Contoring

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SURVEYING PRATICAL REPORT

MODULE IIICONTOURING

GROUP I

Bimasena Heribowo ( 1206292351 )

Christopher Kevinly ( 1206223846 )

Wednesson Lawijaya ( 1206230593 )

Date of experiment : 20 – 11 – 2013 Experiment Assistant : Approval date :Score :Assistant Signature :

SURVEYING AND TRANSPORTATION LABORATORYCIVIL ENGINEERING DEPARTMENT

FACULTY OF ENGINEERINGUNIVERSITY OF INDONESIA

DEPOK 2013

Universitas Indonesia

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A. SCOPE

1. Determining the height differences of 25 points to the reference point

(height of instrument).

2. Plotting and arranging the height differences into a countour map with

certain scale.

3. Calculating the distance error index occurred during the observation.

B. APPARATUS

1. A Theodolite

2. A Staff

3. Measuring Tape

4. Pointers

5. Umbrella

6. One Tripod Stand

C. THEORY

Mapping the situation is a combination of polygon creation profile.

Process of measuring a situations measurement requires basic framework

of a horizontal base frame and high-frame basis. The basic framework can

be made horizontally through several ways. Among others: bind to front,

tie back, triangulation, polygon, or a combination some other ways.

While high-Nature are used to measure basic framework. Of the basic

framework can be collected the data - from detailed geometric data

measured. Formulas are given as follows:

∆t = ½ . 100 (a – b) sin 2 θ

d = 100 (a – b) cos2 θ

Where:

∆t: Height differences between theodolite with a point shot

d: horizontal distance between the theodolite with a point shot (optical distance)

a: Upper Cross heirs in meters


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b: bottom cross heir in meters

θ: Oblique angle / Vertical angle

With the formula - the formula above, as well as the formula - basic

formula for determining the coordinates, namely:

XQ = XP + dPQ sin αPQ

YQ = YP + dPQ cos αPQ

Where:

dPQ = Distance from P to Q

αPQ = Azimuth angle from P to Q

D. PROCEDURE

PREPERATION

1. Do the field survey and make a sketch of it

2. Determine the appropriate method to execute the observation efficiently

3. Determine the appropriate reference point where we put theodolite

4. Write down th e point on the sketch up until all the details needed are

available

EXECUTION

1. Place the theodolite on the central reference point and measure the height

of instrument

2. Capture two points that lie along the 0o of horizontal angle and the points

are separated 4 meters from one to each other, then record the cross – lines

of those points.

3. Change the value of the horizontal angle from 0o to 45o, then capture again

two points that are separated by the distance of 5.657 meters from one

point to the other, record the cross – lines.

4. From the outer point of 0o horizontal angle to the outer point of 45o

horizontal angle, measure 4 meters from one point to the other, then mark

it with a pointer and record the cross – lines.


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5. Rotate the theodolite until the horizontal angle changes to be 90o, capture

two points that are separated by 4 meters distance and record the cross

lines.

6. From the outer point of 45o horizontal angle to the outer point of 90o

horizontal angle, measure 4 meters from one point to other, then mark it

with a pointer and record the cross – lines.

7. Repeat step 2 until step 6 by varying the horizontal angle with the value of

45o (135o, 180o, 225o, 270o, 315o, 360o) then capture the points by the help

of a tape and record the cross lines at all points.

E. DATA TABULATION

After the field observation, we get the cross line data at 25 points including the

value of instrumental’s height, at the central point (Y) where we observe those 25

points.

Benchmark = Point M (Theodolite Position)

Theodolite Height (TA) = 141 cm


F G H I J

K L M N O

P Q R S T

U V W X Y

A BZ

C D E

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Data Obtained:

Point BA (cm) BT (cm) BB (cm)

HA

(Angle)

VA

(Angle)

A 70 64.5 58.5 315o 90o

B 13.5 9.1 49 337.5o 90o

C 37 33 29 0o 85o

D 38.5 34 29.5 22.5o 90o

E 162.2 156.5 150 45o 90o

F 93.5 89 84.5 292.5o 90o

G 80.6 78 75.2 315o 90o

H 150 148.0 146.3 0o 85o

I 142.4 139.5 136.6 45o 90o

J 153.4 148.9 144.5 67.5o 90o

K 95.8 93.9 88.9 270o 90o

L 93.0 91.3 89.3 270o 90o

M 0.00 0.00 0.00 0O 90O

N 140.1 138.2 136.3 90O 90o

O 160 157.1 152.1 90o 90o

P 90.3 86 81.5 247.5o 90o

Q 92.3 89.5 86.8 225o 90o

R 137.3 135.3 133.4 180o 90o

S 146.2 143.5 140.4 135o 90o

T 293.9 285 284.2 112.5o 90o

U 83.7 78.0 72.4 225o 90o

V 132.4 128 123.5 202.5o 90o

W 137 133 129 157.5o 90o

X 195 190.6 186.1 157.5o 90o

Y 75.6 69 62.8 135o 102o

F. DATA PROCESSING


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ΔH obtained from the HI (High Theodolite) reduced by BT (Central Cross Heirs).

