In a world driven by precise measurements and accurate land mapping, the field of surveying plays a pivotal role. Surveying involves the measurement and mapping of land, gathering crucial data for various purposes. This article aims to provide an in-depth understanding of the classification of surveying, exploring different techniques, tools, and applications.
What is Surveying?
Surveying is the science and art of measuring and mapping the physical features of the Earth’s surface. It involves determining distances, angles, elevations, and positions with high precision. The data collected through surveys is used for designing, planning, and constructing various projects.
Classification of Surveying:
There are various types of surveying that are conducted in Civil engineering works. Those different types of surveying are mainly classified into two types of classification of surveying.
- The primary classification of surveying
- The Secondary classification of surveying
A. Primary classification of surveying:
The primary classification of surveying is done based on the desired accuracy. In primary classification, surveying is classified into two types.
- Plane surveying
- Geodetic surveying
1.Plane surveying:
The surveying in which the effect of the curvature of the earth is not considered is called plane surveying. The ground surface is assumed to plane in this type of surveying.
We know that the earth is a spheroid. Hence the earth’s surface is obviously curved. But when we deal with a small area of its surface, we assume that the surface is a plane surface. So, when the area of surveying is less than 250 sq. km, then we generally ignore the curvature of the surface.
So in the case of such surveying (i.e., Plane surveying), we assume that
(i) A line joining any two points on the earth’s surface, is considered to be a straight line.
(ii) The triangle formed by joining any three points on the curved surface of the earth is considered a plane triangle. The angles are assumed as plane angles, not spherical angles.
(iii) A level line is assumed as a straight line and therefore the plumb line at any given point is assumed to be parallel to the plumb line at any other point.
(iv) The meridian passing through any two points is assumed to be parallel.
2. Geodetic surveying:
In geodetic surveying, the shape (curvature) of the earth is considered. Geodetic surveys extend over a large area (greater than 250 sq. km). In this type of survey, a higher degree of accuracy is applied in linear and angular measurements.
In the case of Geodetic surveying, we consider that
(i) A line jining any two points on the surface of the earth is considered as a curved line.
(ii) The triangle formed by joining any three points on the curved surface of the earth is considered as a spherical triangle.
B. Secondary classification of surveying:
1.Classification of Surveying based on Instruments:
(a) Chain surveying– Generally linear measurements are taken with a chain and tape. But In Chain surveying, no angular measurements are taken. The main instrument in chain surveying is a metallic chain. The principle of chain surveying is triangulation. Chain surveying is suitable for small areas with level grounds. It is a relatively simple and inexpensive method that is often used for small-scale surveys and for preliminary surveys for larger projects. Chain surveying is not suitable for areas with sloped ground or highly undulated areas. It is also known as “tape surveying.”
(b) Compass surveying– In compass surveying both the linear and angular measurements are taken. Horizontal angles are measured with a compass ( prismatic or surveyors compass) and linear measurements are taken with tape or a chain. Compass surveying is suitable for small areas with level ground. The compass surveying is not suitable for areas with high magnetic influence. It is often used in conjunction with chain surveying or tape surveying.
Compass surveying is mostly used in the early stages of a survey project, for reconnaissance and layout of the different survey lines. It is a relatively simple and inexpensive method, but it does have a few limitations, such as being affected by local magnetic attraction and thus so not providing accurate measurements over long distances.
It is also known as “directional surveying” or “bearing surveying.”
(c) Plane table surveying-It is a method of land surveying that uses a flat board, called a plane table, to prepare a map of an area by plotting the points directly on that board. Fieldwork and plotting are done simultaneously in this method. This method is the most rapid method of surveying. The principle of the plane table survey is parallelism. In this method, there is no possibility of overlooking any object or measurement as the plotting is done in the field. This method of surveying does not provide the most accurate results.
(d) Levelling– In Levelling the relative vertical height and vertical distance of different points are measured. The relative position of different points is calculated in leveling. The auto-level and graduated staff are the main instruments in leveling.
