SCHOOL OF ARCHITECTURE, BUILDING AND DESIGN

BACHELOR OF SCIENCE ( QUANTITY SURVEYOR )

QSB 60103 SITE SURVEYING

Fieldwork 1 Report : Levelling

Group member :

Lim Chern Yie 0315688

Leong Chee Mun 0316256

Muhammad Hasif bin Alias 0316413

Liew Yong Sheng 0315108

Table of Content

Introduction 2

Apparatus of Fieldwork 5

Objective 7

Field Data 8

Summary 12

Reference 13

Introduction

Levelling is the determination of the relative heights (altitudes) of the different points in the area under survey, it is this information which, when coupled with that of the pan, enables a section through the land and/or artifacts to be drawn.

The primary reference at levelling recording stations is a set of stable bench-marks, installed in locations where their level should not change. Upon initial set-up of a station, the levels of the relevant parts of the installation are established and recorded by means of accurate levelling.

Levelling and surveying methods are also used for measurements of river channel and lake configurations. Often, less accurate methods can be used for this work than for water-level recording stations, although the techniques are common.

Backsight (B.S.) - The first reading from a new instrument position.

Intermediate Sight (I.S.) – Readings between the backsight (B.S.) and foresight (F.S.)

Foresight (F.S.) - The last reading from an instrument position.

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

Reduce Level (RL) - The vertical distance between a survey point and the adopted level datum.

Bench mark (BM) - The term given to a definite, permanent accessible point of known height above a datum to which the height of other points can be referred.

As most levels will have some level of collimation blunder, a strategy is obliged to check if the mistake is inside worthy breaking points. This is known as a two-peg test. This should be led when utilizing another or distinctive level interestingly and at standard interims from that point.

Stage 1

On fairly level ground, two points A and B are marked a distance of Lm apart. In soft ground, two pegs are used, on hard surfaces nails or paint may be used.

The level is set up midway between the points at C and carefully levelled. A levelling staff is placed at A and B and staff readings S1 (at B) and S2 (at A) are taken.

The two readings are: S1=(S1‘+x)andS2=(S2‘+x)

Since AC = CB, the error x in the readings S1 and S2 will be the same. The difference between readings S1 and S2 gives:

S1 -S2 =(S1‘+x)–(S2‘+x)=S1‘-S2‘

This gives the genuine contrast in tallness in the middle of A and B. This shows that if a collimation slip is available in a level, the impact of this offsets when tallness contrasts are registered given readings are assumed control equivalent locating separations.

Stage 2

The level is then moved so that it is L/10m from point B at D and readings S3 and S4 are taken.

The difference between readings S3 and S4 gives the apparent difference in height between A and B. If the level is in perfect adjustment then: S1 – S2 = S3 – S4

On the off chance that the consequences of these tests demonstrate that the collimation mistake is under 1mm for each 20m (or some predetermined quality). In the event that the collimation lapse is more prominent than this predefined esteem then the level must be balanced. This is typically done by the maker or a prepared expert.

Apparatus of Fieldwork

1) Automatic Level

2) Tripod

A tripod is a portable three-legged frame, used as a platform for supporting the weight and maintaining the stability of some other object. A tripod provides stability against downward forces, horizontal forces and moments about the vertical axis.

An Auto-Level is a Professional Leveling Tool used by Contractors, Builders, Land Surveying Professionals, or the Engineer who demands accurate leveling every time. AutoLevels set up fast, are easy to use, and save time and money on every job. Auto-Levels require that you level the instrument by hand, but you're only required to get the bubble within the black circle on the bubble vial, from the Auto-Levels compensator takes over and precisely levels itself.

3) Optical Plummet

4) Level Rod

A device on some transits and theodolites; used to center the instrument over a point, in place of a plumb bob, which moves in a strong wind. It also can make sure that the apparatus like automatic level is in the horizontal level.

A graduated rod used in measuring the vertical distance between a point on the ground and the line of sight of a surveyor's level.

Objective

- To recognize conceivable errors.

- To determine the error of misclosure in order to determine whether the levelling is acceptable or not.

- To establish a new benchmark.

- To produce a significant over leveling method.

