accurately fixed. Using one method to measure the distance between P, Q and R can provide an estimate of the point’s location, while a second method can be used to confirm the accuracy of the measurements.
Working from whole to part
What is the Principle of Whole to Part?
The Principle of Whole to Part is a method of surveying which advocates for the establishment of a system of control points for an area which need to be surveyed, with high precision. This is followed by the surveying of minor details with less precision.
Why is this Principle Necessary?
This principle is necessary to prevent the accumulation of errors, and to control the minor errors from expanding to greater magnitudes. If the reverse process is followed, the surveying work would become uncontrolled at the end.
Method of Surveying in Civil Engineering
Primary types of Surveying are:
- Plane surveying
- Geodetic surveying
1. Plane surveying
What is Plane Surveying?
Plane surveying is a method of surveying that disregards the curvature of the Earth and considers the earth’s surface to be flat. This type of surveying is used when the surveyed area is less than 250 km2. All triangles formed by survey lines are considered as plane triangles, with level lines being considered as straight and plumb lines being considered parallel. Plane surveying is conducted by both state and private agencies.
Why is Plane Surveying Used?
Plane surveying is used when the area of survey is relatively small and the curvature of the Earth can be safely ignored. This type of surveying is often used in the construction of buildings, roads, and other infrastructure projects. Plane surveying is also used by state and private agencies to conduct surveys of small areas.
2. Geodetic surveying
Geodetic Survey: A Comprehensive Overview
Geodetic survey is a type of surveying conducted by the survey department of a country that takes into account the curved shape of the earth. The main purpose of geodetic survey is to accurately determine the position of a system of widely-distant points that form control stations, onto which less precise surveys can be referred. This type of survey is implemented if the area of the study exceeds 250 km2 and the lines joining two points are assumed to be curved, with angles measured as spherical angles.
Benefits of Geodetic Survey
Geodetic surveys provide numerous advantages for planning and mapping projects. By accurately positioning control stations, geodetic surveys allow for the creation of high-precision maps and plans. Additionally, this type of survey allows for the determination of the exact distance between two points, which is important for a range of applications such as engineering and construction projects. Geodetic surveys also allow for the calculation of the volume of land masses, which is useful for land management. Finally, geodetic surveys can be used to accurately measure elevation and other topographical features, which is useful for environmental monitoring.
Secondary classification of Surveying
Classifying Surveys Based on Nature of Field
Surveys can be classified according to the nature of the field they are conducted in. This includes surveys of consumer behaviour, market research, customer satisfaction, health and medical surveys, political opinion polls, employee surveys, and more. The type of survey chosen will depend on the research objectives and the target audience.
Classifying Surveys Based on Object of Survey
Surveys can also be classified based on the object of the survey. These include surveys of individuals, communities, organizations, and businesses. The survey’s purpose and target audience will determine the object of the survey. For example, a survey of individuals may be used to gauge public opinion, while a survey of businesses may be used to assess customer satisfaction.
Classifying Surveys Based on Instruments Used
Surveys can also be classified based on the instruments used to collect data. These include surveys conducted through telephone interviews, mail surveys, online surveys, and face-to-face interviews. The instrument chosen will depend on the needs of the research and the target audience. For example, an online survey may be best suited for a large population while a face-to-face interview may be best suited for a smaller target audience.
1) Surveying based on Nature of Survey
a) Topographical Surveys
What are Topographical Surveys?
Topographical surveys are surveys that are conducted to identify and map the natural and artificial features of a given region. These features may include rivers, streams, hills, roads, and canals. The maps that are created from these surveys are known as topo-sheets.
Purpose of Topographical Surveys
The main purpose of topographical surveys is to create maps that accurately represent the natural and artificial features of a region. These maps provide valuable information to engineers, surveyors, and other professionals who need to accurately identify and measure features for a variety of purposes.
