Ss report 1

! SCHOOL OF ARCHITECTURE, BUILDING & DESIGN!!

BACHELOR OF QUANTITY SURVEYING (HONOURS)

QSB 60103 - SITE SURVEYING

Fieldwork Report 1

Levelling !!!!

NAME STUDENT ID NO. MARKS

NG WAI KHONG 0317980

PAN LEK VUN! 0323164

PANG KHAI SHUEN 0318423

SHERLYN ANG TSE YUN 0317977

!!Table of Contents !

!Contents

!Page No.

!Cover Page

! 1

!Table of Contents

! 2

!Introduction to Levelling

!3 - 4

!Apparatus Used

!5 - 7

!Field Data

!8 - 9

!Adjusted Field Data

! 10 - 11

!Discussion

! 12

2

What is Levelling? Levelling is the measurement of geodetic height using an optical levelling instrument and a level staff or rod having a numbered scale. Common levelling instruments include the spirit level, the dumpy level, the digital level, and the laser level. (Wikipedia, 2015) In our assignment, we are using Spirit (optical) Levelling.

!What is a Level Surface?

A Level Surface as a surface that is plumb; It is at right angles with the centre of the Earth at all sides. An instrument has to be set-up at a Levelled surface to get an accurate reading. This can be achieved by using a spirit level.

!What is Datum?

A datum is an abstract coordinate system with a reference surface that provides known locations to begin surveys. (National Oceanic And Atmospheric Administration, 2014)

!There are two types of datum: Ordnance Datum and Assumed Datum

a) Ordnance Datum is a vertical datum which provides a basis for surveying and is referred to by all heights shown on Ordnance Survey maps. Usually Mean Sea Level is used for the datum.

b) Assumed datum is a datum transferred to a location near to the surveyed site when the Ordnance datum is inconvenient or impossible to relate to.

What are Bench-marks?

!!A bench-mark is a post of other permanent mark established at a known elevation that is used as the basis for measuring the elevation of other topographical points. This is a bench-mark found at Jelutong Post Office. (Geocaching.com – Groundspeak Forum)

!!!Temporary bench-marks can be set-up by a surveyor for his own works. It should be a stable, semi-permanent mark.

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3

!Reduced Level

A reduced level is the height of a point in relation to the datum. It is calculated from a known datum that is usually chosen as the starting point.

!Back-sight

This is the first reading taken after the auto-level is set up. The point taken by this is should have a known height, or which height can be calculated.

!Foresight

This is the last reading taken before the auto-level is moved to another point.

!Intermediate sight

This is any readings taken between Back-sight and Foresight. It is sometimes called inter-sight.

!Change Point (Turning Point)

It is an arbitrary point at which the auto-level is moved to another position.

!Line of Collimation

A horizontal line of sight joining the intersection of crosshairs of the optical centre of the object glass.

4

Apparatus Used  Auto Level  A dumpy level, builder's auto level, leveling instrument, or automatic level is an optical instrument used to establish or check points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and to transfer, measure and set heights. It includes an internal compensator mechanism (a swinging prism) that, when set close to level, automatically removes any remaining variation from level. This reduces the need to set the instrument truly level, as with a dumpy or tilting level. Self-levelling instruments are the preferred instrument on building sites, construction and surveying due to ease of use and rapid setup time.

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5

An automatic level uses a swinging prism to compensate for small inclination deviations.

Auto Level Tripod  A three-legged tripod ia a device used to support any one of a number of surveying intruments, such as theodolite, total stations, levels or transits.

!!Levelling Rod   A levelling rod, also called a level staff is a graduated wooden or aluminium rod, used with auto level to determine the difference in height between points or heights of points above a datum surface.  

!

!6

Two sides of a modern surveyor's levelling rod. Metric graduations are on the left, imperial on the right.

!Horizontal bubble level  

!A horizontal bubble level is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). To check the accuracy of a level, a perfectly horizontal surface is not needed. The level is placed on a flat and roughly level surface and the reading on the bubble tube is noted. This reading indicates to what extent the surface is parallel to the horizontal plane.

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7

!!Field Data !Rise and Fall Method  !

