DUMPY LEVEL

What is Dumpy Level?

Dumpy level is commonly used leveling instrument to locate the points in same horizontal plane. It is also called as automatic level or builder’s level. Elevations of different points and distance between the points of same elevation can be determined by dumpy level.

The telescope is fixed to its supports in dumpy level and hence it cannot be rotated in vertical axis. It is invented by William Gravatt in 1832.

Components of Dumpy Level

Dumpy level consists the following parts or components

• Telescope
• Bubble tubes
• Compass
• Vertical spindle
• Tribrach screws
• Foot screws
• Leveling head
• Tripod

Fig: Components of a Dumpy Level

Telescope

Telescope is used to observe the distant object through line of sight provided by its arrangement. In general, the telescope is fixed to the vertical spindle of dumpy level so that it can be rotated along with vertical spindle.

Parts of Telescope in Dumpy Level

The important parts of telescope are as follows

• Eye piece
• Objective lens
• Diaphragm
• Focusing screw
• Ray shade

Eye piece

Eye piece is used by the observer’s eye to view the distant object. It contains magnifying glass which magnify the observing image and also the cross hairs of diaphragm. So, accurate reading can be obtained. Erecting eyepiece is used to view the normal image which is generally inverted by objective lens.

Objective lens

Objective lens are provided at the other end of the telescope. The objective lens consists of two parts, the front part consists convex type lens and the back part consists concave lens. So, the image obtained from the objective lens is always inverted.

Diaphragm

Diaphragm is provided in front of the eye piece. It contains cross hairs made of dark metal which are arranged in perfect perpendicular positions. These cross hairs are used by the eye piece to bisect the objective through objective lens.

Focusing screw

Focusing screw is used to adjust the focus if cross hairs and the image clarity. The magnification of eye piece is managed by this focusing screw.

Ray shade

Ray shade is used to prevent the objective lens from sunlight or any other light rays which may cause disturbance to the line of sight.

Bubble tubes

Bubble tubes are provided to check the level of the instrument. Two bubble tubes are provided in a dumpy level which are arranged perpendicular to each other on the top of the telescope. One tube is called as longitudinal bubble tube and another is called as cross bubble tube. The instrument is said to be in perfect position when both the bubbles of the tubes are at center or middle of the tube.

Compass

Compass is used to determine the magnetic bearing of line. In case of dumpy level, circular compass is provided just under the telescope. The compass contains a pointer in it and readings are marked inside it. The pointer is set to zero when it faces the north line from which the magnetic bearings are measured.

Vertical spindle

Vertical spindle is located at the center of the whole instrument. The telescope can be rotated in horizontal direction with respect to vertical spindle. The instrument is connected to the tripod stand using vertical spindle.

Tribrach

Tribrach plate is parallel to the leveling head or trivet. It is connected to trivet by leveling screws or foot screws which can adjust the tribrach plate. The horizontal level of the instrument can be achieved by adjusting this tribrach plate.

Foot screws

Foot screws are provided to regulate the tribrach position and hence the instrument can be leveled which is known by observing the bubble tube. The tribrach plates can be lowered or raised using foot screws. The position of tribrach is said to be correct when the bubble in bubble tube is at center.

Leveling head

Leveling head is also called as trivet. It contains two triangular shaped plates which are arranged parallel to each other. Three groves are provided at the three corners of the plates in which foot screws are supported.

Tripod

Tripod is used to support the whole leveling instrument on its top. It consists three legs which can be adjustable to required position. The legs are of same height and they may be solid or hollow. Steel shoes are provided at the bottom of each leg to hold the ground in a fixed position.

Procedure of Dumpy Level Surveying

The procedure of dumpy level surveying starts with some temporary adjustments which are:

• Setting up of instrument
• Leveling up
• Focusing

Setting up of Dumpy Level

The instrument is fixed to the tripod stand using clamp screws. Spread the tripod legs and position the instrument at convenient height. Firstly fix the two legs in the ground at a point and centering of bubble in the bubble tubes is done by adjusting third leg.