d is the horizontal distance between the benchmark by which point shot (optical

distance). Formula dtheodolite is 100 (BA-BB) with units of cm. But as BA (Upper

Crossheirs) and BB (Bottom Cross Heirs) is in cm, then it does not need to be

multiplied by 100. So the formula is d = BA-BB. Table processing:

Point ∆H = HI - BT DTheodolite DTape

A 57.5 11.5 11.314

B 110.9 8.6 8.659

C 69.46 8 8

D 86 9 8.659

E 36.5 12.2 11.314

F 31 9 8.659

G 42 5.4 5.657

H 32.13 3.7 4

I 19.5 5.8 5.657

J -28.9 8.9 8.659

K 26.1 6.9 8

L 28.7 3.7 4

M 0 0 0

N -18.2 3.8 4

O -37.1 7.9 8

P 34 8.8 8.659

Q 30.5 5.5 5.657

R -15.3 3.9 4

S -23.5 5.8 5.657

T -165 9.7 8.659

U 42 11.3 11.314

V -8 8.9 8.659

W -17 8 8

X -70.6 8.9 8.659

Y -260.31 12.8 11.314


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G. ANALYSIS

Experiment Analysis

Our aim in this experiment of contour mapping is to collect geometries data from

the earth surface and everything above it. After data is collected, we can draw the

geometries data in a flat plane with selected scale. Above all we need to select an

accurate way that determines basic frame in measuring situation and condition.

Not to mention before the experiment, we need not to forget to prepare instrument

for this experiment.

Experiment is carried in the field near BP3 building. First thing that is done before

carrying this experiment is: drawing a 16x16 meter square then divide it into a

small square of 4 x4 meter. Each point is given coordinates according to its

square. 25 points is used in this experiment while point M is its mid – point and its

benchmark.

Next, we installed theodolite at point M then adjust the water pass in nivo so that

the bubble inside the water pass reach the middle line; this are done by adjusting

the three screw around it. After it had been adjust, next thing we did is we install

pointers in 4th and 8th meters in front, at the sides and backside of the theodolites

and in all of the 25 points.

We start taking down the BA, BT and BB from point C and H with Va 90o and Ha

of 0o. After reading had been taken down we turn theodolite for 22.5o clockwise

and completes all 25 points of the readings.

From data we obtain and by the help of formula, contour map can be sketched.


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Result Analysis

This is contour mapping obtain after calculating its elevation in all those 25 points

including the elevation scale in each line. Distance from one coordinate to another

coordinate is 4 meter and each of the line consists of point that the length between

1 line to another line represent 10 meter of elevation.


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Error Analysis

% Error:

¿Theodolite Distance−Distance Field∨ ¿DistanceCrossline

x100%¿

Point Theodolite Distance (BA - BB)m Field DistanceError Of Index %

A 11.5 11.314 1.617391304B 8.6 8.659 0.686046512C 8 8 0D 9 8.659 3.788888889E 12.2 11.314 7.262295082F 9 8.659 3.788888889G 5.4 5.657 4.759259259H 3.7 4 8.108108108I 5.8 5.657 2.465517241J 8.9 8.659 2.707865169K 6.9 8 15.94202899L 3.7 4 8.108108108M 0 0N 3.8 4 5.263157895O 7.9 8 1.265822785P 8.8 8.659 1.602272727Q 5.5 5.657 2.854545455R 3.9 4 2.564102564S 5.8 5.657 2.465517241T 9.7 8.659 10.73195876U 11.3 11.314 0.123893805V 8.9 8.659 2.707865169W 8 8 0X 8.9 8.659 2.707865169Y 12.8 11.314 11.609375

1. Human Error

As this is our first time doing the contouring mapping experiment, we all may not

be as good as those we did this often. Human error or personal error occur when

the practitioners are not experienced enough. Another factor that leads error to

occur is: we tend to make thing fast, without using the umbrella, sunlight too may

interfere the process of the reading.


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2. Parallax Error

Parallax error may occur when we are about to put pointers in the point. It occur

when we read the measurement in the measuring tape. This happens when our

eyes are not parallel to the reading. So it’s possible that we read the measurement

in different angle and as a result errors are made.

H. CONCLUSION

From the contour map we could see that our location of experiment have

several elevation state. There is an area where elevation is high and there

is an area where elevation is low.

Contours of different elevations cannot cross each other

The horizontal distance between any two contour lines indicates the

amount of slope and varies inversely on the amount of slope. Thus,

contours are spaced equally for uniform slope closely for steep slope

contours and widely for moderate slope.

Contour do not pass through permanent structures such as buildings

The steepest slope of terrain at any point on a contour is represented along

the normal of the contour at that point. They are perpendicular to ridge and

valley lines where they cross such lines.

I. REFERENCES

Wongsotjitro, Soetomo. Ilmu ukur tanah. 2003. Bandung: Institut Teknologi

Bandung


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