1 | Page Objectives To learn to apply a system approach to a plan, execute and manage a survey given specification as a group To learn and undertake site measurements and calculations using proper equations To learn how to analyze data with respect to error theory and produce scale plots To learn how to work in a team Read information from maps and plans To learn how to use the survey equipment such as total stations and auto level To learn how to interpret the data obtained and how to use the spread sheets to reduce, adjust and analyze the data
97
Embed
Land Surveying Using Auto Level, Leveling Staff and Theodolite. Recording and Analysing Obtained Readings Using AutoCAD and Excel
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1 | P a g e
Objectives
To learn to apply a system approach to a plan, execute and manage a survey given
specification as a group
To learn and undertake site measurements and calculations using proper equations
To learn how to analyze data with respect to error theory and produce scale plots
To learn how to work in a team
Read information from maps and plans
To learn how to use the survey equipment such as total stations and auto level
To learn how to interpret the data obtained and how to use the spread sheets to reduce,
adjust and analyze the data
2 | P a g e
Introduction
According to J. Uren’s and W.F.Price’s book, Surveying for Engineers, they describe surveying
as an art of determining the relative positions of different object on the surface of the earth by
measuring the horizontal distance between them and by preparing a map to any suitable scale.
Engineering surveying involves the following:
Investigating land, using computer based measuring instruments and geographical
knowledge, to work out the best position to construct bridges, tunnels and roads.
Producing up-to-date plans which form the basis for the design of a project.
Setting out a site, so that a structure is built in the correct location and to the correct
size.
Monitoring the construction process to make sure that the structure remains in the right
position and recording the final as-built position.
Providing control points by which the future movement of structures such as dam and
bridges can be monitored.
J. Uren & W.F. Price (2006)
3 | P a g e
We carried out the task at Lanjut Resort (4.210484, 101.9755766) Latitude and Longitude of the
place. We spent one week over there and one task was carried out every day. It usually began
after breakfast at 9-10am and we were usually done by 2-3pm. We had rain interruption on
Friday which was why our readings for task 4 had a little more margin of error.
The report is separated into four different tasks:
Task 1: Polar radiation survey
Task 2: Closed loop traverse survey
Task 3: Setting out of building outline (levelling)
Task 4: Curve re-alignment survey
4 | P a g e
General Introduction
A dictionary definition of engineering surveying is that:
The measurement, definition and portrayal, either digitally or graphically in the form of
maps or plans, of the physical features of, and the structures on the Earth’s surface. The
ability to understand engineering design information and from this provide dimensional
control for all stages of construction work.
So in simple words, surveying is used in engineering to measure the heights, angles and
distances between two or more points on a landmark.
Heribert Kahmen & Wolfgang Kaig (1988)
In this assignment, we have carried out four different tasks. After collecting initial results, I have
used trigonometry equations and other basic surveying formulas to calculate various different
readings and values.
I have used the basic designing skills to draw Auto Cad 2D and 3D drawings which were
required for the tasks one to four.
I have also discussed the different sources of errors which took place during the surveying and
how to improve those errors and the discussion of the accuracy of the readings obtained.
I have also noted down what was my experience from the surveying camp and the surveying
assignment which I have produced as a result. What I have learnt from the experience and how
this has expanded my knowledge of civil engineering.
5 | P a g e
Task 1
Our first task was to separate the group into 5 members each and to carry out setting out at the
main reception at Lanjut Resort.
My group consisted of the following members:
Mustapha M Hasson
Mohammed Hamza
Eslam Waheed
Piral Muhammad
Ziyadah Maccido
Working as a team, we carried out the necessary data required for the task.
Introduction of setting out
Setting out is the establishment of the marks and lines to define the position and level of the
elements for the construction work so that works may proceed with reference to them. This
process may be contrasted with the purpose of surveying which is to determine by
measurement the positions of existing features.
J. Uren & W.F. Price (2006)
6 | P a g e
We took the reading of the hotel lobby. We took measurements of all the columns at the hotel
lobby. We will use the readings to obtain X, Y and Z using trigonometry equations.
Civil engineering – The design and construction for engineering projects, such as public and
private works, such as infrastructure (roads, railways, water supply & treatment etc), pipelines,
dams & reservoirs, bridges & tunnels, and buildings.
Engineering surveying covers the detailed surveys required for design of engineering projects
(roads, bridges, dams, buildings, tunnels etc) as well as the setting out and monitoring of the
subsequent construction or structures.
C.L. Berger Sons (2010)
Construction surveying setting out involves staking out reference points & markers that will
guide the construction of new structures such as roads or buildings for subsequent construction.
Building or construction projects relates to specific structures e.g. low level; medium to high rise
buildings, stadiums; residential buildings; standard & odd shaped structures, etc. It can include
civil structures, (such as bridges, tunnels, dams, drainage facilities such as treatment plants,
pump stations) with significant structural elements involved.
C.L. Berger Sons (2010)
7 | P a g e
SURVEY TYPES
Engineering surveys
• Engineering surveys are conducted to obtain data essential for planning, estimating, locating
and layout for the various phases of projects. The objectives of engineering surveys include
obtaining preliminary data required for selecting suitable routes and sites and for preparing
structural designs, establishing a system of reference points, and marking lines, grades and
principal points.
David Allen (2010)
Principles of Surveying
• There are a few rules that apply to all categories and whenever field work is being carried out
& should be adhered to at all times.
David Allen (2010)
Accuracy
Use of instruments to measure angles, distances and level (requires techniques & procedures
to be mastered). Important to realise that Absolute precision can never be obtained, despite
ideal conditions and the use of the best equipment & techniques
Errors
Much of what is done in surveying is prone to errors
Gross (mistakes), systematic & random (unavoidable)
Mistakes arise from inattention, inexperience and carelessness. Important to adopt procedures
or independent checks that eliminate or isolate such errors. Systematic errors are those which
may exist but whose pattern and effects are known, can be monitored and compensated for by
application of appropriate corrections. (e.g. EDM distance; - also measure temp & pressure)
David Allen (2010)
Random errors are unavoidable & due to imperfections in instruments used, human elements
such as eyesight, & inconsistent conditions that cause such errors.
8 | P a g e
Survey methods
Surveys can usually be executed in several ways by a combination of instruments and methods.
