To Carry Out the Surveying to Find Out the Contour Map of Given Site (smit Compound) & Do Profile Levelling

AIM

To carry out the surveying to find out the contour map of given site (SMIT compound) & do profile levelling.

INSTRUMENTS USED

Total station, measuring tape, prism, tripod stand, pegs, cross staff, and ranging rods.

THEORY

Surveying is the technique and the science of accurately determining the terrestrial or three dimensional positions of the points and the distance and the angles between them, which is commonly practiced by the surveyor and the various members of civil engineering profession generally.

These points are usually on the surface of the earth, and they are used to establish land maps and boundaries for ownership, location like building corners or the surface location of subsurface features, or other purposes.

An alternative definition, from the American Congress on Surveying and Mapping (ACSM), is the science and art of making all essential measurements to determine the relative position of points or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points or details.

The main principle of the surveying is working from whole to part.

Surveyors use tools such as total stations, robotic total stations, GPS receivers, prisms, 3D scanners, radios, handheld tablets, digital levels, and surveying software out of which we have used the total station to carry out the surveying.

TOTAL STATION

A total station or TST (total station theodolite) is an electronic/optical instrument used in modern surveying and building construction. The total station is an electronic theodolite (transit) integrated with an electronic distance meter (EDM) to read slope distances from the instrument to a particular point.

The various parts of the total station are shown below with the diagram:

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WORKNG PRINCPLE AND APPLICATION

Angle measurement

Most modern total station instruments measure angles by means of electro-optical scanning of extremely precise digital bar-codes etched on the rotating glass cylinders or discs within the instrument. The best quality total stations are capable of measuring angles to 0.5 arc-second. Inexpensive “construction grade” total stations can generally measure angles to 5 or 10 arc seconds.

Distance measurement

Measurement of distance is accomplished with a modulated microwave or infrared carrier signal, generated by a small solid-state emitter within the instrument’s optical path, and reflected by a prism reflector or the object under survey. The modulation pattern in the returning signal is read and interpreted by the computer in the total station. The distance is determined by emitting and receiving multiple frequencies, and determining the integer number of wavelengths to the target for each frequency. Most total stations use purpose-built glass corner cube prism reflectors for the EDM signal. A typical total station can measure distances with an accuracy of about 1.5 millimeters (0.0049 ft.) +2 parts per million over a distance of up to 1,500 meters (4,900 ft.).

Reflector less total stations can measure distances to any object that is reasonably light in color, up to a few hundred meters.

Coordinate measurement

Some total stations can measure the coordinates of an unknown point relative to a known coordinate. It can be determined using the total station as long as a direct line of sight can be established between two points. Angles and distances are measured from the total station to point under survey, and the coordinates(X, Y, and Z or easting, northing or elevation) of surveyed points relative to total station position are calculated using trigonometry and triangulation. To determine an absolute location a Total Station requires line of sight observations and must be set up over a known point or with line of sight to 2 or more points with known location.

For this reason, some total stations also have a Global Navigation Satellite System receiver and do not require a direct line of site to determine coordinates. However, GNSS measurements require longer occupation periods and offer poor accuracy in the vertical axis.

Data Processing

Some models include internal electronic data storage to record distance, horizontal angle, and vertical angle measured, while other models are equipped to write these measurements to an external data collector, such as a hand held computer.

When data is downloaded from a total station onto a computer, application software can be used to compute results and generate a map of the surveyed area. The generation of total stations can also show the map on the map on the touchscreen of the instrument right after measuring the points.

Topographic Surveying

Total stations are mainly used by land surveyors and civil engineers, either to record features as in topographic surveying or to set out features (such as roads, houses or boundaries). They are also used by archaeologists to record excavations and by police, crime scene investigators, private accident re-constructionists and insurance companies to take measurements of scenes. Meteorologists also use total stations to track weather balloons for determining upper-level winds.

Mining

Total stations are the primary survey instrument used in mining surveying.

A total station is used to record the absolute location of the tunnel walls, ceilings (backs), and floors as the drifts of an underground mine are driven. The recorded data are then downloaded into a CAD program, and compared to the designed layout of the tunnel.

Mechanical and Electrical Construction

Total stations have become the highest standard for most forms of construction layout.

It is most often used in the X and Y axis to layout the locations of penetrations out of the underground utilities into the foundation, between floors of a structure, as well as roofing penetrations.