REPORT LEVELLING

ENGINEERING SURVEY LEVELLING

1.0 )

Introduction

Levelling Levelling is is a method to measure the elevation difference between two (2) or more points. In this practical, practical, focus is is shifted to one of levelling levelling technique techniquess namely , fly level level observation or observation or also known as the rise and fall method . The observation will be initiated from a known reduced level (RL) (RL) value of a benchmark benchmark (BM) and end end at another another known RL value of BM.

In between the BMs, a number of change points (CPs) will be set up to observe the fore sight reading and the back sight reading of each stationed staves and the values are booked. Upon completion of the observation, the RL values will be calculated and booked. After the RL values are known, three (3) arithmetical checks will be calculated to ensure the precision of the works. Consequently, the adjustment value can be computed where this value will be distributed accordingly to each station. Finally, the adjusted RL values are booked and the misclosure will be calculated to be compared with the adjusted values to determine whether the levelling works is accepted or unsatisfactory.

2.0 )

Objective & Instruments Used

Objective in this report for :

1. Able to carry out fly level observation observation (Rise and Fall method) from BM/ standard standard bench mark (SBM) to temporary bench mark (TBM). (TBM). 2. Able to compute the transferred RL from BM/SBM to TBM. 3. Able to adjust and check the levelling data.

Instrument used :

1. 1 x Level 2. 2 x Staff 3. 3 x Tripod

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3.0 )

Methodology and Data Processing: Processing:

1. The level is set up at a convenient position, I 1. The staff is held on the BM and a reading is taken. This will be a back sight (BS), because it is the first staff reading after the levelling instrument has been set up. The length of foresight and back sight should be as equal. 2. The staff is moved to point A and take reading. This will be a foresight (FS). And point A will be a change point (CP). 3. Next, the levelling instrument instrument is moved to position position I2 and the staff is left at point A and point B on the change point (CP). The staff is turned so that it faces the level and a r eading is taken. This will be a back sight for for point A and and fore sight sight for point B. B. 4. Next, the levelling levelling instrument instrument is moved to position I3 and the staff is left at point B and point C on the change point (CP). The staff is turned so that it faces the level and a r eading is taken. This will be a back sight for for point B and fore sight sight for point C. C. 5. The same step is repeated for the position I 4. The level instrument is set up and the reading for both staff at point point C and D are taken. taken. 6. While the staff remains at D, the instrument level is moved to another position, I 5. A reading taken from new position to the staff at D. This is a BS.

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7. The staff is moved to TBM and E in turn and reading taken while the level at I 5. Point E will be the FS and TBM will be an intermediate sight (IS) . 8. Move the level at position I 6 and move the staff at point E and point F then take both readings. The BS is point E and FS is point F. 9. The same step for position I 7, move the staff at point F and point G and take the readings. 10. Finally, the level is moved to I 8, a BS is point G and FS is the BM. The final staff position is at a point of known RL. This is most important as all levelling levelling fieldwork must start and finish at points of known reduced reduced level, level, otherwise otherwise it is not not possible to detect detect misclosures misclosures in the the levelling. levelling.

4.0 Result & Analysis

The reading are shown booked by the rise and fall method in table 1.1. These are normally recorded in a level book containing all the relevant column. Each line of the level book corresponds to a staff position and this is confirmed by the entries entries in the Remarks Remarks column. column. The calculation calculation proceeds proceeds in the following manner, in which the reduced level of a points is related to that of a previous point. Back sight (BS), m 2.225 2.006 2.234 2.548 1.258

Intermediate Sight (IS), m

Fore sight (FS), m

0.823 0.790 0.910 1.259 1.024

0.843 0.292 0.509

11.915 - 11.915 00.00

Rise, m

1.402 1.216 1.324 1.289 0.234

1.631 1.928 2.384 2.190

11.915

Fall, m

0.607 1.085 2.092 1.681

5.465 + (-5.465)

5.465

0.00

Adjusted RL, m

Remarks

44.565 45.967 47.183 48.507 49.796 50.030 49.423 48.338 46.246 44.565

BM 44.565 A B C D TBM 50.030 E F G BM 44.565

44.565 - 44.565 0.00

Table 1.1 Rise and Fall Method

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Allowable Misclosure = ± 5√  mm =14.142mm =0.014 m


1) From the first BM to A there is a rise. A BS of 2.225 m has been recorded at the BM and FS of 0.823 m at A. The resulting height difference is given by (2.225m – 0.823m) = +1.402 m. The positive sign indicates indicates the rise and is is entered at point A. 2) The procedure is repeated and the height difference from A to B is given by (2.006m -0.790m) = + 1.216 m. This is entered at point B. 3) When calculating the rises or falls in the FS or IS column must be subtracted from the line immediately above, either in the same column or one column to the left. The FS is subtracted from the IS or BS in the line above and the BS on the same line as the FS is the used to continue the calculation with the next IS or FS in the line below. 4) When the table is complete, a check on the arithmetic involved is possible and must always be applied. This check is

∑ (BS ) - ∑ ( FS ) = ∑ ( RISES ) - ∑ ( FALLS ) = LAST RL – FIRST FIRST RL

5) In table 1.1, the difference between the adjusted RL of the first BM and adjusted RL of the final BM is 0.00. The result show that the levelling is accurate and pricise. It is mean that we do not have to make an adjustment.

6) The allowable misclosure for any levelling sequence is allowable misclosure = misclosure = ±5√  mm where n is the number of instrument positions. If the actual value is greater than the allowable value, the levelling should be repeated. However, if the actual value is less than the allowable value, the misclosure should be distributed equally between the instrument positions.