Main factors to consider when deciding upon technique to be used:
Purpose & extent of the survey
Degree of accuracy required
Control of errors
Nature of the country (i.e. topography, vegetation, visibility & access issues, etc)
Use equipment which is well maintained, regularly checked and “calibrated”
Analyse acceptable error limits for each component of the survey (i.e. set the target accuracy
specification). Be aware of likely error sources; resolve existing & underlying errors (don’t
introduce new ones)
Confirm with defendable marking, measuring, recording and processing methods.
ALWAYS take check (‘redundant’) measurements.
Be careful & objective when collecting, assessing and recording measurements & data, & while
documenting and analysing results. (Don’t cook the books!!)
9 | P a g e
Setting Out
Definition
Setting out is the establishment of marks & lines to define the position & level of elements of the
construction work so that works may proceed with reference to them. This process may be
contrasted with the purpose of Surveying which is to determine by measurement the positions of
existing features.-
C.L. Berger Sons (2010)
Alternate definition is that setting out is the reverse of Surveying. (i.e. surveying is a process of
producing a plan or a map of a particular area, setting out begins with the plan and ends with
the various elements of an engineering project correctly positioned in the area.
(Uren, J. et al 2006)
Attitudes to setting out vary from site to site, with generally insufficient importance attached to
the process.
It tends to be rushed (time constraints & pressure from contractors), often leading to errors & in
some cases resultant costly corrections.
Good work practices & techniques in setting out essential to minimise errors & to ensure the
construction process proceeds smoothly.
Good knowledge is vital, as the setting out phase is one of the most important stages in any civil
engineering construction project.
Setting out aims
The aims of setting out are to position the works in their correct relative spatial and absolute
positions, & to ensure that they proceed smoothly and that their costs are minimised. (Uren,
J. et al 2006)
Chances of this aim being achieved will be greatly enhanced by the use of suitable control
methods, availability & reference to correct plans, and where good working practices are
adopted.
10 | P a g e
Two main aims:
Various elements of the scheme must be correct in all three-dimensions both relative and
absolute (i.e. correct size, plan position & reduced level).
Once set-out begins, it must proceed quickly & with little or no delay so the works can proceed
smoothly and costs can be minimised.
David Allen (2010)
Apparatus
The following apparatus were used for the first task
Traverse booking sheet
Levelling booking sheet
Total station
Prism
Tripod
Measurement tape
Field record book
Pen
Recording sheet
Staff
(Assignment Brief)
11 | P a g e
Procedure
There are three main steps to follow when setting up the total station:
Centering the total station
Levelling the total station
Elimination of parallax
The first step is to set up the tripod over the peg. The legs of the tripod are placed an equal
distance from the peg and are extended to suit the observer’s height.
The total station is then taken out of its case, and carefully placed on top of the tripod. It is
screwed onto the tripod.
The ground mark (peg) is focused now through the optical plummet. The three foot screws are
adjusted until the peg can be seen in clear focus.
The circular bubble on the upper part of the total station is now adjusted till it is centered by
adjusting the individual tripod legs.
The final step is to centre the plate level bubble which is done by adjusting the foot screws.
Once the bubble is in the center, the instrument is turned 90° and the bubble is checked again.
If it is still in the centre, then the instrument is ready for measurements to be taken.
Wilfred Schofield & Mark Breach (2007)
12 | P a g e
Fig 1.2 The drawing explains the angle we were measuring at the hotel lobby room
(Wilfred Schofield & Mark Breach (2007)
ST Line Face left Face right
13 | P a g e
Degree Minutes Seconds Degree Minutes Second
X
XA1 223 10 20 43 10 42
XA2 223 10 20 43 10 42
XD04 223 57 00 43 57 09
XD03 223 57 00 43 57 09
XD01 229 58 00 49 58 12
XD02 229 58 00 49 58 12
XB3 238 59 40 58 59 03
XB2 239 06 00 59 06 07
XB1 239 21 40 59 21 34
XB4 278 15 00 98 14 55
XB5 278 15 00 98 14 55
XC1 281 14 32 101 15 02
XC2 281 14 32 101 15 02
XD1 301 30 20 121 30 45
XD2 301 30 20 121 30 45
XE1 271 10 40 91 10 40
XE2 271 10 40 91 10 40
XF1 208 03 00 28 02 51
XF2 208 03 00 28 02 51
XG1 142 36 00 322 36 12
XG2 142 36 00 322 36 12
XH1 339 45 20 159 45 29
XH2 339 45 20 159 45 29
XI1 333 26 40 153 26 32
XI2 333 26 40 153 26 32
XJ1 347 58 20 167 58 45
XJ2 347 58 20 167 58 45
XJ3 01 25 40 181 24 55
XJ4 01 25 40 181 24 55
XJ5 22 46 00 202 46 24
XJ6 22 46 00 202 46 24
14 | P a g e
XK1 34 01 40 214 01 10
XK2 34 01 40 214 01 10
XL1 89 16 20 269 16 41
XL2 89 16 20 269 16 41
After we found the face right and face left from the site, we shall use equations to find the other
data which we need:
Mean
There are two conditions when we are finding the mean:
If face left is bigger than the face right:
𝐹𝑎𝑐𝑒 𝑙𝑒𝑓𝑡 + 𝐹𝑎𝑐𝑒 𝑟𝑖𝑔ℎ𝑡 + 180°
2
If face left is smaller than the face right:
𝐹𝑎𝑐𝑒 𝑙𝑒𝑓𝑡 + 𝐹𝑎𝑐𝑒 𝑟𝑖𝑔ℎ𝑡 − 180°
2
Mean in radians form
We use the following formula to convert the means from degrees to radians
Angle x 𝛑 𝟏𝟖𝟎°⁄
The next step is to obtain the HD which we can get by using the measuring tape. We measure
from the centre of the tripod to the point. The readings are in metres.
