Dumpy Level Surveying, About, Components, Advantages & Limitations
About Dump Level Instrument:-
The Dumpy level is an instrument used for surveying and levelling operations. It comprises of a telescope tube, firmly held between two collars and adjusting screws. the entire instrument is staged by the vertical spindle.
The telescope placed on the Dumpy level are often rotated amongst the horizontal plane. Relative elevation of survey points on the land are often determined through the Dumpy level .
The Dumpy level was invented by Willian Gravatt, in 1832. Being a engineer , he invented the Dumpy level while using Y (Wye) level instrument.
Principle of Dumpy level Instrument:
The Dumpy level operates on the principle by establishing a visible relationship between two or more points, through an inbuilt telescope and a bubble level. The desirable level of accuracy are often achieved through steps.
It is also called through various names like Surveyors levels, Builders level, Dumpy level or maybe its pre-historic version “Y(Wye) Level”.
Accuracy of Dumpy level over other levelling instruments:
The prime reason for using Dumpy level over other levelling instruments is its accuracy.
A Dumpy level is understood for top accuracy values for many of the Tacheometric methods. The accuracy of a Dumpy level are often within 1:4000 for each 100 m.
Use of Dumpy level in Surveying:
Dumpy level holds significant importance within the surveying of a construction site. the extent of accuracy and handiness of Dumpy level has made it a prominent choice amongst surveyors.
The prime reason for performing levelling on a construction site is to form the sector level and even.
To determine the differences tall between two points.
To measure the peak and distance of various locations of surveying land through the principle of relativity.
To measure following distance amongst various point on the surveying land.
Setting out levels and inclined surfaces for construction.
To draw contours ashore .
Important Components of Dumpy level:
Dumpy Level Components
Parts of Dumpy level
1. Telescope:-
The telescope is employed to live distant objects within the line of sight. The telescope is usually connected with vertical spindle, facilitating telescope to be movable in various directions.
Telescope comprises of varied parts, all the parts are described below.
Eye Piece:
It comprises of a hand glass and is primarily employed by the observer.
Objective Piece: it's placed at the farther end of eyepiece. It comprises a converging lens and a diverging lens
.
Diaphragm:
Provided within the outline of the eyepiece with the cross of dark metal. they're provided to bisect object.
Focusing Screw: they're meant to align the main target and image clarity of the thing .
Ray Shade: Prevents sunlight from entering the target lens.
2. Bubble Tubes
They are provided to align the extent of instrument. Provided by bubble tubes on horizontal and vertical direction. The instrument is prepared to survey when both the bubbles are within the centre.
3. Compass
It is wont to determine the magnetic bearing of the road of the trail of the survey. The compass comprises of pointer on marking of directions. The compass is aligned for the magnetic bearing within the north direction.
4. Vertical Spindle
Located at the centre of the instrument. It helps the telescope to rotate within the vertical direction. Vertical Spindle is supposed to be a conjunction point between tripod and telescope.
5. Tribrach
It is parallel to the levelling head and primarily utilized to regulate the horizontal level of the instrument. The trivet is connected through foot screws. Tribrach in Dumpy Level
6. Foot Screws
The foot screws are wont to calibrate the instrument through the bubble tube. Adjusting foot screws one can calibrate tribrach plate. to make sure the bubble is at the centre, foot screws are operated.
7. Levelling Head
Also referred to as a trivet, it comprises of two triangular plates aligned parallel to every other. Comprises of groves to carry foot screws.
8. Tripod
Tripod is that the supporting medium of the entire Dumpy level . Comprising of three legs made from hollow steel sections or light or hardwood. Steel shoes provided at the foot ensures that the tripod is immobile with slight jerks.
Tripod for Dumpy level
The procedure of surveying on Dumpy Level:
The step by step procedure to perform the surveying using Dumpy level . Survey through a Dumpy level are often easily conducted over a site. The Dumpy level may be a two-man procedure, one may require a minimum of an assistant to proceed with the operation. Below listed sorts of equipment are the one that one requires to initiate the surveying operation.
Dumpy Level
Tripod with foot screws.
E-meter Staff/ English Staff
Once the above instruments are available, the surveying operation can proceed. Following steps must be followed to finish with the surveying operation.
Setup a Benchmark [BM]:-
The process of surveying starts from a specified benchmark with already known height concerning Mean water level (MSL). This previous data of benchmark are often acquired from previous surveys. Benchmark data is typically found on churches, govt buildings, municipal offices, railroad station boards, etc. If data isn't available, one may choose an arbitrary point (temporary benchmark like fence post etc) with an assumed height. You can search the benchmarks of your location from here Railway Board for Benchmark
In the above Railway Board, you'll see Mean water level is mentioned.
Location and Position of Dumpy level:
Select an area where you've got a transparent sight of the benchmark. it's recommended to line up the instrument within the centre of the land where you'll see all the location including benchmark.
Setting up Dumpy level on Tripod:-
The Tripod has got to be placed firmly on the bottom in order that it can efficiently hold the Dumpy level . generally , the tripod height must be adjusted up till eyesight.
The reduced level is that the difference of Height of the instrument and Foresight reading.