VERTICAL DISTANCE MEASUREMENT BY RISE AND FALL METHOD

Date : 13 March 2012

Time : 11.00 am – 2.00 pm

Place : Around Tasik Kejuruteraan, UKM

Title : Surveying Practical

Introduction

Levelling is the operation required in the determination or the comparison of heights of points on the surface of the earth. Levelling also is the procedure used when one is determining differences in elevation between points that are remote from each other .An elevation is a vertical distance above or below a reference datum. In land surveying , the reference datum is mean sea level (MSL) .

Taping refers to the exercise of physically measuring horizontal distances. The equipment required in taping are, 30 meter tape, tension handle, tape grips ,plumb bobs and chaining pins .

Objective

1) to find out how surveying telescope / dumpy level works.

2) To find out the field procedures that are used for determining heights when leveling

3) To study land profile of Tasik Kejuruteraan, UKM.

Method

For this field work, we used the rise and fall method.

Equipment

Engineering level/ dumpy level consist of adjustable telescope

30 metre tape use to measure the distance of two staff.

Levelling staff to measure vertical distances

Tripod The support dumpy level.

Bubble to make sure the levelling staff straight vertically

Log book collect all the data

Area of Survey

We choose the street’s light as the temporary bench mark to make it easier because we didn’t given specific bench mark. The survey are made it in circular direction so we can more easily study the profile of the Tasik. Since this is only practical of engineering level/dumpy level so we’re not the specified with horizontal distance and specified with vertical distance.

The picture below show the region of survey.

Data Analysis

BS FS RISE FALL RL ADJUST ADJ RL MARK1.375 100

1.360 0.015 100.015 -0.2065 99.8085 A1.23

3.072 1.842 98.173 -0.413 97.76 B0.557

1.330 0.773 97.400 -0.6195 96.7805 C4.850

1.424 3.426 100.826 -0.826 100 100

Checking:

∑ Backsight=8 .012∑ Foresight=7 .186

0.826

∑ Rise=3. 441∑ Fall=2.615

0.826

∑ LastRL=100 .826∑ InitialRL=100 .00

0.826

Discussion

In surveying, three basic quantities are measured – heights, angles, and distances - leveling is the name given to one of the methods available for determining heights.

The equipment required to carry out leveling is an surveying telescope/dumpy which is normally mounted on a tripod and used in conjunction with a leveling staff.

Leveling is used to find out the difference in level between points A and B. In leveling and for most field work, we have to have a starting point, which the heights is known and this point is called TBM which stands for Temporary Bench Mark. We were supposed to do close leveling, which indicates that our first and last point’s heights are same, which is 100m (approximate) .

Procedure of Levelling.

1) Set off the temporary bench mark. We chose the street’s light to be our temporary bench mark with the mean sea level of 100m.

2) Set up the equipment. i) The tripod was set up in the halfway of points that we were about to measure.

ii) We were supposed to set up the tripod until the bubble is located at the center of the circle on the adjustable telescope.

iii) When the tripod and the dumpy is levelled properly, this would help us to have a perfectly line of sight where we can rotate it around the horizon whithout messing out the bubble.

3) Lining in i) We were supposed to set up a parameter of more than 60 metres.ii) For this field work, we were supposed to do a close levelling. iii) Since the measurement tape’s length is only for 30 metres, we have to break

down the distance into few points. iv) The few points are the reference point that were marked so that we’ll know our

boundary.

4) Back sight (BS) and fore sight (FS). i) After we measured, marked the points and set up our dumpy level, the levelling

staff was placed in a way that we can measure our back sight and fore sight.ii) Make sure the levelling staff is levelled correctly using the bubble staff. iii) The dumpy level is focused on the staff.iv) The reading was taken from the cross hair of the dumpy level.

5) Placing the instrument i) First off, we start at A (TBM), the first measurement is a back sight to A, and the

second is fore sight to B.ii) Then, the dumpy level was moved in front of B, where the staff at B remain

still( Back sight) , the other staff is placed in front of the dumpy level as the foresight

iii) Next, the staff (just now fore sight, now back sight ) stand still, while the dumpy moved in front of it ( point C) , and the other staff is moved in front of the dumpy (fore sight)

iv) The steps are repeated until, the end point, where the dumpy is placed between Z(back sight) and A( fore sight ) .

6) Recording the distance The total length must be reported and recorded correctly.

7) After the levelling, we were supposed to do a data analysis, where to check whether we get the correct value of our closed levelling. If we get the value which is higher or lower then what we were supposed to have which is 100m, we have to calculate the misclosure, to make sure that our value does not exceed the allowable misclosure. And

if the summed of heights is not comparable with the temporary bench mark, and it exceed the allowable misclosure, the entire levelling must be repeated.

Misclosure

If misclosure > allowable misclosure , the survey must be taken again.

Allowable misclosure =±m√nm = constant = 5n = number of marking

Error

The theoretical value for the TBM2 is 100m , while the TBM 2 value based on our calculation is 100.826m.since there is difference in the theoretical value, this might happen due to some error.

1) Instrument errors.1.1) Adjustable telescope : Water and dust penetration. 1.2) Leveling staff : Zero error from leveling staff.

The staff was broken. 2) Natural errors.

2.1) Unstable groundThe leveling staff and tripod leg may sink into ground during the leveling process.

3) Collimation error.This occur if the sight lenths from one instrument positions are not equal.So, sight lengths should be kept equal, particularly back sights and fore sights and before using any level it is advisable to carry out a two peg test to ensure the collimation error is within acceptable limits.

3) Personal errors. Errors will arise from carelessness by the survey crew:3.1) leveling staff is not vertical.

The pond bubble was not center. A good procedure is to rock the staff slowly back and forth through vertical whenever possible and to note the lowest reading .

3.2) faulty reading of the tapeParallax error occur when the crew’s eyes is not perpendicular to the cross hair of the staff.

3.3) tripod is not vertical. The tripod also might be disturbed during the leveling.Do not disturb the tripod as in kick, touch and etc. while carry out leveling,

How to reduce the chance of errors occurring.

When leveling, the following procedures should be used if many of the sources of error are to be avoided.

Leveling should always start and finish at temporary bench mark, so that misclosure can be detected.

Where possible, all sight lengths should be below 50 meters to enable the staff to be read accurately.

The staff must be held vertically by suitable use of a circular bubble or hold by hand.

Conclusion

From the objectives given:

1. Our group can handle the surveying telescope/dumping level properly and precisely like what have been told in the lecture and also from the practical.

2. We found out the procedure of field to do leveling.3. We learn how profile of land at Tasik Kejuruteraan UKM.

DEPARTMENT : CIVIL ENGINEERING (STRUCURAL AND ENVIRONMENTAL)

COURSE TITLE : SURVEYING ENGINEERING

ASSIGNMENT : SURVEY PRACTICAL ( ENGINEERING LEVEL/DUMPY LEVEL)

GROUP MEMBER:

NAME MATRIC NO.

FAIZAH BINTI OMAR A136019

AHMAD NAFEK BIN AUGUST FOUZY A137389

NURASYIKIN BINTI IBRAHIM A137754

CHUAH RUN EN A138030

NORAFIFAH BINTI JOHAR ARIFFIN A138205

NUR FARHANA NADIRA BINTI SAZALI A137818

CHONG CHUN WEN A137672

LECTURER : DR. SHARIZAN BAHAROM

DATE : 13 MARCH 2012