Calculation of WCB
Back Bearing = Forward Bearing - 180° if the forward bearing is greater than 180°
Back Bearing = Forward Bearing + 180° if the forward bearing is less than 180°
J. Uren & W.F. Price (2006)
Line Mean Reduced angle Whole circle bearing
15 | P a g e
Degree Minutes Seconds Degree Minutes Second Degree Minutes Second
XA1 223 10 31 00 00 00 00 00 00
XA2 223 10 31 00 00 00 00 00 00
XD04 223 57 4.5 00 46 33.5 00 46 33.5
XD03 223 57 4.5 00 46 33.5 00 46 33.5
XD01 229 58 06 06 47 35 06 47 35
XD02 229 58 06 06 47 35 06 47 35
XB3 238 59 21.5 15 48 50.5 15 48 50.5
XB2 239 06 3.5 15 55 32.5 15 55 32.5
XB1 239 21 37 16 11 06 16 11 06
XB4 278 14 57.5 55 04 26.5 55 04 26.5
XB5 278 14 57.5 55 04 26.5 55 04 26.5
XC1 281 14 47 58 04 16 58 04 16
XC2 281 14 47 58 04 16 58 04 16
XD1 301 30 32.5 78 20 1.5 78 20 1.5
XD2 301 30 32.5 78 20 1.5 78 20 1.5
XE1 271 10 40 48 00 09 48 00 09
XE2 271 10 40 48 00 09 48 00 09
XF1 208 02 55.5 344 52 24.5 344 52 24.5
XF2 208 02 55.5 344 52 24.5 344 52 24.5
XG1 142 36 06 279 25 35 279 25 35
XG2 142 36 06 279 25 35 279 25 35
XH1 339 45 24.5 116 34 53.5 116 34 53.5
XH2 339 45 24.5 116 34 53.5 116 34 53.5
XI1 333 26 36 110 16 05 110 16 05
XI2 333 26 36 110 16 05 110 16 05
XJ1 347 58 32.5 124 48 1.5 124 48 1.5
XJ2 347 58 32.5 124 48 1.5 124 48 1.5
XJ3 01 25 17.5 138 14 46.5 138 14 46.5
XJ4 01 25 17.5 138 14 46.5 138 14 46.5
XJ5 22 46 12 159 35 41 159 35 41
XJ6 22 46 12 159 35 41 159 35 41
XK1 34 01 25 170 50 54 170 50 54
16 | P a g e
XK2 34 01 25 170 50 54 170 50 54
XL1 89 16 30.50 226 05 59.50 226 05 59.50
XL2 89 16 30.50 226 05 59.50 226 05 59.50
The next step is to find the ∆E Easting and ∆N Northing using the following formula:
Northing ∆N Equation used
HD x Sin Angle x 𝛑 𝟏𝟖𝟎°⁄
The calculator should be in radians form
11.66 x Sin 00°46’33.50” x 𝛑 𝟏𝟖𝟎°⁄ = 11.658
8.78 x Sin 15°48’50.5” x 𝛑 𝟏𝟖𝟎°⁄ =8.447
The triangle shows the ∆N and ∆E and how it is used for the trigonometric values obtained
Easting ∆E Equation used
17 | P a g e
HD x Cos Angle x 𝛑 𝟏𝟖𝟎°⁄
The calculator should be in radians form
11.66 x Cos 00°46’33.50” x 𝛑 𝟏𝟖𝟎°⁄ = 0.15791
8.78 x Cos 15°48’50.5” x 𝛑 𝟏𝟖𝟎°⁄ = 2.3926
The triangle shows the ∆N and ∆E and how it is used for the trigonometric values obtained
After this, we shall obtain the ∆E and ∆N using last three digits of my passport number plus 100. My passport number is so for X it will be 106, Y is 100 and Z is 100.
To calculate the mean, the following equation was used:
(90° − 𝐹𝑎𝑐𝑒 𝑙𝑒𝑓𝑡) + (𝐹𝑎𝑐𝑒 𝑅𝑖𝑔ℎ𝑡 − 270°)
2
XA1
(90° − 97°16′00") + (262°42′10" − 270°)
2
= - 7°15’55”
Reduce Face Left
90° - Face Left
90° − 97°16′00"
= -7°16’00”
Reduce Face Right
𝐹𝑎𝑐𝑒 𝑅𝑖𝑔ℎ𝑡 − 270°
262°42′10" − 270°
22 | P a g e
=--7°17’50”
The next step is to obtain the vertical distance. In this case, the distance is found by the
following equation:
VD = Tan Mean Angle x Length
VD = Tan -7°15’55” x 12.2
VD = -1.555
The next step is to add the VD to 100 to find Z
VD + 100 = Z
-1.555 + 100 = Z
99.975 = Z
Reduced Face Right Reduced Face Left MEAN
23 | P a g e
7 16 0 7 15 50 7 15 55
8 43 0 8 43 20 8 43 10
2 45 0 2 45 30 2 45 15
7 27 20 7 27 10 7 27 15
7 24 20 7 24 30 7 24 25
2 41 40 2 41 10 2 41 25
2 16 20 2 16 10 2 16 15
9 47 40 9 47 40 9 47 40
2 4 0 2 3 40 2 3 50
7 49 20 7 49 30 7 49 25
1 48 0 1 47 40 1 47 50
5 41 20 5 41 50 5 41 35
6 51 20 6 51 50 6 51 35
7 40 0 7 39 30 7 39 45
9 18 0 9 18 40 9 18 20
13 43 40 13 43 10 13 43 25
24 | P a g e
16 38 34 16 38 0 16 38 17
13 29 0 13 28 50 13 28 55
16 1 40 16 1 0 16 1 20
24 22 40 24 22 30 24 22 35
29 20 0 29 20 50 29 20 25
26 14 40 26 15 0 26 14 50
31 30 40 31 30 0 31 30 20
8 49 0 8 48 20 8 48 40
10 33 40 10 33 50 10 33 45
8 40 0 8 39 20 8 39 40
5 11 40 5 11 20 5 11 30
14 31 20 14 31 40 14 31 30
9 2 40 9 2 0 9 2 20
10 29 40 10 29 50 10 29 45
6 23 20 6 23 10 6 23 15
12 7 0 12 6 10 12 6 35
14 40 0 14 40 30 14 40 15
25 | P a g e
11 51 20 11 51 20 11 51 20
14 20 40 14 20 0 14 20 20
VD = Tan Mean Angle x Length
VD = Tan -7°15’55” x 12.2
VD = -1.555
The next step is to add the VD to 100 to find Z
VD + 100 = Z
-1.555 + 100 = Z
99.975 = Z
26 | P a g e
Length HI V.D Z
100 100
12.2 101.53 -1.555 99.975
12.2 101.53 1.871 103.401
11.66 101.53 0.561 102.091
11.66 101.53 -1.526 100.004
11.8 101.53 -1.534 99.996
11.8 101.53 0.554 102.084
8.78 101.53 0.348 101.878
8.78 101.53 -1.516 100.014
11.42 101.53 -0.413 101.117
11.1 101.53 -1.525 100.005
11.1 101.53 -0.348 101.182
15.4 101.53 -1.535 99.995
15.4 101.53 1.853 103.383
11.35 101.53 -1.527 100.003
11.35 101.53 1.86 103.39
27 | P a g e
6.25 101.53 -1.526 100.004
6.25 101.53 1.868 103.398
6.42 101.53 -1.539 99.991
6.42 101.53 1.844 103.374
3.4 101.53 -1.541 99.989
3.4 101.53 1.911 103.441
3.1 101.53 -1.529 100.001
3.1 101.53 1.9 103.43
9.9 101.53 -1.535 99.995
9.9 101.53 1.846 103.376
10.1 101.53 -1.538 99.992
10.1 101.53 0.918 102.448
5.9 101.53 -1.529 100.001
5.9 101.53 0.939 102.469
8.35 101.53 -1.547 99.983
8.35 101.53 0.935 102.465
7.17 101.53 -1.538 99.992
28 | P a g e
7.17 101.53 1.877 103.407
7.3 101.53 -1.532 99.998
7.3 101.53 1.866 103.396
The height of the instrument is 1.53m.
