Principles of Surveying: Definitions, Classification, and Objectives

Hello friends! Today, we will be discussing the principles of surveying. Surveying is the art and science of measuring horizontal and vertical distances on or near the surface of the Earth. It plays a crucial role in determining the relative position of various points or stations on the Earth's surface, and is used in a wide range of applications such as mapping, boundary establishment, and site selection for engineering projects.

Definition of Surveying

Surveying can be defined as:

- Technical Definition: 

To determine the relative location of particular points near the surface of the Earth, and to measure the vertical distances between objects or angles between lines, or determine the location of points on or above the Earth's surface.

- Practical Definition: 

The art and science of determining the relative position of various points or stations on the surface of the Earth by measuring horizontal and vertical distances, angles, and taking detailed observations to prepare maps or plans.

The main function of surveying is to prepare accurate maps or plans.

Objectives of Surveying

The objectives of surveying can be broadly categorized into three main purposes:

1. Mapping: 

Surveying is used to find the relative position of points and prepare maps. These maps are essential for various purposes, including land development, infrastructure planning, and resource management.

2. Boundary Establishment: 

Surveying plays a crucial role in establishing the boundaries of land. Whether it's purchasing a plot or dividing a country into states, surveying helps in accurately measuring and defining these boundaries.

3. Site Selection for Engineering Projects:

Surveying is essential for selecting suitable sites for engineering projects, such as residential and commercial developments, railway lines, metro lines, bridges, etc. Topographical and contour maps, which are derived from surveying, provide valuable information for site selection.

Classification of Surveying

Surveying can be classified into two types: primary survey and secondary survey.

Primary Survey

1. Plane Survey: 

In plane survey, the surface of the Earth is considered as a flat plane. The lines joining any two points are treated as straight lines, ignoring the curvature of the Earth's surface.

2. Geodetic Survey: 

Geodetic survey takes into account the curvature of the Earth. The lines joining any two stations are considered as curved lines, considering the Earth's spherical shape.

Secondary Survey

Secondary survey can be classified based on instruments, methods, and objects.

- Based on Instruments: 

Chain survey, compass survey, plane table survey, theodolite survey, and photogrammetric survey.

- Based on Methods: 

Triangulation survey and traverse survey.

- **Based on Objects**: Geological survey, mine survey, agricultural survey, and military survey.

- **Based on Nature of Field**: Land survey, marine survey, and astronomical survey.

Principles of Surveying

To ensure accurate and reliable survey results, surveying follows two main principles:

1. Work from Whole to Part: In large area surveys, a system of control points is identified and located with high precision. Secondary control points are then located using lesser precision methods. The localized details of the area are measured and plotted with respect to these control points. This principle ensures that errors are minimized by working from the boundaries towards the center.

2. Locate a Point by at Least Two Measurements: When locating a single point, at least two measurements are required. These measurements can be linear or angular. By using two measurements, such as distances or angles, the point can be accurately plotted. This principle ensures the reliability and accuracy of the survey results.

In conclusion, surveying is a vital discipline that helps determine the relative position of points on the Earth's surface. By following the principles of surveying and using the appropriate classification methods, accurate maps, plans, and boundaries can be established, providing valuable information for various applications.