Surveying is the art of determining the relative positions of points that are on, above, or beneath the earth’s surface using linear or angular measurements.
In this article, let’s discuss the various classification of surveying.
There are different classifications of surveying based on,
- The accuracy of surveying
- The nature of the field of surveying
- The surface object of the survey
- The method employed in the survey
- The instrument used
Let’s discuss each of them in detail.
1) The accuracy of surveying
Based on the accuracy of the surveying, the surveying can be classified into
- Plane surveying and
- Geodetic surveying
A) Plane Surveying
It is the classification of a survey in which the area to be surveyed on the surface of the earth is considered to be plane i.e the curvature of the earth is not taken into account
As the plane survey extends only for a small area, the lines that are connecting the two points on the surface of the earth are considered straight lines and the horizontal angle between the lines are treated as plane angles.
The survey which covers an area under or equal to 200 sq. km should be treated as plane surveying.
B) Geodetic surveying
It is the classification of a survey in which the curvature of the earth is taken into account because this type of survey is extended over a long area.
The lines connecting two points on the surface of the earth are treated as curved lines i.e arcs and the angle between these intersecting curved lines are treated as spherical angles.
The survey which is covering over an area of 200 sq. km should be treated as Geodetic surveying.
2) The nature of the field of surveying
Classification of surveying based on the nature of the field of surveying,
- Land Surveying
- Marine or Hydrographical Surveying
- Astronomical Surveying
Let’s discuss each of them in detail.
A) Land Surveying
This surveying consists of determining the length, shape, and size of the area of the land. It is also used to establish and locate the position of points in the land.
A land survey can be subdivided into the following surveys.
a) Topographical survey – It is used to determine the natural and artificial features of a country such as hills, valleys, forests, buildings, railways, canals, etc.
b) Cadastral survey – These surveys are carried out to fix the boundary line of the property and are used in the preparation of revenue maps of the state.
c) City survey – The survey which is carried out for the construction projects like roads, water supply systems, and sewer systems to develop the infrastructure for a particular city.
d) Engineering survey – This survey is used for collecting data that are required for the design of engineering works such as roads, railways, sewage, etc.
The engineering survey is further divided into three types namely,
- Reconnaissance survey – To determine the possibility and the rough cost of the project.
- Preliminary survey – For collecting more engineering data and choosing the best location to carry out the work.
- Location survey – Used to setting out the work on the field.
B) Marine or Hydrographical Surveying
It deals with the surveying of large water bodies for various purposes such as navigation, construction of ports and harbors, prediction of tides, and determination of average sea level, etc.
C) Astronomical Surveying
The survey which is carried out for locating the absolute location of the place on the earth’s surface by making an observation of the heavenly bodies i.e. sun and star is called an astronomical survey.
3) The surface object of the survey
Classification of surveying based on the object surface of the survey,
A) Archaeological survey – For determining and unearthing the ancient relics.
B) Geological survey – For determining and exploring the different stratus of the earth’s crust.
C) Mine survey – For exploring the mineral wealth of the nation such as gold, copper, coal, etc.
D) Military survey – For determining and establishing the strategic points for both offensive and defensive positions.
4) The method employed in the survey
Based on the method carried out, the survey is generally classified into
- Triangulation survey
- Traverse survey
A. Triangulation survey
The triangulation survey consists of the arrangement of the framework of triangles since a triangle is the only plane figure that can be plotted from the lengths of its sides alone.
The best shape of the triangle to be followed is an equilateral because an equilateral triangle can be plotted more accurately than an obtuse-angled triangle.
B. Traverse survey
A traverse survey is one of the classifications of surveying in which the framework consists of a series of connected lines.
The length and the directions of the line are measured with the help of a chain and an angular instrument respectively.
In traverse surveying, the directions of the survey line are fixed by an angular measurement device and not by forming a network of triangles.
5) The instrument used
Classification of surveying based on the instrument used,
1. Chain survey – This survey is used to measure distances with ease and is used for small areas with simple geometry. (Read more)
2. Compass survey – This survey uses a compass to determine the bearings or angles to establish the direction and location of a point. (Read more)
3. Plane table survey – In this method, a drawing board called a plane table is used to plot the position of points directly in the field with the help of other surveys like chain surveying. (Read more)
4. Theodolite survey – This survey uses a precise instrument called theodolite to measure the horizontal and vertical angles to determine the position of a point.
5. Tacheometric survey – This survey uses an instrument called a tacheometer, through which we can be able to measure both distance and angles of both accessible and inaccessible points.
6. Photographic survey – This surveying technique uses aerial photographs to create accurate models and maps of terrain and is often used for planning and monitoring.
7. Aerial survey etc.
Hope you understand everything you need to know about the Classification of surveying. If you find this article helpful (or) If you have any queries, let us know in the comment section.
Read more: 10 Important Types of levelling in surveying, 5 Types of levels used in levelling.