29 | P a g e
Discussion and Analysis
The experiment was successfully carried out. We found the face right and face left of the whole
reception at Lanjut Resort and then we proceeded for the calculations part using the equations
as shown above for mean, whole circle bearing, X, Y and Z.
30 | P a g e
The precise observation of angles is dependent on the perpendicularity of the primary axes of
the total station. The plate level vial axis must be perpendicular to the vertical axis. The vertical
axis must be perpendicular to the horizontal axis. The axis of the line of sight must be
perpendicular to the horizontal axis.
There are many different types of errors which have occurred at the sight:
Instrumental : Plate level vial out of adjustment
Detection: Level instrument in two directions as per typical setup. Rotate instrument 180° from
either of these directions, and bubble should remain centred. Any mis-centering indicates that
the plate level vial axis is not perpendicular to the vertical axis.
Correction: Level instrument with bubble not centred by 1/2 of the detected error (bubble run),
or follow manufacturer's procedure for removal of error.
Horizontal axis not perpendicular to vertical axis
This error causes errors in both horizontal and vertical angles since telescope travels in inclined
plane instead of vertical plane.
Error can be removed by observing angles in both direct and reversed mode, and averaging.
Dual-axis compensators can remove this error is the instrument is properly calibrated.
Heribert Kahmen & Wolfgang Kaig (1988)
Axis of sight not perpendicular to horizontal axis
31 | P a g e
This error causes the telescope to scribe out a cone when it is plunged.
Corrected by using double-centering technique when extending a line, and by doubling
angles (measuring in both direct and reversed modes.)
Vertical indexing error
Eccentricity of the plates-Occurs when vertical axis of instrument does not coincide with centre
of plates. Compensated for by taking several readings about the plates and averaging. This
happens automatically in surveying grade instruments.
Circle graduation errors - Caused by irregularities in marking of plates. Take many reading
about the plates and average. This is generally handled by modern total stations.
Errors caused by peripheral equipment - Be sure that tripods and targets are mechanically
sound and in adjustment. Use targets that are appropriate for sight distances.
Natural errors
Wind. Vibrates tripod and target in windy condition. When this happens you can (1) protect
instrument from wind by using shield, or (2) Wait until wind speed reduces.
Temperature
It can cause uneven expansion of tripod and instrument parts resulting in instrument
mislevelling. When this happens you can shield instrument using umbrella.
Refraction
Causes bending of sight line. Avoid having sight line close to objects (within 0.5 m) that can
create microclimates such as the ground, cars, and large trees. When this cannot be done,
postpone observations until better conditions exist.
Tripod setting
32 | P a g e
Avoid situation where legs are placed on different surfaces, and extreme soft-ground
conditions. When this cannot be avoided such as in marshes and swamps, pound long wooden
stakes flush with surface and set tripod on stakes. Most total station instruments have sensors
to suspend observations when mislevelling becomes too great.
Personal errors-
Instrument not centred
Can cause observed angle to be too large or small. Carefully centre and level instrument. Size
of error is reduced when angles have long sight lengths.
Target not centred
Can cause observed angle to be too large or small. Use long sight distances to reduce effect
on observed angles.
Improper use of clamps and tangent screws
Practice in formation of good observing habits and familiarity with equipment will reduce these
errors.
Poor focusing
One of the most common errors. Be sure parallax is removed before taking observation. Avoid
different operators during observation procedure.
Overly careful sights
This is a common beginner error. Take careful sights on targets, but do not redo procedure.
Beginners tend to observe, then reobserve, then reobserve ... before taking sight. This process
results in unsettling instrument and reducing pointing accuracy. Trust your eyes.
J. Uren & W.F. Price (2006)
33 | P a g e
Autocad Drawings
Figure 1.9: 3D drawing of the Lobby Room from the top front
Fig 1.94: Another top view showing the columns and hotel reception with entrance and
door
34 | P a g e
Fig 1.95: Showing the columns and reception from front top view
Fig 1.96: Shows the columns and front reception from side top view
35 | P a g e
Fig 1.97: Shows the columns and reception from reception view
Sketches
36 | P a g e
Conclusion
So I can further conclude that the experiment was successfully carried out and all of the
requirements for this task were completed as scheduled.
I have learnt from this task on the methodology involved with setting out, how it is carried out,
and what the necessary precautions which have to be taken are and at the same time the errors
involved with setting out.
37 | P a g e
Task 2 Close loop traverse of a control survey
According to J. Uren and W.F. Price, a traverse is defined as a chain of straight lines which is
used as a basis for the measurement of details. A traverse is produced and developed by
measuring the internal angles and distances between points forming a boundary of the site. We
shall be measuring close traverse in this task, where area will be found of a piece of land. Each
of these straight lines is called a traverse leg and each point is called a traverse station.
Figure 2.0: Close Traverse
Close traverse
A close traverse begins and ends at the same point whose position is known. The closed
traverse is mostly used for locating the boundaries at lakes, woods, or grasslands.
Wilfred Schofield & Mark Breach (2007)
Open traverse
An open or free traverse contains a series of linked traverse lines which do not return to the
starting point. They are mainly used for road constructions.
Fieldwork
In a traverse, there are three stations which are considered to be of importance. The stations
are referred to as the rear station, the occupied station and the forward station.
38 | P a g e
Rear station: it is the one from which the person who is performing the traverse has just moved
to or a point to which the azimuth is known. It is the starting point.
Occupied station: it is the station at which the angle-measuring instrument is set up. This is the
point which the person is measuring.
Forward station: it is the next station which the person will measure in succession.
During the traverse, the horizontal angles, vertical angles and horizontal distances are
measured.
