What is dumpy level in construction?

An optical tool for levelling and surveying tasks is the dumpy level. The dumpy level, also known as a builder’s level or an automated level, is a typical levelling tool used to identify points in the same horizontal plane.  Included in it is a telescopic tube that is securely fastened using two collars and adjustable screws. The vertical spindle stages the entire instrument.

The telescope may be spun around the horizontal plane when it is positioned on the dumpy level. The dumpy level can be used to calculate the relative height of survey stations on the ground.

Willian Gravatt created the dumpy level in 1832. He created the dumpy level using a Y (Wye) level instrument because he was a civil engineer.

Why is it called dumpy level?

Previously known as Gravatt’s Level, the optical tool got the name dumpy level owing to its compact nature. Using the dumpy level, one can determine, elevations of different points and also distance between points of same elevation.

How does a dumpy level work?

The workings of a dumpy level instrument are based on the idea that two or more points may be visually related to one another using a bubble level and an integrated telescope. Steps can be taken to reach the desired degree of precision.

It is also known by a number of other names, including Surveyors levels, Builders levels, Dumpy levels, and even by its prehistoric name, “Y(Wye) Level.”

What is the accuracy of a dumpy level?

The accuracy of the dumpy level is the main justification for using it instead of other levelling tools.

The majority of tacheometric algorithms have good accuracy values at a dumpy level. A dumpy level can be accurate to within 1:4000 for every 100 metres.

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Dumpy level: Use of dumpy levels in surveying

The use of dumpy levels is crucial while surveying a building site. Dumpy levels are a popular option for surveyors due to their accuracy and portability.

•  Making the field level and even is the main goal of levelling on a building site.
•  To calculate the height disparities between two places.
•  To use the relativity principle to calculate the height and distance of various surveying locations.
•  To measure the distance between the following points on the surveying land.
•  Preparing sloped and level areas for building.
•  To plot land contours.

Dumpy level: Components

Telescope

The telescope measures far-off things that are in the line of sight. The telescope is often attached to a vertical spindle, allowing for easy movement in different directions.

The numerous components that make up a telescope are all listed here.

•       Eyepiece: Mainly utilised by the observer, it consists of a magnifying glass.
•       At the further end of the eyepiece lies the objective piece. It has both convex and concave lenses.
•       Diaphragm: A black metal cross is provided in the eyepiece’s outline. They are offered to divide a thing.
•       Focusing screw: These are used to align the object’s focus and visual sharpness.
•       Ray shade: Prevents the objective lens from being damaged by sunshine.

Bubble tubes

They are offered to align the instrument’s level, provided in both a horizontal and vertical direction by bubble tubes. When both bubbles are in the centre, the device is prepared to survey.

Compass

It is employed to ascertain the magnetic bearing of the survey line’s course. The compass has a pointer for indicating directions. The compass is set up to take a magnetic heading northward.

Spindle that is vertical

The telescope benefits from rotating vertically. A conjunction point between a tripod and a telescope is intended to be at the vertical spindle.

Tribrach

It is used largely to regulate the instrument’s horizontal level and runs parallel to the levelling head. Foot screws hold the tribrach in place.

Foot screws

Through the bubble tube, the foot screws are utilised to calibrate the instrument. Tribrach plate calibration is done by adjusting the foot screws. Foot screws are turned to make sure the bubble is in the centre.

Levelling head

Another name for a trivet is the levelling head, which consists of two triangular plates that are parallel to one another and have grooves for holding foot screws.

Tripod

The entire dumpy level supporting medium is a tripod consisting of three legs made of light or hardwood, hollow steel pieces, or both. The tripod is kept motionless with only mild jerks thanks to the steel soles that are given at the foot.

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Dumpy level: How to conduct a survey?

A site’s survey through a low level can be completed with ease. The dumpy level is a two-man job; to complete it, one may need at least a helper. The sorts of equipment that are needed to start the surveying activity are given below.

•       Foot screws on a shoddy level tripod.
•       English staff and e-meter staff

The surveying operation can start as soon as the aforementioned instruments are available. To finish the surveying procedure, the following actions must be taken.

Establish a benchmark (BM)

The surveying method begins at a predetermined baseline whose height in relation to Mean Sea Level (MSL) is already known. This benchmark’s historical data may be found in earlier surveys. Typical examples of benchmark data are churches, governmental structures, municipal buildings, railroad station boards, etc. In the absence of data, one may select a random point (a temporary benchmark like a fence post or other object) with an assumed height.

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Location and position of the dumpy level

Pick a spot where you can see the benchmark well. The instrument should be placed in the middle of the area so that you can view the entire location, including the benchmark.

Setting up a dumpy level on a tripod

The tripod needs to be firmly planted on the ground in order to hold the dumpy level in place. Generally speaking, the tripod height has to be set to eye level. The tripod stand’s legs must be sufficiently broad to support the instrument and must be firmly planted in the ground.

The tripod stand’s foot screws must be used to firmly and securely fasten the dumpy level to the stand. Make sure the equipment is securely fastened using a tripod. Special care should be given while handling the level head due to its extreme sensitivity and high cost.

