Surveying and its applications
The art or technique to determine the position of points and angles and distance between them is known as Surveying. Surveying is necessary for making the map and for planning the project. Surveying is used to complete all civil engineering projects. Surveying means the accurate measurement of the earth’s surface. Surveying includes the determination of horizontal and vertical points that are used for mapping and the marking of the control point. Surveying is necessary for the planning and execution of the project. There are many instruments used for surveying such theodolite, total station, staff, and EDMI.
Surveying is an essential part of civil engineering. Depending upon the type of project, various kind of surveying is involved. Surveying is a technique to obtaining a position above or beneath the surface of the earth. There are two types of surveying
Plane surveying includes the small areas on the surface of the earth, assuming that surface is plane. The curvature of the land is neglected. Plane surveying includes:
- Chain surveying: In chain, surveying area is divided into triangles. The length of the sides is measured and recorded, and they are platted on the sheet with a suitable scale.
- Traverse Surveying: In traverse surveying plot of the plan includes a series of right triangles, and the length of lines and angles are drawn with detail.
- Plane table surveying: A sheet is fixed on a plane table, and all the observations are recorded side by side on the sheet, and then the map is drawn.
Geodetic surveying includes vast areas, and curvature is considered. The survey department of the country performs the geodetic survey. It is the type of surveying in which the curved shape of the earth is taken into account. The object of the geodetic study is to determine the precise position on the surface of the earth, of a system of widely distant points which form control stations in which surveys of less precision may be referred. The line joining two points is considered as a curved line, and angles are assumed as spherical angles. It is carried out if the area exceeds the 250-kilometer square. Geodetic surveying includes:
- Triangulation: In triangulation, triangles are formed on the plot to be surveyed. One line is considered baseline, and others are measured accordingly.
- Reciprocal Leveling: Reciprocal leveling is done near streams to avoid instrumental errors.
- Stadia surveying: In stadia surveying, the telescope instrument is used to measure distance. A surveyor takes theodolite, and another surveyor takes staff. Stadia measure vertical and horizontal distances.
Instruments used in Surveying
Surveyors measure the distance and angles, so they used many types of instruments such
- Chains and tapes: Surveying aims to measure the accurate distance. There is a variety of devices used to measure distances like chains, rules, and tapes. We have seen pocket tapes in our daily routine there are used to measure small gaps, and wheel tapes are used for the large scale measurement. Nyclad tapes are used harsh conditions and climate, and they are Nyclad good in resisting expansion. Fiber tapes are also used because of their low weight and portable for taking them to any place. There are many disadvantages of tapes, such as expansion and pull error. Laser measuring devices are also used to measure slopes and inclinations, vertical and horizontal calculations as well.
- Compasses and Clinometers: Compass is a useful instrument when we are in unfamiliar territory. Clinometers are used to measure the angle between two points, and compasses are used to measure the distance between two points. The compass survey uses the principle of traversing. This method does not require the need to create triangles. It uses a prismatic compass for measuring the magnetic bearing of line, and a chain measures the distance. A series of connecting lines is prepared using a compass and measuring distances using a chain. Interior details are located using offset from main survey lines.
- Theodolite: Theodolite is used to measure the horizontal and vertical angles. The accuracy of theodolite is one minute.
- Levels: Auto level is used to measure the difference in elevation between two points
- Prism and Reflectors: Prism and reflectors are used to secure control points. These devices are placed on the poles for the connection with electronic devices such as EDMI electronic distance measuring instrument, which also known as distance meter.
While dealing with the instruments, some errors occurs during handling of the instrument or during the measuring and these errors to be corrected for increasing the accuracy. Such type of errors is:
- Instrumental: This error arises due to the improper functioning of the instrument. Like short or long tape or measuring angle without adjustment.
- Personal error: This error appears due to improper handling of the device by the human, taking the wrong level reading.
- Natural: These errors occur due to temperature, weather, wind, or gravity. If these errors are not taken under observations, then results will belong.
Surveying helps in many phases of engineering, such as planning, execution, and mapping. The use of surveying starts from the initial phase of construction till the final phase of construction like the layout of the building and measuring vertical and horizontal points, measuring accurate distances, measuring depression and elevation. Surveying is used to make topographical maps that show the valleys, hills, and rivers. It is also used to make cadastral maps that show the boundaries of field and houses and to show engineering works such as buildings, roads, dams, and railways. The practice of surveying starts from the initial phase until the ending stage. Surveying is an essential part of civil engineering. For example, if an apartment is constructed, then first surveyors are needed to mark the point for the leveling and scoring control points. From a massive project to small projects surveying play its role. In highway construction, project surveying plays a vital role in measuring the leveling with accuracy because they are high budget projects, so smaller mistakes become dangerous.