Fig 2.2: It shows the basic concept behind traversing
Horizontal angles: these are determined from instrument readings made at the occupied
station by sighting the instrument on the rear station and turning the instrument clockwise to the
forward station. When measuring horizontal angles, the instrument is always sighted at the
lowest visible point of the station markers designated the rear and forward stations. It is done in
order to avoid errors and have a more accurate drawing. Horizontal angles are used in
determining bearings.
Vertical angles: these are determined from instrument readings made at the occupied station
to the height of instrument on the station marker (using a staff) at the forward station. Vertical
angles are used in determining the difference in height between stations.
Distance: the distance was measured by using a 30 meters measuring tape. The distance is
very important as it helps to determine coordinates and heights.
39 | P a g e
Fig 2.4: This methodology was used for traversing
Selection of stations
First, we measure the bench mark. From there, we take our first station reading. The stations
were located in such a way that they were visible to the naked eye and visible during the
measurement of the readings. The distances were measured using the measuring tape which
was 30 meters long. A taping team was set up whose job was to take the measurement
between all the stations and record the measurement into a piece of paper. The line between
stations was cleared of obstacles so that there is no interference. The traverse legs or stations
were kept at a distance of more than 5 meters and less than 30 meters apart so that there will
be less errors in azimuth and instrument centering and pointing. Abubakar alkali kori, Ziyadah
and Hasan Arbabi formed the taping team who set up all the stations and measured the
distance using the measuring tape.
J. Uren & W.F. Price (2006)
Station markers
Traverse stations were marked by using nails and spray paints. All the stations were marked
using the letters A, B, C etc and the exact point was marked using the spray paint and nail.
Station signals
Spray paint and long wooden sticks were used to mark the stations and a sketch was drawn in
order to understand the area of the boundary.
Equipment used
40 | P a g e
The equipment used was the total station. A total station is defined as a device which in
combination with a theodolite and an EDM together with an inboard computer or
microprocessor, has the capacity to perform various computations such as determining the
horizontal and vertical components of slope distances, computing elevations and coordinates of
sighted points.
J. Uren & W.F. Price (2006)
Errors in traverse method
Inaccurate centering of the theodolite, total stations or target
Non-verticality of targets
Inaccurate bisection of targets
Parallax not eliminated
Lateral refraction, wind and atmospheric effects
Theodolite or total stations not level or not in adjustment
Incorrect use of the theodolite or total stations
Mistakes in writing the readings and bookings
41 | P a g e
Levelling work
Equipment used
Auto level is used to carry out levelling. It is set up on a tripod and a staff is used to take the
measurements. The staff bubble should be accurately centered in order to obtain a highly
accurate reading. After use, all the equipment used should be carefully stored with care.
Setting it up
Setup your tripod as level as possible, step on tripod legs to drive into the
ground.
Attach auto level to the tripod.
Adjust level so bubble is centred in vial.
Adjust recital until crosshairs are clear.
Adjust the objective lens until object you are sighting on is clear.
J. Uren & W.F. Price (2006)
Care of Auto Levels
If the instrument becomes wet leave it unpacked. Wipe down instrument, clean and dry
transport case. Pack up instrument only when it is perfectly dry. Never touch the glass
with fingers, use soft clean lint-free cloth to clean lens.
Checking Auto Level Accuracy
Set up instrument in an area that is as level as possible and which is about 65
metres long. Place two matching level rods or two pieces of strapping in the
ground about 15 meters apart with the faces toward each other. Position and
level the instrument so that the distance from the instrument to each rod is the
same measure.
Take a reading on each rod with the instrument (or mark each piece of strapping
where the crosshair is sighted).
42 | P a g e
Move transit to another spot on the line and take readings and mark both rods
again.
The difference between the marks on the rod will be the error of the instrument.
The error needs to be corrected by a competent repair technician.
Heribert Kahmen & Wolfgang Kaig (1988)
Parallax Error
It occurs when the image of the staff doesn’t fall exactly on the plane of the diaphragm or when
the focal point is not found in the plane of the diaphragm.
In our case, parallax error was avoided by using two different group members; they moved their
eyes to different parts of the eyepiece when viewing the staff held by another group member.
There was a slight change in the positions of the target and it was concluded that parallax error
is present and since it couldn’t be completely eliminated, it was found in acceptable range.
Bookings
Details of the site, work, date, observer, weather, wind, instrument and all other
important information should be recorded
Levelling sheets were printed and used for recording the measurements and all of them
were numbered accordingly in order to keep track and not get recordings mismatched
Reduced level
HPC method and Rise and fall method are used to find the reduced level. The height of the
instrument used is 1.53m.
Heribert Kahmen & Wolfgang Kaig (1988)
43 | P a g e
Apparatus used
Traverse booking sheet
Levelling booking sheet
Total station
Prism
Tripod
Automatic level
Measurement tape
Wooden peg
Field record book
Health and safety equipments
Pen
Recording sheet
Nails
Spray paint
Staff
Procedure
a. First, we set up the bench mark. By referring to it, we placed the tripod on the ground
and opened its legs. We first placed two legs into the ground and then the third one.
Each of them were equally apart from each other roughly.
b. We placed the theodolite on top of the tripod and then centred the bubbles to obtain
accurate readings. Adjust recital until crosshairs are clear.
c. We remove the black casing from the front lens and then switch on the theodolite. We
reset it to zero. The nail with the spray paint is seen using the lens on the ground and
until it is visible, the theodolite is then set up to be used.
d. We take the reading of the bench mark and the point 20 from behind. We then set it to
zero again and take the point number 2 in front.
e. We take the horizontal distance by using the measuring tape. Every group member was
assigned a different role in order to complete the task on time and more accurately.
f. The total angles for our case was 3240° since the equation is (n-2)*180°. After doing the
calculations, the angles were re-aligned while maintaining the same distance due to
errors.
44 | P a g e
Calculation of WCB and Back Bearing
We then have to calculate the Whole Circle Bearing and Back Bearing of each point. The back bearing is defined as the angle from the south line of the same point. Back Bearing = Forward Bearing - 180° if the forward bearing is greater than 180°
Back Bearing = Forward Bearing + 180° if the forward bearing is less than 180°
The whole circle bearing is added with my last two digits of passport number. My passport number is so the last two digits are 00.
45 | P a g e
46 | P a g e
Calculating Northing ∆N and Easting ∆E
Now we find the Northing and Easting using the basic trigonometry equations which have sine,
cosine and tangent together with the lengths recorded.
The WCB is converted to radians form which is found using the formula below. The calculator is
changed from degrees to radians.