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BS IS FS Rise Fall Reduced  Level

1.805 100.000

1.548 4.065 2.26 97.740

1.575 1.515 0.033 97.773

1.485 1.670 0.095 97.678

1.830 1.545 0.06 97.618

1.553 1.589 0.241 97.859

1.593 1.830 0.277 97.852

1.662 1.530 0.063 97.645

3.698 1.500 0.162 97.807

1.818 1.505 2.193 100.00

1.833 0.015 99.985

18.567 18.582 2.692 2.707 99.985

-­‐18.582 -­‐2.707 -­‐100.000

-­‐0.015 -­‐0.015 -­‐0.015

8

!Height of Collimation

!!Acceptable Misclosure = 12+/- √k ;

K = the number of set-ups ;

12+/-√11 = +/- 39.799mm ;

The levelling is acceptable.

BS IS FS Height  of  Collima9on Reduced  Level

1.805 101.85 100.00

1.548 4.065 99.288 97.740

1.575 1.515 99.348 97.773

1.485 1.670 99.163 97.678

1.830 1.545 99.448 97.618

1.553 1.589 99.412 97.859

1.593 1.830 99.175 97.582

1.662 1.530 99.307 97.645

3.698 1.500 101.505 97.807

1.818 1.505 101.810 100.00

1.833 99.985

18.567 18.582 99.985

-­‐18.582 -­‐100.00

-­‐0.015 -­‐0.015

9

!Adjusted Field Data  !Rise and Fall Method  

!

!!!

BS IS FS Rise Fall Reduced  Level Adjustment

Final  Reduced  Level

1.805 100.00 100.000

1.548 4.065 2.26 97.740 +0.0015 97.742

1.575 1.515 0.033 97.773 +0.0030 97.776

1.485 1.670 0.095 97.678 +0.0045 97.683

1.830 1.545 0.06 97.618 +0.0060 97.624

1.553 1.589 0.241 97.859 +0.0075 97.867

1.593 1.830 0.277 97.582 +0.0090 97.591

1.662 1.530 0.063 97.645 +0.0105 97.656

3.698 1.500 0.162 97.807 +0.0120 97.819

1.818 1.505 2.193 100.00 +0.0135 100.014

1.833 0.015 99.985 +0.0150 100.00

18.567 18.582 2.692 2.707 99.985

-­‐18.582 -­‐2.707 -­‐100.000

-­‐0.015 -­‐0.015 -­‐0.015 Arith.  Checked

10

!Height of Collimation  

!

!!!!

BS IS FS Height  of  Collima9on

Reduced  Level Adjustment

Final  Reduced  Level

1.805 101.85 100.00 100.000

1.548 4.065 99.288 97.740 +0.0015 97.742

1.575 1.515 99.348 97.773 +0.0030 97.776

1.485 1.670 99.163 97.678 +0.0045 97.683

1.830 1.545 99.448 97.618 +0.0060 97.624

1.553 1.589 99.412 97.859 +0.0075 97.867

1.593 1.830 99.175 97.582 +0.0090 97.591

1.662 1.530 99.307 97.645 +0.0105 97.656

3.698 1.500 101.505 97.807 +0.0120 97.819

1.818 1.505 101.810 100.00 +0.0135 100.014

1.833 99.985 +0.0150 100.00

18.567 18.582 99.985

-­‐18.582 -­‐100.00

-­‐0.015 -­‐0.015 Arith.  Checked

11

!Discussion   In this field work we were required to measure the reduced level of 10 locations around the Staff Parking at Taylor’s University Lakeside Campus. We started out by assuming a R.L of 100.000m AOD at a lamp post labelled BM 101. Aside from this assumed R.L, we need to calculate the R.L. or 10 other locations, which means we need to do 10 separate set-ups of the auto level.

!One of the difficulties we faced was making sure the bubble is in the middle of the spirit level. As there were only two points to read once the instrument was set, we did not have Intersight readings, but only Backsight and Foresight.

!Once the readings were taken, we used two methods to calculate the reduced level, namely the Rise and Fall Method and Height of Collimation Method. We arrived at a misclosure of -0.015m, which was in the acceptable error range. We then distributed the error to arrive at our final reduced level readings.

!Overall, this is a very new experience for us handling surveying instruments, and we really enjoyed the process of doing this fieldwork.

!!

12