(e) Theodolite surveying– The theodolite survey is generally used in triangulation and traversing. Theodolite is called a universal instrument in surveying because of its various capabilities. The theodolite can be used for measuring-
- horizontal angles
- vertical angles
- deflection angles
- magnetic bearings
- the horizontal distance between two points
- the vertical height of an object
- ranging a line
- difference of elevation between various points.
(f) Tacheometric surveying- A tachometer is a transit theodolite fitted with a stadia diaphragm and anallatic lens. In this type of surveying the horizontal distance and vertical distances are obtained by taking only angular measurements. The chaining is completely eliminated in tacheometric surveying. This method is adopted for areas with highly undulated areas.
(g) Photographic surveying- In this type of surveying aerial photographs are taken by aerial methods, then they are plotted in the office.
(h) Electromagnetic distance management (EDM) surveying- Distance measured using the propagation, reflection, and reception of radio or light waves.
(i) Total-station surveying– Total station combines EDMs and electronic data collectors, reads, and records horizontal and vertical angles, along with slope distances.
(j) Satellite-based surveying-Remote sensing and global positioning system (GPS) are used to detect and take measurements.
2.Classification of surveying based on methods:
(a) Triangulation surveying: In the triangulation method of surveying method the entire surveying area is initially divided into a network of triangles. There are two types of triangles in surveying.
Well-conditioned triangle: All the angles are more than 30 degrees and less than 120 degrees.
Ill-conditioned triangle: If any of the angles is less than 30 degrees or greater than 120 degrees, the triangle is called an ill-conditioned triangle.
In triangulation surveying, the well-condition triangles are preferred because of their Sharpe apex points.
(b) Traverse surveying: In traversing, the linear measurements are taken with a chain. The angular measurements are measured with a magnetic compass. There are two types of traverse surveying that is performed.
The open traverse surveying is done for the surveying of boundary lines, and road alignments.
In closed traverse surveying, the surveying area is enclosed within a closed boundary with survey lines.
3. Classification of surveying based on the place of the survey:
(a) Land Surveying: The land survey is subdivided into the following types
(i) Topographical surveying- to determine the elevation and location of a country’s artificial and natural features.
(ii) Cadastral surveying or Public land survey-to determines the boundaries of fields, houses, and property lines.
(iii) City surveying- to determine the location of premises, streets, water sully and sanitary system, etc.
(b) Hydrographic surveying: The survey of water bodies such as lakes, streams, and coastal waters.
(c) Underground surveying: For the preparation of underground plans, fixing the direction and layout of tunnels and shafts, etc.
(d) Aerial surveying- It is the method of collecting geographical information using aerial photography such as UAVs, balloons, helicopters, and airplanes.
4.Classification of surveying based on the purpose of surveying:
(a)Engineering surveying– This surveying method is also known as construction surveying. Engineering surveying includes all the surveying work from starting to the completion of an engineering project.
(b)Defence surveying-Defence surveying is done in the military. This surveying method provides strategic information for the defense and attack plans. Aerial and topographical surveying methods are mainly used in defense surveying.
(c) Mine surveying– In the mine surveying method underground and surface surveying is done. Mine surveying is done for fixing the positions and directions of the underground structures.
(d) Archeological surveying: For excavating an area of historical importance archaeological surveying is done. An archaeological map enables easy unearthing of historical relics.
(e)Geographical surveying: For preparing geographical maps, geographical surveying is done. Geographical surveying provides sufficient data for the preparation of a geographical map.
(f)Geological surveying: To determine the location and storage of sub-surface minerals and rocks, geological surveying is done. Geological surveying is very important for projects like dams and bridges etc.
(g)Route surveying: Route surveying is done to collect information and establish a highway or railway alignment. Reconnaissance surveys, preliminary surveys, and control surveys are the sequences of route surveying.
Applications of Different Surveying Techniques
The diverse range of surveying techniques finds application in various fields. Here are some key applications:
- Land Development and Construction: Surveying ensures accurate site preparation, foundation layouts, and infrastructure development, contributing to successful construction projects.
- Mapping and Cartography: Surveying forms the foundation for accurate mapping, charting, and cartographic representations of landscapes, cities, and regions.
- Environmental Analysis and Conservation: Surveying aids in monitoring environmental changes, assessing land degradation, and planning conservation efforts for ecosystems.