Angle x 𝛑 𝟏𝟖𝟎°⁄
177°56’21.97” x 𝛑 𝟏𝟖𝟎°⁄ = 3.105
144°08’41.34” x 𝛑 𝟏𝟖𝟎°⁄ = 2.515
Northing ∆N Equation used
HD x Cos Angle x 𝛑 𝟏𝟖𝟎°⁄
The calculator should be in radians form
34.25 x cos 130°07’23.13” x 𝛑 𝟏𝟖𝟎°⁄ = -22.069
18.15 x cos 105°01’21.26” x 𝛑 𝟏𝟖𝟎°⁄ = -4.704
47 | P a g e
Easting ∆E Equation used
HD x Sin Angle x 𝛑 𝟏𝟖𝟎°⁄
The calculator should be in radians form
34.25 x sin 130°07’23.13” x 𝛑 𝟏𝟖𝟎°⁄ = 26.1918
18.15 x sin 105°01’21.26” x 𝛑 𝟏𝟖𝟎°⁄ = 17.5297
48 | P a g e
Autocad Drawing
49 | P a g e
HPC and Rise and Fall Method
There are two ways of calculating reduced levels – the rise and fall method and the height plane
collimation method.
The arithmetic checks must be done for all levelling calculations.
𝜮BS – 𝜮FS = 𝜮Rises – 𝜮Falls = Last Initial RL – First RL
When establishing the new heights of new TBMs and other important points, the BS and FS
should be taken and the rise and fall method of calculation should be used.
The HPC method of calculation can be much quicker when a lot of intermediate sights have
been taken and it is a good method to use when mapping or setting out where many readings
are often taken from a single instrument position.
A disadvantage of the HPC method is that the check on reduced levels calculated from IS can
be long and there is a tendency for it to be omitted.
Calculation checking
Height of Collimation Method
𝜮BS – 𝜮FS = Last Initial RL – First RL
27.72 – 27.73 = 100.00 – 99.99
0.01 = 0.01
Rise and Fall Method
𝜮BS – 𝜮FS = 𝜮Rises – 𝜮Falls = Last Initial RL – First RL
27.72 – 27.73 = 9.52 – 9.53 = 99.99 – 100
0.01 = 0.01 = 0.01
50 | P a g e
Discussion & Analysis
The total station.
The plate level vial axis must be perpendicular to the vertical axis.
The vertical axis must be perpendicular to the horizontal axis.
The axis of the line of sight must be perpendicular to the horizontal axis.
Errors
Instrumental -
Plate level vial out of adjustment
Detection: Level instrument in two directions as per typical setup. Rotate instrument 180° from
either of these directions, and bubble should remain centred. Any miscentering indicates that
the plate level vial axis is not perpendicular to the vertical axis.
Correction:
Level instrument with bubble miscentred by 1/2 of the detected error (bubble run), or follow
manufacturer's procedure for removal of error.
Horizontal axis not perpendicular to vertical axis
This error causes errors in both horizontal and vertical angles since telescope travels in inclined
plane instead of vertical plane.
Error can be removed by observing angles in both direct and reversed mode, and averaging.
Dual-axis compensators can remove this error is the instrument is properly calibrated.
Heribert Kahmen & Wolfgang Kaig (1988)
Axis of sight not perpendicular to horizontal axis
This error cause the telescope to scribe out a cone when it is plunged.
Corrected by using double-centering technique when extending a line, and by doubling
angles (measuring in both direct and reversed modes.)
51 | P a g e
Eccentricity of the plates-
Occurs when vertical axis of instrument does not coincide with centre of plates. Compensated
for by taking several readings about the plates and averaging. This happens automatically in
surveying grade instruments.
Heribert Kahmen & Wolfgang Kaig (1988)
Circle graduation errors –
Caused by irregularities in marking of plates. Take many reading about the plates and average.
This is generally handled by modern total stations.
Errors caused by peripheral equipment –
Be sure that tripods, tribrach, and targets are mechanically sound and in adjustment. Use
targets that are appropriate for sight distances.
Heribert Kahmen & Wolfgang Kaig (1988)
Natural errors -
Wind
Vibrates tripod and target in windy condition. When this happens you can (1) protect instrument
from wind by using shield, or (2) Wait until wind speed reduces.
Temperature
Can cause uneven expansion of tripod and instrument parts resulting in instrument mislevelling.
When this happens you can shield instrument using umbrella.
Refraction
Causes bending of sight line. Avoid having sight line close to objects (within 0.5 m) that can
create microclimates such as the ground, cars, large trees. When this cannot be done, postpone
observations until better conditions exist.
Heribert Kahmen & Wolfgang Kaig (1988)
Tripod setting
52 | P a g e
Avoid situation where legs are placed on different surfaces, and extreme soft-ground
conditions. When this cannot be avoided such as in marshes and swamps, pound long wooden
stakes flush with surface and set tripod on stakes. Most total station instruments have sensors
to suspend observations when misleveling becomes to great.
Personal errors-
Instrument miscentering
Can cause observed angle to be too large or small. Carefully centre and level instrument. Size
of error is reduced when angles have long sight lengths.
Target miscentering
Can cause observed angle to be too large or small. Use long sight distances to reduce effect
on observed angles.
Improper use of clamps and tangent screws
Practice in formation of good observing habits and familiarity with equipment will reduce these
errors.
Poor focusing
One of the most common errors. Be sure parallax is removed before taking observation. Avoid
different operators during observation procedure.
Overly careful sights
This is a common beginner error. Take careful sights on targets, but do not redo procedure.
Beginners tend to observe, then re observe, then re observe ... before taking sight. This process
results in unsettling instrument and reducing pointing accuracy. Trust your eyes.
Heribert Kahmen & Wolfgang Kaig (1988)
53 | P a g e
Sources of error in levelling
Collimation error
Collimation error is produced when sight lengths from one instrument position are not equal,
since the collimation error is proportional to the difference in these.
In our site work carried out at Lanjut Resort, I believe the collimation error was avoided to its
acceptable limits since we kept sight lengths equal, especially focusing on the BS and FS.
A two peg test was also carried out in order to check the collimation error. We first placed pegs
on both sides of the total station and then found the difference in elevation. Then, we moved the
level 30cm past both pegs and then took the readings again. There was a slight difference in
elevation from both readings and it was concluded that it is in the acceptable range.
J. Uren & W.F. Price (2006)
Compensator not functioning
To check the compensator, gently tap the total station, move the foot screw slightly off level or
push the compensator check lever to make sure whether the reading remains constant.