Leveling up

The leveling up of an instrument is done using foot screws or leveling screws. In this case, the telescope is arranged parallel to the any two leveling screws and the bubble in the tube is centered by turning both the screws either inwards or outwards.

When it is centered, then the telescope is turned 90o and the third screw is turned until the bubble come to center. Repeat the process until the bubble in the tube always stays at the middle in any position of telescope.

Focusing

Focusing is done by adjusting eye piece and focusing screw. Eye piece is adjusted until the cross hairs of diaphragm are clearly visible. To eliminate the parallax error, a white paper is used to obtain sharp vision of cross hairs.

Focusing screw is adjusted to view the clear image of the objective or staff. Focusing is said to be done when the cross hairs bisect the objective or staff with clear vision.

After completion the above temporary adjustments, now it’s time to take levels of required positions or points. The telescope is rotated towards the line of objective or staff and bisect it. The levels are noted at different points which values are decided from a known bench mark point in that area. The details are tabulated as below.

Position observed	Level reading	HCR (higher cross hair reading)	LCR (lower cross hair reading)	(HCR-LCR) x 100	Distance of point from instrument	Remarks / Error
1
2
3

Benefits of Dumpy Level Surveying

• Dumpy level is easy to use.
• Adjustments can be made as per the requirement on any type of ground.
• Level readings are very accurate in case of dumpy level.
• Optical power is high for dumpy level.
• Price of dumpy level is cheap when compared to other instruments.

Drawbacks of Dumpy Level Surveying

• It is limited to only horizontal angle measurement.
• The angles obtained by dumpy are not that accurate.

WHAT IS TOTAL STATION ?

WHAT IS TOTAL STATION ?

May 29, 2019

A total station is an electronic/optical instrument used in modern surveying and building construction that uses electronic transit theodolite in conjunction with electronic distance meter (EDM).It is also integrated with microprocessor, electronic data collector and storage system.

The instrument is used to measure sloping distance of object to the instrument, horizontal angles and vertical angles. This Microprocessor unit enables for computation of data collected to further calculate the horizontal distance, coordinates of a point and reduced level of point.

Data collected from total station can be downloaded into computer/laptops for further processing of information.

Total stations are mainly used by land surveyors and civil engineers, either to record features as in topographic surveying or to set osut features (such as roads, houses or boundaries). They are also used by archaeologists to record excavations and by police, crime scene investigators, private accident Reconstructionist and insurance companies to take measurements of scenes. 

Capability of a Total Station

Microprocessor unit in total station processes the data collected to compute:

1. Average of multiple angles measured.
2. Average of multiple distance measured.
3. Horizontal distance.
4. Distance between any two points.
5. Elevation of objects and
6. All the three coordinates of the observed points.

Data collected and processed in a Total Station can be downloaded to computers for further processing.

Total station is a compact instrument and weighs 50 to 55 N. A person can easily carry it to the field. Total stations with different accuracy, in angle measurement and different range of measurements are available in the market. Figure below shows one such instrument manufactured by SOKKIA Co. Ltd. Tokyo, Japan.

                                                     Fig: Parts of total station

Important Operations of Total Station

Distance Measurement

Electronic distance measuring (EDM) instrument is a major part of total station. Its range varies from 2.8 km to 4.2 km. The accuracy of measurement varies from 5 mm to 10 mm per km measurement. They are used with automatic target recognizer. The distance measured is always sloping distance from instrument to the object.

Angle Measurements

The electronic theodolite part of total station is used for measuring vertical and horizontal angle. For measurement of horizontal angles any convenient direction may be taken as reference direction. For vertical angle measurement vertical upward (zenith) direction is taken as reference direction. The accuracy of angle measurement varies from 2 to 6 seconds.

Data Processing

This instrument is provided with an inbuilt microprocessor. The microprocessor averages multiple observations. With the help of slope distance and vertical and horizontal angles measured, when height of axis of instrument and targets are supplied, the microprocessor computes the horizontal distance and X, Y, Z coordinates.

