UNIVERSITI TUN HUSSEIN ONN MALAYSIA REPORT OF SURVEY CAMP: TWO PEG TEST AND LEVELLING GROUP 1 LECTURER: ENCIK ANUAR MOHD SALEH GROUP MEMBER ABDUL AZIZ AL-JABBAR BIN MOHD NASIR AHMAD SOFYAN FATIMI BIN MOHAMED ROSLI AATIYAH SHATIRAH BINTI AHMAD SHAKRI AIN AMIRA BINTI MARHALIM AINUL KAMALIAH BINTI SHARIFF
TWO PEG TEST 1.0
Introduction Two peg tests is a surveying operation carried out to determine whether the levelling bubble and telescope line of sight are parallel.
2.0
Aim Peg test is a surveying operation carried out to determine if the levelling bubble (bubble axis) and telescope line-of-sight (line of collimation) are parallel.
3.0
Equipments 3.1 level and tripod (1 set) 3.2 staff (2 sets) 3.3 staff bubble (2 sets) 3.4 tape (1 set)
4.0
Procedures 4.1 Each group will be required to perform a peg test to check the
5.0
4.2
instrument. Each person in the group should record the result of the peg
4.3
test in their own field book. Set out and mark on the ground (with wooden pegs driven into
4.4 4.5
the earth, or roofing nails in tar) two point some 30 m part. Set up instrument midway between two pegs. Read staff on each peg (back sight and foresight), and
4.6
calculate height difference. Next, move instrument about L/10=3m beyond one of the
4.7
pegs (normally fore staff position). Read staff on each peg again, and calculate height difference
Observations Data and Analysis 60 m
Reading staff B( ) First set up
Reading staff A
=m
( ) 1.540
Reading staff B(
First set up
1.240
Reading staff A(
) 1.325
0.300
Height difference = m’
) 1.085
Difference (m-m’)
30 m -
5.1 5.2
Height difference
0.240
60 m 0.060
If m=m’ then the instrument is OK! I f NOT then the error is : / L mm/m
5.3
6.0
The error is called collimation error. Acceptable error : 1mm per 20 m.
Discussion There were some error occur during this two peg test. The first one is when the position of the leveling instruments was changed
from its original position, it will affect the height of the leveling instruments because there will be changes to the tripod stand length. Moreover, the reading of the staff is different every time the reading were taken, this happen due to the different height of the tripod stand when the setting up process. Furthermore, an error also happens because the staff didn’t remain still and this affect the distance between the staff and the leveling instruments. During this peg test, two peg tests were tested at the same places along 60m in a straight line. Basically, there should be no error if the leveling bubble and the telescope-line-of-sight are parallel but the error that occur are different for each distance and it is bigger than the allowable error. The allowable error for this peg test is 1mm per 20m and for 120m the acceptable error is 7mm or 0.007m. If more than that, it is advised to do instrument calibration.
7.0
Conclusion The allowable different that is accepted due to the set up is 7mm. Hence our difference is 0.060m or 60mm, the instrument was not in a good condition.
LEVELLING 1.0
Introduction Vertical Control is the general term applied to any of the various processes by each elevation of points or differences in elevation are determined. It is the vital operation in producing necessary data for mapping, engineering design, and construction.
2.0
Aim To fly reduces level from known point (Benchmark or Temporary Benchmark) to unknown point.
3.0
Theory of Levelling
Levelling is a process of transferring height above a datum from one point to another point. This levelling process is used in engineering to establish building elevations, layout of highways, determination of flood plains, calculate volumes in earthwork, design and layout of sewage and water lines, develop topographic maps, and student crustal-earth movements.
Benchmark is definite, permanent accessible point of known height above a datum to which the height of other points can be referred.
Calculation in levelling: o
Page check
o
Allowable closure
Allowable closure =
o End closure End closure =
– BM 1
o Adjustment
4.0
Equipments 4.1 level and tripod (1 set) 4.2 staff (2 sets) 4.3 staff bubble (2 sets)
5.0
Field procedures 5.1 observation procedures 5.1.1 Consider a series of measurements of level loop as shown in Figure 3.3 5.1.2 Start at BM A, so the first measurement from Setup 1 is a back sight to BM A, and the first reading is the foresight to CP1 known as a Change 5.1.3
Point. The levelling staffs then remains at CP1, while the instruments moves to Setup 2. Take back sight reading to CP1, and foresight reading to
5.1.4
CP2, and so on. Eventually, at Setup 4, a back sight reading is made to CP3, and
5.1.5
foresight reading to BM A. The traverse is then CLOSED. This allows a check on the levels, since the sum of all the changes in level should be zero.
5.1
5.2
Booking Procedures 5.1.1 The rise and fall method The terms that are commonly used in rise and fall method are: BS= back sight FS= fore sight IS= intermediate sight RL=reduced level Reduction (calculation) Procedures 5.2.1 Checks your survey accuracy, and should be within tolerances given below or suitable for your project. This check should be applied before 5.2.2
you leave the job The following check the arithmetic of your level reductions and must exact :
(BS) - (FS) = RL (last BM) - RL ( start BM) 5.2.3
Disclosure should be : , where K is the length of the traverse in km.
5.2.4
For example, disclosure is +30mm and the length of the loop is 0.7km hence, the disclosure limit is
mm. Therefore, the
disclosure of +30mm is too big (means that the levelling work is not accepted).
6.0
Analysis Data
1. Page check = 16.255 – 16.245 = 0.010 m
= 1.995 – 1.985 = 0.010 m
= 15.530 – 15.520 = 0.010 m
2. End closure End closure = RL (bottom) – BM1 = 15.530 – 15.520 = 0.010m 3. Allowable closure Allowable closure = = = 18 mm 4. Adjustment Adjustment = = 8.33 ×
m
Discussion There were some errors after doing the leveling project. One of the errors happened when getting the wrong reading from the staff. These affect the leveling calculation afterwards. Besides that, distance that is used to do the leveling is not constant due to the
usage of pace instead of measurement tape. As we all know, a human doesn’t have a specific, constant pace so this affect the distance between the staff and the leveling apparatus. Moreover, we also do not know the exact value of a pace in meter. Furthermore, the staffs always moves from its original place because of the traffic in that area, there are lots of vehicle keep on passing through that area. Before we calculate the closure, we need to do the page check first, calculate and see if . Then, if the page check is balanced, we could calculate the closure and if the end closure is less than allowable closure, it means that the closure is accepted and we can calculate the adjustment.
Conclusion For this booking survey, the important thing that we must follow is the distance between the two points must be accurate in order to prevent from getting the parallax, gross and other error that can be occur. The objective of the survey was to determine the Temporary Bench Mark. It should be noted that many of the new technologies provide topographic and environmental data. In order to increase of new technologies, students also must know how to conduct and familiar with the basic and manual operations of this equipment such as tripod and level.