In our case, the compensator was functioning perfectly since the total station used was in good
condition.
Parallax
It occurs when the image of the staff doesn’t fall exactly on the plane of the diaphragm or when
the focal point is not found in the plane of the diaphragm.
In our case, parallax error was avoided by using two different group members, they moved their
eyes to different parts of the eyepiece when viewing the staff held by another group member.
There was a slight change in the positions of the target and it was concluded that parallax error
is present and since it couldn’t be completely eliminated, it was found in acceptable range.
J. Uren & W.F. Price (2006)
54 | P a g e
Defects of the staff
The total station used was fairly new so this error is eliminated from the readings. Another error
which arises from staff defects is the zero error. It usually occurs when two staffs are used for
the same series of readings, and it is advised to use only one staff for all the readings which is
what we followed for our tasks.
J. Uren & W.F. Price (2006)
Field or on-site errors
Staff not vertical
The bubble was checked before every reading was taken and it was made sure that the bubble
was in the centre. The staff is held vertically straight as well since we are measuring the vertical
height of the ground.
Unstable ground
55 | P a g e
Task three and four were carried out on the beach. The staff was inserted into soft sand which
is why there was trouble keeping the bubble on the centre for long since the sand kept the total
station and the staff move a little.
To keep the accuracy in the readings, the measurement was taken quickly.
Handling the instrument and tripod
Though constant warnings were given to other group members, someone always ended up
coming into contact with the tripod legs. To avoid this, a circle was made around the tripod and
no one was allowed to enter the circle except the one using the total station. Fingertips were
used to focus the total station and not the complete hand.
J. Uren & W.F. Price (2006)
Reading and booking errors
Readings were immediately recorded into the recording sheets and the reading was repeated
twice loud so that there is no mistake in recording the measurements taken.
Human error
Humans also tend to make error and there are three which I have experienced in survey camp
last week:
Reading the staff incorrectly
Writing the wrong value for a reading in the recording sheet
Making mistakes in calculations
J. Uren & W.F. Price (2006)
56 | P a g e
Conclusion
Overall, the traverse method was successfully completed and the margin of error obtained was
3240° - 3239°53’57.5” giving us 00°06’2.5”.
There were a lot of errors and mistakes in this task but it was successfully completed and such
a small margin of error states that from a student of civil engineering, we are on the right verge.
We worked as a team for this task and everyone was given different tasks to complete. My skills
for working as a team were tested for this task. We all made new friends and got closer to each
other individually then we were before.
The best part was that I learnt a lot from this task. It improved my knowledge on whole circle
bearing, how to obtain mean, and how to draw a closed traverse using pen and paper and in
autocad.
The autocad part was very challenging in the beginning but slowly as I managed to see some
videos on You Tube and learn from the Auto Cad help section, I managed to make the drawings
required for this task.
57 | P a g e
Task 3
The task 3 involves setting out at given points. The figure is provided and the task was to
produce the same figure on the beach and then measure the face right and face left and
levelling measurements from stations 1, 2 and 3.
The readings were then used to calculate the mean, whole circle bearing, Northing and Easting
and the x and y using last two digits of the passport number. The height of collimation method
and rise and fall method were used for the levelling calculations.
This report will explain the research methodology used, procedure, data, analysis of data,
discussion, conclusion, recommendation and reference and appendix in the order stated.
Objective
The objective of carrying out this task is to carry out:
Levelling activities
Determine the contour lines
Plot the design building in AutoCAD
Carry out Setting out on the building outline provided
Apparatus
Traverse booking sheet
Levelling booking sheet
Total station
Prism
Tripod
Automatic level
Measurement tape
Wooden peg
Field record book
Health and safety equipment
Pen
Recording sheet
Nails
Spray paint
Staff
58 | P a g e
Procedure
There are three main steps to follow when setting up the total station:
Centering the theodolite
Levelling the theodolite
Elimination of parallax
The first step is to set up the tripod over the peg. The legs of the tripod are placed an equal
distance from the peg and are extended to suit the observer’s height.
The total station is then taken out of its case, and carefully placed on top of the tripod. It is
screwed onto the tripod.
The ground mark (peg) is focused now through the optical plummet. The three foot screws are
adjusted until the peg can be seen in clear focus.
The circular bubble on the upper part of the theodolite is now adjusted till it is centered by
adjusting the individual tripod legs.
The final step is to centre the plate level bubble which is done by adjusting the foot screws.
Once the bubble is in the center, the instrument is turned 90° and the bubble is checked again.
If it is still in the centre, then the instrument is ready for measurements to be taken.
Wilfred Schofield & Mark Breach (2007)
Since we have to follow the following map, we set it out first by using the wooden pegs provided
and then carried out the measurements using the total station.
A total station can measure both horizontal and vertical distances and at the same time the
slope distances. Using the vertical angle, the total station can calculate the horizontal and
vertical distance components of the measured slope distance and display these.
59 | P a g e
A total station is used by setting it up over one end of the line and a reflector is held by the
person at the measuring point. The instrument is pointed towards the reflector and part of the
signal returns and is processed and in a few seconds, gives the slope distances with the
horizontal and vertical distances.
Wilfred Schofield & Mark Breach (2007)
After setting up the total station, the first point taken was north, 10 meters and it was marked as
point 1. After this, since our XY was 50, the next point was north 12.50 meters from point 1.
The measurements of face right and face left were taken at every point until the whole figure
was sketched out at the field using the wooden pegs and the rope was used to connect all the
points.
Wilfred Schofield & Mark Breach (2007)
Then, a contour plan was set up by establishing wooden pegs every 2 by 2 meters. The auto
level was used to carry out the levelling measurements at every point as one group member
was holding the staff.
60 | P a g e
Calculations
After taking the readings above, the next step was to calculate the reduced level and
Misclosure, and then find the corrected reduced level values. This was done using height of
collimation method and rise and fall method.
The first bench mark was taken as 102 plus last two digits of my passport number. Since my
passport number is, the TBM remained as 102. Therefore, the first HPC was 102 + 0.555 and
that is 102.555. Microsoft excel was used to insert the data and do the calculations.
To make sure there are no mistakes done, the answer was checked using the following
equation:
𝜮BS – 𝜮FS = Last Initial RL – First RL
The value obtained was 0.003 which proved that the calculation was correctly carried out and
that there were no mistakes. The error obtained is divided by the number of stations and then
the value is distributed over the stations.
Rise and Fall Method
For the rise and fall method, there is also an arithmetic equation provided which can show us
whether the equation used is correct or not.