Benefits of Topographical Surveys
Topographical surveys can be used for a variety of purposes, such as:
- Planning development projects
- Assessing the impact of developments on the environment
- Assessing land use potential
- Assisting in disaster management
- Assisting in the design of infrastructure
- Assisting in the construction of roads, dams, and other structures
Conclusion
Topographical surveys are essential for accurately mapping and measuring the natural and artificial features of a region. These surveys provide valuable information to a variety of professionals, and can be used for a wide range of purposes.
b) Hydrographic Survey
What is Hydro-Graphic Survey?
Hydro-graphic survey is a process of surveying and mapping of water bodies such as rivers, streams, lakes, and oceans. It is a specialized form of surveying which involves measuring and mapping the physical characteristics of a body of water. The data gathered can be used to understand the topography, bathymetry (depth), and hydrology (flow) of the water body.
What is the Purpose of Hydro-Graphic Survey?
The primary purpose of hydro-graphic survey is to determine the Mean Sea Level (MSL) of a water body, as well as other important characteristics such as the water spread area, the depth of the water body, the velocity of the flow in streams, and the cross-sectional area of the flow. This data can be used to analyze and plan for potential uses of the water body, such as navigation, fishing, and recreation. It can also be used to assess the potential for flooding or other natural disasters.
What Are the Benefits of Hydro-Graphic Survey?
Hydro-graphic survey provides a comprehensive view of a water body, allowing for more accurate and informed decisions to be made about its use and management. It also allows for better understanding of the physical characteristics of the body of water and its environment, which can help to protect it from potential damage or destruction. Hydro-graphic survey data can also be used to identify areas of potential risk, allowing for preventative measures to be taken in order to protect the water body from potential hazards.
c) Astronomical Survey
Astronomical Survey
An astronomical survey is an observational study of celestial objects in order to measure their positions and calculate their absolute locations on the surface of the Earth. By observing stars, galaxies, nebulae, and other celestial objects, astronomers can determine the exact positions and distances of these objects with respect to the Earth. This type of survey is used to map the positions of stars, planets, and other astronomical bodies, as well as to measure the positions of objects in the night sky.
d) Engineering Survey
What is an engineering survey?
An engineering survey is a type of survey undertaken to collect data for the purpose of engineering works such as roads, bridges, and reservoirs. It provides detailed information about the land, terrain, and other features such as water, vegetation, and buildings that are needed for engineering projects. It is also used to determine the exact location of features and to provide accurate measurements for the construction of the project.
Why is an engineering survey important?
An engineering survey is important because it allows the engineer to collect accurate data that can be used to design, plan, and construct the project. This information is essential to ensure the project is designed according to the engineer’s specifications and to ensure that it meets all safety requirements. It also helps to minimize costs and to ensure that the project is completed on time and within budget.
When is an engineering survey necessary?
An engineering survey is necessary whenever sufficient data needs to be collected for the purpose of planning and designing engineering works. The data gathered from an engineering survey can be used to accurately map out the area for the project, to determine the best construction methods and materials, to identify potential risks and hazards, and to assess the environmental impact of the project.
e) Archeological Survey
What Is An Archaeological Survey?
An archaeological survey is a type of survey used to gather information about sites that are significant from an archaeological perspective, such as those with relics of antiquity. The purpose of an archaeological survey is to assess the archaeological potential of a given site for further investigation.
What Information Can Be Gathered From An Archaeological Survey?
An archaeological survey can be used to determine the location, size, condition, and type of archaeological features present at a given site. This information is necessary for archaeologists to plan further surveys, excavations, and other activities related to understanding the site’s history and contributions to the archaeological record.
How Is An Archaeological Survey Carried Out?