The processor is capable of applying temperature and pressure corrections to the measurements, if atmospheric temperature and pressures are supplied.

Display

Electronic display unit is capable of displaying various values when respective keys are pressed. The system is capable of displaying horizontal distance, vertical distance, horizontal and vertical angles, difference in elevations of two observed points and all the three coordinates of the observed points.

Electronic Book

Each point data can be stored in an electronic note book (like compact disc). The capacity of electronic note book varies from 2000 points to 4000 points data. Surveyor can unload the data stored in note book to computer and reuse the note book.

Uses of Total Station

The total station instrument is mounted on a tripod and is levelled by operating levelling screws. Within a small range instrument is capable of adjusting itself to the level position. Then vertical and horizontal reference directions are indexed using onboard keys.

It is possible to set required units for distance, temperature and pressure (FPS or SI). Surveyor can select measurement mode like fine, coarse, single or repeated.

When target is sighted, horizontal and vertical angles as well as sloping distances are measured and by pressing appropriate keys they are recorded along with point number. Heights of instrument and targets can be keyed in after measuring them with tapes. Then processor computes various information about the point and displays on screen.

This information is also stored in the electronic notebook. At the end of the day or whenever electronic note book is full, the information stored is downloaded to computers.

The point data downloaded to the computer can be used for further processing. There are software like auto civil and auto plotter clubbed with AutoCad which can be used for plotting contours at any specified interval and for plotting cross-section along any specified line.

Advantages of Using Total Stations

The following are some of the major advantages of using total station over the conventional surveying instruments:

1. Field work is carried out very fast.
2. Accuracy of measurement is high.
3. Manual errors involved in reading and recording are eliminated.
4. Calculation of coordinates is very fast and accurate. Even corrections for temperature and pressure are automatically made.
5. Computers can be employed for map making and plotting contour and cross-sections. Contour intervals and scales can be changed in no time.

However, surveyor  should check the working condition of the instruments before using. For this standard points may be located near survey office and before taking out instrument for field work, its working is checked by observing those standard points from the specified instrument station.

Read More:

Modern Surveying Instruments and Their Uses

What is Contour Interval? Its Calculation, Uses and When it is Required

Electronic Distance Measurement Instrument- Types, Functions & Operations

Roles and Work of Surveyor in Construction

CIVIL ENGINEERING FACTS

If you’re interested in a civil engineering career, you may not know that this science is as old as the hills, yet as young as the 18th century. Additionally, there are at least ten sub-disciplines within this field that range from engineering buildings to sea walls to roller coasters and to water slides. If you’ve ever marveled at the Hoover Dam or the Empire State Building, then you’ve witnessed the technology, design and science of civil engineering. This list provides 35 fundamental facts about this career, its diversity and its engineering wonders.

About Civil Engineering

1. Until modern times there was no clear distinction between civil engineering and architecture, and the terms engineer and architectoften referred to the same person until the 18th century.


2. In the 18th century, the term “civil engineering” came into use to describe engineering work that was performed by civilians for nonmilitary purposes.


3. The first self-proclaimed civil engineer was John Smeaton who constructed the Eddystone Lighthouse.


4. Civil engineers frequently work on complex projects which involve many technical, economic, social and environmental factors.


5. Civil engineering takes place on all levels: in the public sector from municipal through to national governments, and in the private sector from individual homeowners through to international companies.


6. Civil engineers also help to preserve the environment by assisting in the cleaning up of existing pollution and planning ways to reduce future pollution of air, land and water.


7. The first private college to teach Civil Engineering in the United States was Norwich University, Vermont, founded in 1819 by Captain Alden Partridge.


8. The first degree in Civil Engineering in the United States was awarded by Rensselaer Polytechnic Institute in 1835.


9. The first civil engineering degree to be awarded to a woman was granted by Cornell University to Nora Stanton Blatch in 1905.


