Cover Page 1

Table of Content 2

Introduction to Levelling 3 – 4

Objective 5

Outline of Apparatus 6 – 7

Levelling Result 8

Adjustment on Misclosure 9

Discussion 10

Conclusion 11

Learning Outcomes 12

Introduction to Levelling


Levelling is the art of determining the relative heights or elevations of a point on the earth’s surface. It deals with measurements in a vertical plane.

In general terms,

Level Surface is any surface parallel to the mean spheroidal surface of the earth. Since the earth is an oblate spheroid, a level surface may be regarded as a curved surface, every point on which is equidistant from the center of the earth.

Vertical Line is a normal line lying on the level surface.

Horizontal Line is any line lying on the horizontal plane. It is usually a straight line tangential to the level line.

Reduced Level is a vertical distance of a point above or below the datum. The elevation of a point is either plus or minus according to the point above or below the datum.

Benchmark (BM) is fixed reference point of known elevation.

Introduction to Levelling


The line of collimation (HI) is the line intersects with the cross hairs of the optical center of the object glass. It is also called the line of sight.

Backsight (BS) is a point whose elevation is to be determined. It is the reading taken after setting up the instrument.

Foresight (FS) is a reading on a point whose elevation is to be determined or on a change points. It is the last reading before shifting the instrument.

An Intermediate sight (IS) is any reading taken on a point of unknown elevation from the same set up of the level. All sights taken between the backsight and the foresight are intermediate sights.

Change Point (CP) is a transfer point of the levelling. It is a point in which the foresight and backsight are taken. Any defined objects can be used as a change point. A benchmark may also be taken as a change point. Sometimes, it is called as a turning point (TP).


Objective

To establish a new benchmark

To determine the difference in height of discrete points

To identify the spot relative heights

To identify possible errors occurred


Outline of Apparatus

Theodolite is a device used widely to determine the horizontal and vertical angles, distance, depths, etc. Besides that, it is used to identify the ground level and the ways to construct super-structure or sub-structure. A basic theodolite consists of a small sized telescope with the mechanism to measure horizontal and vertical angles. Theodolite is able to rotate 360 degree on a tripod stand by a levelling system. The angle can be measured on the scale on the tripod. The calculation of the theodolite is based on the principal of trigonometry, as used in triangulation network. It is a key tool in surveying and engineering work.

Tripod is a rigid type of stand that is capable of fixing minor lateral movement on its top when required. It is used to support the other components of theodolite including the telescope.

Horizontal bubble level is an instrument used to indicate the horizontal level. A slightly curved glass tube which in incompletely filled with either spirit or alcohol.

Optical Plummet is a device that used to center the instrument over a ground station. This component used in place of a plumb bob to center transits and theodolite over a given point.


Outline of Apparatus

Ruler is used to obtain the height of collimation through the scope of theodolite.

Theodolite Telescope is an instrument used to view distant object. Telescope is an arrangement of lens that gather visible light, permitting direct observation of a point through the theodolite in a distance. There is a focusing screw to adjust the clarity of the view in the telescope.


Levelling Result

Backsigh

t

Foresight Rise Fall Line of

Collimation

Reduced

Level

Remarks

1.313 100.000 BM 1

1.415 1.414 0.101 101.313 99.899 TP 1

1.414 1.415 0.000 101.314 99.899 TP 2

1.414 1.313 0.101 101.313 100.000 TP 3

1.112 3.434 2.020 101.414 97.980 TP 4

1.516 1.314 0.202 99.092 97.778 TP 5

1.415 1.516 0.000 99.294 97.778 TP 6

1.515 1.313 0.102 99.193 97.880 TP 7

4.041 1.515 0.000 99.395 97.880 TP 8

1.515 1.414 2.627 101.921 100.507 TP 9

1.213 0.302 102.022 100.809 BM 1

16.670 - 15.861 3.132 - 2.323 Σ

0.809 0.809 0.809 =

Correction = (100.809 – 100.000) / 10

= 0.809 / 10

= 0.081


Adjustment on Misclosure

Calculated

Reduced Level

Line of

Collimation

Remarks Adjustment Adjusted

Reduced Level

Adjusted Line

of Collimation

100.000 BM 1 (0.000) 100.000 100.000

99.899 101.313 TP 1 (0.081) 99.818 101.232

99.899 101.314 TP 2 (0.162) 99.737 101.152

100.000 101.313 TP 3 (0.243) 99.757 101.070

97.980 101.414 TP 4 (0.324) 97.656 101.090

97.778 99.092 TP 5 (0.405) 97.373 98.687

97.778 99.294 TP 6 (0.485) 97.293 98.809

97.880 99.193 TP 7 (0.566) 97.314 98.627

97.880 99.395 TP 8 (0.647) 97.233 98.748

100.507 101.921 TP 9 (0.728) 99.779 101.193

100.809 102.022 BM 1 (0.809) 100.000 101.213


Discussion

Obtained data had been reduced; the copies of results and adjustment are included in this report.

Bench Mark (BM) 1 has been held fixed at a Reduced Level (RL) of 100.00. From there, the backsight (BS) and foresight (FS) are observed and recorded. Then, the amount of rise and fall is gained from the subtraction of BS with FS.

Then, reduced level is being calculated through subtracting or adding the rise and fall, a new reduced level is obtained. This process is then repeated for 9 times from different points at the site. The final reduced level (RL) is to make sure the value is equal or close to the initial RL.

However, in our report, the final RL is slightly more than the initial RL. Thus, there are some errors occurred during the levelling process. If errors occurred, the reduced level must be adjusted using the method we had been taught in class, loop misclosure. Loop misclosure is the anout by which the measured height difference differs from the known height. If the error in a level loop is unacceptable, the leveling must be repeated. However, the error in a level loop in our leveling is acceptable, therefore the error can be distributed according to the distances leveled (or the number of instrument setups). Small misclosure in closed level loops is expected because of the accumulation of errors.


Conclusion

In conclusion, we are able to obtain the data through the usage of levelling equipment provided by lecturer. Even though some errors occurred, we were able to identify it and performed an adjustment to the data we obtained on site. Then, using the obtained data, we were able to conduct a field work report.


Learning Outcomes

Able to conduct a fieldwork report regarding to levelling

Get to experience the equipment on site

Learning the correct ways of levelling

Able to obtain data through the usage of levelling equipment

Able to identify the errors & conduct an adjustment


site surveying report i

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