- Infrastructure Planning and Design: Precise surveying measurements enable efficient planning and design of roads, bridges, railways, airports, and other critical infrastructure.
- Archaeological Research and Preservation: Surveying techniques assist in documenting archaeological sites, conducting excavations, and preserving cultural heritage for future generations.
- Geodetic Datums and Coordinate Systems: Geodetic surveying establishes global reference frameworks and coordinate systems for navigation, positioning, and geospatial data management.
The Role of Technology in Surveying
Advancements in technology have revolutionized the field of surveying. Here are some notable technological innovations:
- Advancements in Total Stations and GPS Receivers: Total stations combine electronic distance measurement and theodolite functions for accurate and efficient surveys. GPS receivers offer satellite-based positioning for precise coordinates.
- Laser Scanning and LiDAR Technology: Laser scanning enables the creation of highly detailed 3D models by capturing millions of data points. LiDAR (Light Detection and Ranging) technology aids in terrain mapping and vegetation analysis.
- Unmanned Aerial Vehicles (UAVs) in Surveying: UAVs equipped with cameras and LiDAR sensors provide aerial data collection, offering cost-effective and rapid surveys for large areas.
- Geographic Information System (GIS) Integration: GIS technology allows surveyors to analyze and manage survey data spatially, facilitating better decision-making and data visualization.
Challenges and Limitations in Surveying
Surveying is not without its challenges. Some common obstacles include:
- Adverse weather conditions affecting data collection
- Limited accessibility to remote or rugged areas
- Accuracy limitations due to equipment errors or environmental factors
- Cost and time constraints for large-scale surveys
- Complex legal regulations and property rights issues
- Data processing and management complexities
Navigating these challenges requires expertise, adaptability, and continuous technological advancements.
Frequently Asked Questions (FAQs)
- What is the purpose of surveying?
- Surveying serves to measure, map, and analyze the Earth’s surface for various purposes such as land development, construction, and environmental analysis.
- How does land surveying contribute to construction projects?
- Land surveying provides accurate measurements and boundary identification, enabling precise site planning, infrastructure design, and construction layout.
- What are the essential tools used in surveying?
- Essential surveying tools include total stations, GPS receivers, theodolites, levels, measuring chains or tapes, and various optical and electronic devices.
- How does GPS technology enhance surveying accuracy?
- GPS technology provides highly accurate positioning and coordinates, allowing surveyors to establish precise reference points and measurements.
- Is surveying necessary for property boundary identification?
- Yes, surveying is crucial for accurately identifying property boundaries and resolving disputes between landowners.
- What are the benefits of using LiDAR in surveying?
- LiDAR technology enables rapid and detailed terrain mapping, volumetric analysis, and vegetation identification, making it valuable for surveying and environmental studies.
- How can surveying help in environmental impact assessments?
- Surveying provides essential data for assessing environmental changes, monitoring land degradation, and identifying potential ecological impacts of development projects.
- Can surveying be used for archaeological site documentation?
- Yes, surveying techniques assist archaeologists in mapping and documenting ancient sites, artifacts, and cultural heritage for research and preservation purposes.
- What is the difference between geodetic and plane surveying?
- Geodetic surveying involves large-scale surveys over vast areas, focusing on establishing accurate geodetic reference frameworks and coordinate systems. Plane surveying is limited to smaller areas and does not account for the Earth’s curvature.
- How has surveying evolved over time?
- Surveying has evolved significantly with advancements in technology, from traditional chain and compass surveys to the integration of GPS, remote sensing, and 3D scanning technologies for faster and more accurate data collection.
Conclusion
Surveying is a multidisciplinary field that plays a vital role in various industries. Through the classification of surveying based on the nature of the object and surveying methods, professionals can select the most appropriate techniques and tools for accurate measurements and detailed land analysis. With advancements in technology and the constant evolution of surveying practices, this field continues to unlock new possibilities for precise mapping, construction, environmental analysis, and preservation. By understanding the classifications and applications of surveying, you have taken the first step towards exploring the vast world of surveying and its impact on our everyday lives.