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5.0 Conclusion

We manage to carry out fly level observation from Bench Mark (BM) to Temporary Bench Mark (TBM). All the readings data were booked by the rise and fall method. Arithmetical check was applied in fly level method for verify the accuracy of calculation.

ƩBS – ƩFS = Ʃ rises – Ʃ falls

=

last RL – 1 1 st RL is the arithmetical check to verified the accuracy of calculation. calculation. The arithmetical

check found that all the value were equal to 0.00m, meant that the accuracy of calculation were verified.

The leveling was done from a known BM to unknown TBM and reversed to the known BM again. Then we compute the transferred level from BM to TBM and compute the level back to the BM to checked our data is correct. The compute reduced level on the TBM is 50.030m and the reading from TBM back to the BM is equal to the known level of the BM , 44.565m. The allowable misclosure is used to check the precision of leveling data, ± 5√n mm where n is th e number of instrument positions. The allowable misclosure is found to be ± 14mm in our practical which is we have eight of instrument positions. The actual value is less than the allowable value, which is that actual value is 0.00m and the allowable misclosure is ±0.014m . It proved that our work is accepted.

6.0 Comments

6.1 Upon completion of the transferred of height using the levelling technique practical, we have learned five new things which are:

a) Measuring height using staff b) Setting up, operate and balancing the staff with the circular bubble c) Learning how the levelling is conducted d) Calculating the reduced levels e) Learning the precision of levelling

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6.2 Levelling is a task that requires teamwork and accuracy to be carried out fly level observation from Bench Mark (BM) to Temporary Bench Mark (TBM) efficiently. By the end of the practical, practical, we have met the objectives objectives in this this practical which which are transferred transferred of reduced reduced level from BM to TBM and calculation of reduced level. Firstly, in carrying out this fieldwork, we assigned all the procedure required according group set up the tripod, ensure the top is level, push legs firmly into the ground, use foot screw to centralize the circular bubble, test to see if the compensator is working and remove the parallax.

After that, we conduct the test by assigning different individuals holding the staff. We also let everyone read the levelling instrument so that everyone can learn how to read values on the staff and record the data. In calculating the reduced level of levelling instrument, we gathered all the data and booked the reading by the rise and fall method.

6.3 In this practical, we managed to fulfill all the requirements and specifications of this practical tasks such as reading the staff from the instrument position. All our practical of fly level observation, we read back sight , intermediate sight and fore sight.

6.4 A problem we encountered during the practical was reading and booking errors. Many mistakes can be made during the booking of staff readings taken with an tilting level, and the general rule is that staff readings must be carefully entered into the levelling table or field book immediately after reading. We have done this practical twice, which is our first practical result was rejected. This is because the actual value is greater than allowable value.

The next problem we faced was balancing the staff. When the reading is being taken, the staff

is unbalanced due to the uneven ground surface and hot weather disrupted the holder’s concentration. Alas, we gave gave timed signals so that the staff holder can concentrate for a few seconds while the reading is being taken.

The next problem is weather conditions .In strong winds, a level can become unstable because the line of sight is always moving and it is also difficult to hold the staff steadily. For

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these reasons, it is not possible to take reliable readings under these conditions which should be avoided when levelling. Therefore we had to find the suitable time to carry out our fieldwork.

6.5 We tr uly uly

appreciate each other’s commitment and attention when conducting the levelling

practical to achieve the objective efficiently. efficiently. Even we have to stopped half way of our practical because of of the rainy day , but our members do not give up to continue continue the practical on other other day. Not only that we need to redo our practical because the first practical result is not acceptable. At last, we manage to complete our second practical smoothly.

6.6 Faiz Arif

: Commitment: 10/10 Leadership: 10/10 Attendances: 10/10

Mohd Norizuan


Nurfatin Aida Aida

: Commitment: Commitment: 10/10 Leadership: 10/10 Attendances: 10/10

Farah Nurain


Assyiffa


Rabiatul Adawiyah


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7.0) 1.

References

SURVEYING FOR ENGINEERS : J.UREN AND W.F.PRICE : THIRD EDITION : ISBN 0-333-57705-1 .

2. 2) LECTURE NOTE, PROF SR. DR. HJ. ABD MANAN BIN HJ.SAMAD, ENGINEERING

SURVEYING 1.

8.0)

Appendix

Diary of work : We were given a task to do in a group, this task must complete in duration two weeks, this task about transfer of height using the levelling techcnique. The first week on 13 october, 2014 we were not able to do this practical because the first week we still using for finish the second task (two peg test). We started our field work for transfer of height using the levelling technique is on 20 October, 2014 Monday and 24 October, 2014 Friday in the evening, on this date was to spare us. Firstly before starting the work we need preparation of equipment first. We go to G-store science surveying geomatic for get instrument such level, staff and tripod. We bring tools go to the work area near the pusat islam there are bench mark (BM) and temporary bench mark (TBM). Before start reading we must know where the point for start, first conduct fly level from BM to TBM and assume the distance from BM to TBM. After that set up the instrument levelling at the point A and staff at the point BM get the reading back side side (BS) and get get the reading fore side(FS) next change the levelling at the point B(change point) and staff stay at the same point then get the reading back side(BS) and get the reading fore side(FS). do it until at the final point at the TBM, next repeat reading another point and get the reading from TBM to BM also. We finally finish our work on that field day. All the data we recorded.

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Supporting information :

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REPORT LEVELLING

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