LAB Report ( Levelling 1- Temporary Benchmark) PDF

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This report is about Levelling 1 - Temporary Benchmark...

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FACULTY OF ENGINEERING DEPARTMENT OF CIVIL ENGINEERING ECV3511 GEOMATICS ENGINEERING SEMESTER 1 2021/2022 LAB TITLE: LEVELLING 1 – TEMPORARY BENCH MARK GROUP NO: 2F

Format Report (Group) MARKS Front Page 5 Introduction

GROUP MEMBERS:

10 Objective

No

Matric Number

1

206537

ABDUL HAKIM BIN ABDUL HAMID

5 Methodology

2

207495

AHMAD KAMAL ARIF BIN SUHAIMI

10 Results & Calculation

3

208075

NUR AMELIYA BINTI A.WAHAB

20 Discussion

4

207221

ADELLINNE NATASYA BINTI ROSDI

25 Conclusion

5

205641

HARIVARMAN RAJ A/L RAJINIKANTH

Name

10 Equipment

10 Appendices & Effort 5 Total

NAME OF LECTURER: SR. GS. DR. SITI NUR ALIAA ROSLAN ASSISTANT ENGINEER: MR. WAN ZAKARIA WAN YUSOFF TEACHING ASSISTANT: MDM. NURUL SUHADA MOHAMAD BASIR DATE OF SUBMISSION: 24/11/2021

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TABLE OF CONTENTS INTRODUCTION ........................................................................................................................................ 1 OBJECTIVES ............................................................................................................................................. 2 APPARATUS.............................................................................................................................................. 2 Table 1 shows List of apparatus and its function.............................................................................. 3 METHODOLOGY ....................................................................................................................................... 4 Figure 1 shows Procedure of Levelling 1 – Temporary Benchmark ............................................. 4 RECOMMENDATIONS ............................................................................................................................. 5 RESULT ...................................................................................................................................................... 5 Table 2 shows Results on levelling test ............................................................................................. 5 CALCULATION.......................................................................................................................................... 6 DISCUSSION .............................................................................................................................................. 6 CONCLUSION............................................................................................................................................ 7 REFERENCES ........................................................................................................................................... 8 APPENDICES............................................................................................................................................. 8 Table 3 shows Pictures and descriptions of group members running the experiment ............... 9 Figure 2 shows Raw Data .................................................................................................................... 9

INTRODUCTION Levelling is known as a measurement process that determines the height differences between two or more points. Levelling can be carried out by using an auto level which is usually set on a tripod and used together with staff. There are few terms that are commonly used in levelling including backsight (BS), foresight (FS), intermediate sight (IS), bench mark (BM), and temporary bench mark (TBM). The initial reading from a new instrument station is defined as backsight (BS), while on the contrary, foresight (FS) is the last reading from the current instrument station. Any sighting that is not a BS or FS is referred as intermediate sight (IS). A benchmark (BM) is a permanent reference point with an arbitrary height ascribed to it or which its height has been accurately measured via levelling. Most surveys and construction work require the heights of various BMs to be established throughout a site, and these are known as temporary benchmark (TBM).

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First, the height of the benchmark and distance of the reference point for this Levelling 1 must be measured. Then, to set a closed loop, we can go on to the new temporary benchmark and back to the first point. Once all the data has been collected, several calculations can be performed to determine the value of misclosure. The misclosure formula is as follows: Misclosure = ∆Hknown - ∆Hmeasured where, ∆Hknown = known height ∆Hmeasured = measured height The misclosure should be equal of less than the value of 12√k. The formula below can be used to determine whether the misclosure obtained is acceptable or not: Misclosure ≤ 12√k where, k = length of the loop

OBJECTIVES •

To find the elevation of given point with respect to datum

•

To determine the relative height of the surface of the earth

•

To know the reduce level of different point

APPARATUS NAME

FUNCTION

Tripod

To give support and height for

PICTURE

Auto Level

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Staff

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To determine the height or distance of the points.

Bubble staff

To make sure the staff is centred and straight from the ground.

To make sure the reading is accurate.

Auto level

To measure the height and verify points on levelling staff.

Measuring tape

To measure the distance between the points.

Table 1 shows List of apparatus and its function

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METHODOLOGY

All the instruments were setting up. Make sure that, the bubble staff was attached to the staff and used to stabilize the staff.

A graduated staff was read through the automatic level. The elevation of points can be established by first reading the staff on benchmark.

The staff is then moved to the desired point, the level is turned and the staff is read again.

The reading at the benchmark is called the backsight (BS). The reading taken after turning the instrument and moving the staff is the foresight (FS).

To continue levelling, the staff is kept on the point at A and the instrument moved to the midpoint between A and the next point B. A is called change point (CP) or turning point (TP)

Staff A is carefully turned toward the instrument and a BS reading taken.

Then the staff is move to B and a FS reading is made. The procedure is repeated as many times as needed. The levelling should always end on a BM as a check. Figure 1 shows Procedure of Levelling 1 – Temporary Benchmark

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RECOMMENDATIONS •

Hold the staff steadily and make sure the staff bubble is at the center area

•

Observe the reading on staff multiple times before recording the data

•

Make sure the bubbles are properly level

•

Make sure the person setting up the level is the one who will observe the staff

•

Ensure the staff is not too far away from the auto level.