10. The Institution of Civil Engineers (ICE) was founded in a coffee shop in London in 1818 by eight young civil engineers, the youngest was 19.


11. The American Society of Civil Engineers (ASCE) was founded in 1852. It is the oldest national engineering society in the United States.


12. All 50 States and the District of Columbia require licensure for engineers who offer their services directly to the public.


13. According to a 2009 survey, people with a bachelor’s degree in civil engineering started at $52,048 a year on average.

Civil Engineering Sub-Disciplines

14. Coastal engineering is concerned with managing coastal areas. The term coastal defense is the more traditional term, but coastal management has become more popular as the field has expanded to include techniques that allow erosion to claim land.


15. Construction engineering involves planning and execution of the designs from transportation, site development, hydraulic, environmental, structural and geotechnical engineers.


16. Earthquake engineering is dedicated to reducing earthquake risk by advancing the practice of this science.


17. Environmental engineering can be involved with pollution reduction, green engineering, and industrial ecology and involves protecting the environment and human health.


18. Geotechnical engineering is an area of civil engineering concerned with the rock and soil that supports civil engineering projects.
19. Materials engineering and sciences deals with materials such as concrete, mix asphalt concrete, metals as well as paints and finishes.


20. Municipal or urban engineering involves specifying, designing, constructing, and maintaining streets, sidewalks, water supply networks, sewers, street lighting, municipal solid waste management and disposal, storage depots for various bulk materials used for maintenance and public works, public parks and bicycle paths.


21. Structural engineering is concerned with designing structures to be safe and serviceable for their users


22. Transportation engineering is concerned with moving people and goods efficiently, safely, and in a manner conducive to a vibrant community.


23. Water resources engineering is a discipline that combines hydrology, environmental science, meteorology, geology, conservation, and resource management.

Civil Engineering Feats

24. The longest street in the world is Toronto’s Yonge Street, listed as 1,178 miles (1,896 km) in length — roughly the distance from San Diego, California, to Seattle, Washington.


25. A civil engineer created the slippery part of the water slide. Without the right flow of water, there is no ride.


26. The Channel Tunnel is one of the greatest civil engineering projects of the 20th century, has an ultimate design capacity of 600 trains per day each way under the English Channel.


27. The Akashi-Kaikyo Bridge, also known as the Pearl Bridge, has the longest central span of any suspension bridge. The central span is a staggering 1,991 meters, or 6,532 ft.


28. It took a century to overcome deep waters, strong winds, and high chance of earthquakes to build the Rion-Antirion Bridge. Completed in 2004, it spans the Gulf of Corinth and won an Outstanding Civil Engineering Achievement award.


29. The Itaipu Dam, located at the Brazilian-Paraguayan border, is the largest operating hydroelectric facility in terms of annual generating capacity.


30. The Golden Gate Bridge is one of the longest suspension bridges in the world and has become an internationally recognized symbol of San Francisco and California.


31. The Empire State Building was built in just 18 months during the Great Depression and was one of the first to employ the then new fast track construction technique. Following the destruction of the World Trade Center in 2001, the Empire State Building again became the tallest building in New York City and New York State.


32. the Hoover Dam, standing 726.4 feet high, is one of the tallest concrete dams ever built and created one of the largest man-made lakes in the U.S.


33. The Burj Al Arab is a 5-star luxury hotel located in Dubai, United Arab Emirates. At 321 m (1,053 ft), it is the fourth tallest hotel in the world. The shape of the structure is designed to mimic the sail of a ship.


34. The Netherlands North Sea Protection Works is a marvel of coastal engineering created to protect a large area of land around the Rhine-Meuse-Scheldt delta from the sea.


35. The Millennium Force Roller Coaster in Sandusky, Ohio, is the world’s tallest (310 feet) and fastest (92 mph) roller coaster, and is supported by 226 footers using 9,400 yards of concrete. It took 175 truckloads of steel to create the frame.