An archaeological survey is typically conducted by a team of professional archaeologists and other specialists. This team will use a variety of methods to survey a site, including aerial photography, surface surveys, geophysical surveys, and remote sensing. These methods are used to identify, document, and interpret any archaeological features present at the site.
f) Photographic Survey
Photographic Surveying
Photographic surveying is a method of collecting information using a camera. In this type of survey, photographs are taken from pre-selected points to obtain data required for mapping, engineering, and other purposes. The photographs are then used to create detailed maps, plans, and 3D models of the area being surveyed. This method is often used for large-scale projects where many points need to be recorded quickly and accurately.
g) Aerial Survey
Aerial Surveying
Aerial surveying is a method of collecting data about large tracts of land by taking photographs from an airplane. This method provides an efficient way of gathering data over an expansive area and allows for the creation of maps and other visual representations of the land. Aerial surveying is used for a variety of purposes, such as urban planning, agricultural monitoring, and land use analysis.
h) Reconnaissance Survey
Definition of a Physical Survey
A physical survey is a method of collecting data by making physical observations and taking measurements using simple survey instruments. This type of survey is typically used in field research, such as in geology, engineering, cartography, and archaeology. It can also be used to assess the condition of a building or structure and to determine its features.
Benefits of a Physical Survey
Physical surveys offer a number of advantages compared to other data collection methods. For example, they are more accurate than surveys conducted over the phone or online, as physical measurements are taken and the data is collected in person. They also allow for direct observation of the area being studied, which can provide valuable insight. Additionally, physical surveys can be conducted quickly and cost-effectively.
Examples of a Physical Survey
A physical survey can be used to measure the dimensions of a site, such as its size, shape, and elevation. It can also be used to map out the terrain, as well as any features such as buildings, roads, and vegetation. Other uses include assessing the condition of a building or structure, as well as determining its features, such as the type of building materials or the presence of hazardous materials.
2) Surveying based on Type of Instruments
a) Chain Surveying
Overview of Chain Surveying
Chain surveying is the oldest and most basic form of surveying. It is used to survey small areas with little undulation on level ground. This method involves the principle of triangulation and the division of the area into a number of small triangles. The angles of these triangles must be between 30° and 120°, with equilateral triangles being the ideal shape. Measurement of angles is not necessary, as tie and check lines are used to ensure accuracy.
What is Involved in Chain Surveying?
Chain surveying is based on the principle of triangulation, which involves the division of the area into a number of small triangles. The angles of the triangles must be between 30° and 120°, with equilateral triangles being the ideal shape. No angular measurements are taken, as tie and check lines are used to control the accuracy of the work.
Benefits of Chain Surveying
Chain surveying is suitable for surveying small areas with little undulation on level ground. It is also a relatively simple and cost-effective method of surveying, as no angular measurements are taken. The tie and check lines used to control accuracy are also relatively easy to set up.
Limitations of Chain Surveying
Chain surveying is limited to surveying small areas with little undulation on level ground. It is not suitable for surveying large or hilly areas, as the accuracy can be compromised by the terrain. Furthermore, the accuracy of the results is dependent on the accuracy of the tie and check lines, which can be difficult to set up in certain conditions.
b) Compass Surveying
What is Compass Survey?
Compass survey is a surveying method that uses a prismatic compass for measuring the magnetic bearing of lines and a chain for measuring distances. It does not require the need to create triangles, making it suitable for large area surveying with many details.
How Does Compass Survey Work?
Compass survey uses traversing to connect lines, with interior details located using offset from main survey lines. The prismatic compass is used to measure the magnetic bearing of lines, while the chain is used to measure distances between lines.
What is Compass Survey Used For?
Compass survey is suitable for surveying large areas with many details, such as a river course. It can be used to create a series of connecting lines that can then be used to locate interior details using offset from the main survey lines.
c) Plane Table Surveying
What is the Principle of Plane Table Survey?
The principle of plane table survey is based on parallelism. This technique is used for plotting points on a flat surface, such as paper, with their relative positions to one another. This technique requires drawing rays from the station to the object on the ground. The table is then placed at each successive station in the same parallel position as the last station.