RESULT

BS

IS

FS

Rise

Fall

1.490

Height

Remarks

50.000

TBM

1.376

1.749

0.259

49.741

CP1

1.731

1.480

0.104

49.637

CP2

0.750

0.709

50.659

CP3

50.000

TBM

1.022

1.409 5.347

5.347

0.659 1.022

1.022

Σ, Total

50.000 - 50.000 5.347 - 5.347 = 0.000

1.022 - 1.022 = 0.000 = 0.000

△

Table 2 shows Results on levelling test

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CALCULATION Obtained misclosure: 0.000 mm Allowable misclosure: ±5√n Where n is the number of changing points n=4

Allowable misclosure = ±5√4 = ± 10 mm Therefore, the obtained misclosure is acceptable as it is in the range of ± 10 mm.

DISCUSSION Levelling is a measurement technique used to determine the height differences between two or more points. A tripod, staff, bubble staff, auto level, and measuring tape can be used to level a surface. Backsight (BS) and foresight (FS) readings must be collected and recorded for each changing point (CP). Before we do the levelling process, we must do the Two-Peg Test. The two-peg test is used to ensure that the line of sight is providing an accurate reading and to determine how much adjustment is required. This should be done on a regular basis by the installer to ensure that the instrument is properly levelled and provides accurate readings. For the first part, after subtracting the difference between first point (1.421m) and second point (1.462m), we got the value -0.041m and for the second part, we subtracted the first point (1.471m) and the second point (1.510m), and we got the value for second part which is -0.039m. From the result that we calculated, the range that we got is -2mm, this result is within the allowable range therefore it is acceptable and can be used for the levelling process. In our levelling process, we collected and calculated all the Auto Level readings which are the Backsight (BS), the Foresight (FS), Rise, Fall, Height (Reduce Level) and Remarks and entered them into the Levelling Form. We did not include the Intermediate Sight (IS) in Levelling Form. The levelling process begins at Temporary Benchmark (TBM 50.000m) where we obtained the value for Backsight (BS) and we got the value for Foresight (FS) at Changing point 6

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1 (CP1). This process is repeated for 4 setups and 4 checkpoints and make sure it ended back to Temporary Bench Mark (TBM 50.000m) to retain the value Foresight (FS) to create a sample loop. After that, we computed the difference between Backside (BS) and Foresight (FS), Rise and Fall, and the Reduce Level for that may have happened during the levelling process. The allowable misclosure can be calculated using the formula of ±5√n where n is the number of changing points. The result that was obtained from the calculation is 0mm for each of the summation of difference. This indicated that our results for misclosure is acceptable since it is within the range of ± 10 mm and our levelling process is completed. If however the misclosure exceed the limit of allowable misclosure, the levelling process needs to be repeated from start to finish. Error can always occur during the levelling process including careless instrument usage, where the instrument should be precisely levelled, and the hand should not rest on the telescope or tripod while obtaining all the data. If this not done precisely, inaccuracy and error will occur. After that, error due to sluggish bubble. When the bubble is sluggish, it will come to rest in the wrong position, though it could creep back to the correct position while the sight is being taken. However, observing the bubble after the target has been sighted may help to mitigate the error. The error is attempting to compensate. Another common blunder is incorrectly holding the staff (not vertically). This will affect the reading because of the staff not held in an absolutely vertical position. This error is much more visible for larger staff because of the bigger scale of the staff. Therefore, the staff must be in a perfectly vertical position so the error will not occur.

CONCLUSION The purpose of levelling is to determine the height difference between two points in a given area. The primary goal of levelling is to construct roadways, railroads, sewers, and water supply systems, as well as to establish grade lines on existing topography. Furthermore, levelling can be used to lay out the construction barriers in accordance with the anticipated elevations. A levelling staff, tripod, auto level meter, staff bubble, and measuring tape are all required for levelling. As a result of this levelling experiment, we were able to successfully set a new temporary benchmark. The data obtained has the least amount of error, and the measurements taken are close to being accurate.

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REFERENCES Jim, A. (n.d.). Inteller. Retrieved from Two-Peg Test: How to Determine the Accuracy of Your Levelling Instruments: https://www.onsiteinstaller.com/online_exclusives/2019/04/two-peg-test-how-todetermine-the-accuracy-of-your-leveling-instruments John, U., & Bill, P. (2010). Surveying for engineers. England: Palgrave Macmillan. Kreisle, & WIlliam, E. (1998). History of Engineering Survering. Surveying Engineering, 102-124. Rajput, K. (n.d.). CivilJungle. Retrieved from Instrumental Errors in Levelling: https://civiljungle.com/instrumental-errors-in-leveling/

APPENDICES PICTURE

DESCRIPTION Setting up the instruments.

Measuring the distance for two-peg test.

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Observing the reading of height on the staff using the auto level.

Table 3 shows Pictures and descriptions of group members running the experiment

Figure 2 shows Raw Data

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