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Readings and observations

–        Backsight [BS] reading

The surveyor must do a backsight reading as their initial reading. You can determine the instrument’s height with the use of backsight reading. We can move forward with more foresight-level readings thanks to these two readings. The staff should be held “vertically” on the benchmark by the second guy (helper). 

The surveying process is started by the operator looking through the telescope’s eyepiece and rotating the dump level until the crosshairs are aligned with the E staff. Then look closely and pay attention to the figures on E Staff. Both metric and imperial measures are used on the crew. The staff’s “E” marking represents 5 cm on a metric scale.

–        Height of the level (H.L.) or height of the instrument (H.I.)

You need to know the height of the backsight, which we observed in the previous stage, to determine the height of the level. The instrument’s height will be determined by adding the benchmark height to the backsight height.

–        Readings of the foresight

You are now prepared to start the foresight readings after determining the instrument’s height. Find and mark the A, B, and C locations on the ground where you want to determine the level. The E Staff should be placed on the desired point (let’s say “A”) and held vertically. Repeat the process we used to determine the backsight height for getting readings from the E Staff.

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Dumpy level: Safety precautions

The dumpy level is all about levels. While using the device, appropriate safety measures should be implemented. Otherwise, the instrument will outperform itself and produce false findings.

•  To reach eye level, the tripod must be adjusted.
•  Aim to keep your hands off the tripod and never put pressure or contact on it while moving.
•  Make sure you watch out for the tripod’s legs when moving around it.
•  Continue inspecting the bubble; even a tiny change might provide erroneous results.
•  Never place the instrument on soft ground.

Dumpy level: Benefits

• Dumpy level is very easy to use
• One can make any kind of adjustment on any ground using the dumpy level
• Dumpy level is cost effective and readings are very accurate
• Dumpy level optical power is very high

 

Dumpy level: Disadvantages

• The angles achieved by dumpy level are not very accurate.
• It is restricted to only horizontal angle measurement.

 

Using dumpy level: Tips to remember

Handling the surveying equipment requires careful attention to ensure proper functioning and longevity. Here are some guidelines:

Staff handling

• In windy conditions, stabilise the staff to keep it vertical and steady.
• Avoid using the fully-extended staff near overhead power cables.
• Pull out (and return) the sections one at a time to maintain stability.
• Store the staff in its sleeve after each use.
• Keep mud and grit off the staff to prevent scratching the painted markings.
• After a survey, dampen the supplied microfiber cloth and wipe off each section of the staff as it is closed up.

Level head care

• The level head is a precision instrument; handle it with care.
• When not in use, store the level head in its designated box.
• In rainy conditions, cover the level head with a bag or rain hood, or preferably unscrew the head and place it in its box.
• If the level head gets wet, ensure it dries completely before returning it to the box to prevent fogging and potential internal damage.

Survey completion

• After completing the survey, unscrew the level head carefully and place it in its correct position within the box.
• Close the box lid securely.

Box handling

Avoid dropping the box containing the level head. Report any accidental kicks or drops to the Jigsaw team promptly, as it may require calibration or repair.

Tripod care

• Undo the catches on the tripod legs carefully.
• Retract the legs and clamp the catches back in place.
• Fasten the belt securely.
• Ensure the tripod remains free from dents or damage to maintain its usability.

 

Housing.com POV

A dumpy level serves as an essential tool in construction and surveying activities, facilitating accurate measurements of height differences and establishing horizontal levels. Its name derives from its compact design and ease of use. While it is not a theodolite, its simplicity and accuracy make it a preferred choice for many professionals. The dumpy level offers advantages such as ease of use, cost-effectiveness, and accurate readings, making it indispensable in various engineering applications. However, it does have limitations, particularly in measuring horizontal angles exclusively. Despite these limitations, proper handling and maintenance ensure its longevity and reliability in the field of surveying and construction. 

 

FAQs

What is dumpy level used for?

A dumpy level is primarily used in surveying and construction to measure height differences and establish horizontal levels. It aids in determining the elevation or height of points on the ground relative to a reference point, facilitating accurate construction and land development.

Why is it called dumpy level?

The term ‘dumpy level’ originates from its design characteristics. The instrument typically has a short and stout appearance, with a ‘dumpy’ or squat shape. This compact design, coupled with its simplicity and ease of use, led to the name ‘dumpy level’.

Is a dumpy level a theodolite?

No, a dumpy level is not a theodolite. While both instruments are used in surveying, they serve different purposes. A dumpy level is specifically designed for measuring height differences and establishing horizontal levels, whereas a theodolite is used for measuring angles both horizontally and vertically.

What is the advantage of a dumpy level?

The primary advantage of a dumpy level is its simplicity and ease of use. It provides accurate measurements of height differences and horizontal levels, making it invaluable in construction, land surveying, and various engineering applications. Additionally, dumpy levels are relatively robust and cost-effective, making them accessible to a wide range of professionals in the field.

What is the formula for figuring out the instrument's height?

Bench Mark (BM) height + Backsight Reading = the level's height.

Does the use of the dumpy level instrument have any limitations?

Despite being such a flexible tool, the dumpy level is only useful for measuring horizontal angles.