Advantages of Plane Table Survey
Plane table survey can be used to fill in interior details accurately. This method of surveying is also recommended when great accuracy is not required.
Limitations of Plane Table Survey
The accuracy of plane table survey is limited by the accuracy of the instruments used. This method of surveying is not suitable for large-scale projects, as it may take a considerable amount of time to collect the necessary data. Additionally, the data collected by this method is not as accurate as other surveying techniques.
d) Theodolite Surveying
What is a Theodolite?
A theodolite is a precision instrument used to measure horizontal and vertical angles. It is commonly used in surveying and civil engineering applications, and can deliver accurate readings up to 10″ or 20″ angles.
What Can a Theodolite Measure?
Theodolites can be used to measure horizontal angles, vertical angles, deflection angles, magnetic bearings, horizontal distances between two points, vertical heights between two points, and differences in elevation.
Replacement of Theodolites
In recent times, theodolites have been replaced by Total Stations, which can perform the same tasks as theodolites with greater accuracy and ease of use.
e) Tacheometric Surveying
What is Tacheometry?
Tacheometry is a branch of surveying in which horizontal and vertical distances are determined by taking angular observations with an instrument known as a tacheometer. A tacheometer is a transit theodolite fitted with a stadia diaphragm and an anallatic lens, allowing surveyors to do their work without the need for chaining.
The Principle Behind Tacheometry
The principle of Tacheometry is based on the property of an isosceles triangle, where the ratio of the distance of the base from the apex and the length of the base is always constant.
Common Types of Stadia Diaphragm
There are several different forms of stadia diaphragm commonly used in tacheometry. These include the basic stadia diaphragm, the right-angle stadia diaphragm, and the dual-axis stadia diaphragm.
f) Photographic Surveying
Photographic Surveying
Photographic surveying is a technique used to generate topographic details quickly and accurately. It involves taking photographs from different angles to capture information about a surveyed area. There are two main types of photographic surveying: Aerial Photography and Terrestrial Photography.
Aerial Photography
Aerial photography is the practice of taking photographs from a higher altitude, typically from the air. This method is commonly used to create large-scale maps and survey large areas. Aerial photography can also be used to study the environment, assess urban development, and create 3D models of landscapes and structures.
Terrestrial Photography
Terrestrial photography is the practice of taking photographs from the ground, typically from a tripod or other stable platform. This method is used to capture detailed images of a particular area and can be used to study features such as vegetation, geology, and water flow. Terrestrial photography can also be used to document archaeological sites, create high-resolution images for mapping purposes, and assess changes in land cover over time.
i). Terrestrial or ground photogrammetry
What is Terrestrial Photogrammetry?
Terrestrial Photogrammetry is a technique that uses photographs taken from the ground to measure and map the Earth’s surface. By taking images from different points on the Earth’s surface, it is possible to accurately measure and map objects in three dimensions. This technique is used for a variety of applications, such as mapping, surveying, and engineering.
How is Terrestrial Photogrammetry Used?
Terrestrial Photogrammetry is used to measure and map objects on the Earth’s surface. This technique is used in a variety of applications, such as mapping, surveying, and engineering. By taking photographs from different points on the Earth’s surface, it is possible to accurately measure and map objects in three dimensions. The resulting maps can be used for a variety of purposes, from engineering and construction to urban planning and disaster relief.
ii). Aerial photogrammetry
What is Photogrammetry?
Photogrammetry is the science of producing maps from aerial photographs taken from an airplane or helicopter. It encompasses two major areas of specialization: metrical photogrammetry and interpretive photogrammetry.
Metrical Photogrammetry
Metrical photogrammetry is of particular interest to surveyors as it is used to calculate distances, elevations, areas, volumes, etc. to compile topographic maps made from measurements on photographs.
Interpretive Photogrammetry
Interpretive photogrammetry involves analyzing objects from their photographic image and determining their significance. Factors such as shape, size, pattern, and shadows are considered when identifying objects.