Field Data

Rise and Fall Method

BS IS FS RISE FALL RL Remarks

1.500 100.000 BM1

1.385 3.815 2.315 97.685 TP A

1.470 1.350 0.035 97.720 TP B

1.470 1.560 0.090 97.630 TP C

1.600 1.540 0.070 97.560 TP D

1.390 1.315 0.285 97.845 TP E

1.320 1.360 0.030 97.875 TP F

1.390 1.555 0.235 97.640 TP G

1.355 1.305 0.085 97.725 TP H

2.795 1.385 0.030 97.695 TP I

1.375 0.445 2.350 100.045 TP J

1.455 0.080 99.965 BM1

Arithmetical Check :

∑Rise - ∑Fall = Last Reduced Level Reading - First Reduced Level Reading

17.05 - 17.085 = 2.785 - 2.820 = 99.965 - 100.000 = - 0.035

Acceptable Misclosure = 12+/- √K

K = the number of set-ups

12+/- = +/- 39.799 ∴ The levelling is acceptable

Height of Collimation Method

BS IS FS HC RL Remarks

1.500 101.50 100.000 BM1

1.385 3.815 99.07 97.685 TP A

1.470 1.350 99.19 97.720 TP B

1.470 1.560 99.10 97.630 TP C

1.600 1.540 99.16 97.560 TP D

1.390 1.315 99.235 97.845 TP E

1.320 1.360 99.195 97.875 TP F

1.390 1.555 99.03 97.640 TP G

1.355 1.305 99.08 97.725 TP H

2.795 1.385 100.49 97.695 TP I

1.375 0.445 101.42 100.045 TP J

1.455 99.965 BM1

Arithmetical Check :

∑BS - ∑FS = Last Reduced Level Reading - First Reduced Level Reading

17.05 - 17.085 = 99.965 - 100.000 = - 0.035

Acceptable Misclosure = 12+/- √K

K = the number of set-ups

12+/- = +/-39.799mm ∴ The levelling is acceptable

Adjusted Data

Rise and Fall Method

BS IS FS HC RL Adj. Final RL Remarks

1.500 101.50 100.000 100.000 BM1

1.385 3.815 99.07 97.685 +0.00318 97.688 TP A

1.470 1.350 99.19 97.720 +0.00636 97.726 TP B

1.470 1.560 99.10 97.630 +0.00954 97.640 TP C

1.600 1.540 99.16 97.560 +0.01272 97.573 TP D

1.390 1.315 99.235 97.845 +0.01590 97.861 TP E

1.320 1.360 99.195 97.875 +0.01908 97.894 TP F

1.390 1.555 99.03 97.640 +0.02226 97.663 TP G

1.355 1.305 99.08 97.725 +0.02544 97.750 TP H

2.795 1.385 100.49 97.695 +0.02862 97.724 TP I

1.375 0.445 101.42 100.045 +0.03180 100.077 TP J

1.455 99.965 +0.03498 100.000 BM1

Correction per set-up

= Error of misclosure ÷ Number of set up

= ( 100.0000 - 99.965 ) ÷ 11

= + 0.00318

Height of Collimation Method

BS IS FS HC RL Adj. Final RL Remarks

1.5 101.5 100.000 100.000 BM1

1.385 3.815 99.07 97.685 +0.00318 97.688 TP A

1.47 1.35 99.19 97.720 +0.00636 97.726 TP B

1.47 1.56 99.1 97.630 +0.00954 97.640 TP C

1.6 1.54 99.16 97.560 +0.01272 97.573 TP D

1.39 1.315 99.235 97.845 +0.01590 97.861 TP E

1.32 1.36 99.195 97.875 +0.01908 97.894 TP F

1.39 1.555 99.03 97.640 +0.02226 97.663 TP G

1.355 1.305 99.08 97.725 +0.02544 97.750 TP H

2.795 1.385 100.49 97.695 +0.02862 97.724 TP I

1.375 0.445 101.42 100.045 +0.03180 100.077 TP J

1.455 99.965 +0.03498 100.000 BM1

Correction per set-up

= Error of misclosure ÷ Number of set up

= ( 100.0000 - 99.965 ) ÷ 11

= + 0.00318

Summary

In this fieldwork, the method used is quite simple, where the reduced level of Bench Mark (BM) 1

is given as 100.00m. The process begins with obtaining the backsight (BS) of BM1 and the foresight (FS)

of turning point (TP) A. Then the auto level is shifted to obtain the BS of TP A and the FS of TP B. This

process is repeated by shifting the auto level to obtain the BS and FS of the following staff stations and

lastly go back to BM1 to obtain its FS in order to calculate the error of misclosure.

Both method of calculation are used which are rise and fall method and the height of collimation

method. They are used to calculate the reduced level of each staff station. The error of misclosure was +

0.00318mm and the acceptable range of error of misclosure was calculated using the 12+/- √k formulae

where k represents the number of set-ups, and the acceptable range of error of misclosure is +/-

39.799mm. Thus, the leveling is acceptable.

To distribute the error, the correction per set-up is calculated using the following formulae:

Correction per set-up = Error of misclosure ÷ Number of set up

The correction per-set up is +0.00318mm and is cumulative as shown in the table provided in the

adjusted data section.

Reference

1. Brinker, R. (1995). The surveying handbook (2nd ed.). New York: Chapman & Hall.