𝜮BS – 𝜮FS = 𝜮Rises – 𝜮Falls = Last Initial RL – First RL
4.664 – 4.667 = 1.409 – 1.412 = 101.997 – 102.000
0.003 = 0.003 = 0.003
Therefore the following calculation is correct since all the values are the same.
61 | P a g e
Discussion & Analysis
Sources of error in levelling
Collimation error
Collimation error is produced when sight lengths from one instrument position are not equal,
since the collimation error is proportional to the difference in these.
In our site work carried out at Lanjut Resort, I believe the collimation error was avoided to its
acceptable limits since we kept sight lengths equal, especially focusing on the BS and FS.
A two peg test was also carried out in order to check the collimation error. We first placed pegs
on both sides of the total station and then found the difference in elevation. Then, we moved the
level 30cm past both pegs and then took the readings again. There was a slight difference in
elevation from both readings and it was concluded that it is in the acceptable range.
J. Uren & W.F. Price (2006)
Compensator not functioning
To check the compensator, gently tap the total station, move the foot screw slightly off level or
push the compensator check lever to make sure whether the reading remains constant.
In our case, the compensator was functioning perfectly since the total station used was in good
condition.
Parallax
It occurs when the image of the staff doesn’t fall exactly on the plane of the diaphragm or when
the focal point is not found in the plane of the diaphragm.
In our case, parallax error was avoided by using two different group members, they moved their
eyes to different parts of the eyepiece when viewing the staff held by another group member.
There was a slight change in the positions of the target and it was concluded that parallax error
is present and since it couldn’t be completely eliminated, it was found in acceptable range.
62 | P a g e
J. Uren & W.F. Price (2006)
Defects of the staff
The total station used was fairly new so this error is eliminated from the readings. Another error
which arises from staff defects is the zero error. It usually occurs when two staffs are used for
the same series of readings, and it is advised to use only one staff for all the readings which is
what we followed for our tasks.
J. Uren & W.F. Price (2006)
Field or on-site errors
Staff not vertical
The bubble was checked before every reading was taken and it was made sure that the bubble
was in the centre. The staff was held vertically straight as well since we are measuring the
vertical height of the ground.
Unstable ground
63 | P a g e
Task three and four were carried out on the beach. The staff was inserted into soft sand which
is why there was trouble keeping the bubble on the centre for long since the sand kept the total
station and the staff move a little.
To keep the accuracy in the readings, the measurement was taken quickly.
J. Uren & W.F. Price (2006)
Handling the instrument and tripod
Though constant warnings were given to other group members, someone always ended up
coming into contact with the tripod legs. To avoid this, a circle was made around the tripod and
no one was allowed to enter the circle except the one using the total station. Fingertips were
used to focus the total station and not the complete hand.
Reading and booking errors
Readings were immediately recorded into the recording sheets and the reading was repeated
twice loud so that there is no mistake in recording the measurements taken.
Human error
Humans also tend to make error and there are three which I have experienced in survey camp
last week:
Reading the staff incorrectly
Writing the wrong value for a reading in the recording sheet
Making mistakes in calculations
J. Uren & W.F. Price (2006)
The total station.
The plate level vial axis must be perpendicular to the vertical axis.
The vertical axis must be perpendicular to the horizontal axis.
64 | P a g e
The axis of the line of sight must be perpendicular to the horizontal axis.
C.L. Berger Sons (2010)
Errors
Instrumental -
Plate level vial out of adjustment
Detection: Level instrument in two directions as per typical setup. Rotate instrument 180° from
either of these directions, and bubble should remain centred. Any miscentering indicates that
the plate level vial axis is not perpendicular to the vertical axis.
C.L. Berger Sons (2010)
Correction:
Level instrument with bubble miscentred by 1/2 of the detected error (bubble run), or follow
manufacturer's procedure for removal of error.
Horizontal axis not perpendicular to vertical axis
This error causes errors in both horizontal and vertical angles since telescope travels in inclined
plane instead of vertical plane.
Error can be removed by observing angles in both direct and reversed mode, and averaging.
Dual-axis compensators can remove this error is the instrument is properly calibrated.
Axis of sight not perpendicular to horizontal axis
This error cause the telescope to scribe out a cone when it is plunged.
Corrected by using double-centering technique when extending a line, and by doubling
angles (measuring in both direct and reversed modes.)
C.L. Berger Sons (2010)
65 | P a g e
Eccentricity of the plates-
Occurs when vertical axis of instrument does not coincide with centre of plates. Compensated
for by taking several readings about the plates and averaging. This happens automatically in
surveying grade instruments.
Circle graduation errors –
Caused by irregularities in marking of plates. Take many reading about the plates and average.
This is generally handled by modern total stations.
Errors caused by peripheral equipment –
Be sure that tripods, tribrach, and targets are mechanically sound and in adjustment. Use
targets that are appropriate for sight distances.
C.L. Berger Sons (2010)
Natural errors -
Wind
Vibrates tripod and target in windy condition. When this happens you can (1) protect instrument
from wind by using shield, or (2) Wait until wind speed reduces.
Temperature
Can cause uneven expansion of tripod and instrument parts resulting in instrument mislevelling.
When this happens you can shield instrument using umbrella.
Refraction
66 | P a g e
Causes bending of sight line. Avoid having sight line close to objects (within 0.5 m) that can
create microclimates such as the ground, cars, and large trees. When this cannot be done,
postpone observations until better conditions exist.
C.L. Berger Sons (2010)
Tripod setting
Avoid situation where legs are placed on different surfaces, and extreme soft-ground
conditions. When this cannot be avoided such as in marshes and swamps, pound long wooden
stakes flush with surface and set tripod on stakes. Most total station instruments have sensors
to suspend observations when misleveling becomes too great.
Personal errors-
Instrument miscentering
Can cause observed angle to be too large or small. Carefully centre and level instrument. Size
of error is reduced when angles have long sight lengths.
Target miscentering
Can cause observed angle to be too large or small. Use long sight distances to reduce effect
on observed angles.
C.L. Berger Sons (2010)
Improper use of clamps and tangent screws
Practice in formation of good observing habits and familiarity with equipment will reduce these
errors.
Poor focusing
One of the most common errors. Be sure parallax is removed before taking observation. Avoid
different operators during observation procedure.
Overly careful sights
67 | P a g e
This is a common beginner error. Take careful sights on targets, but do not redo procedure.
Beginners tend to observe, then re observe, then re observe ... before taking sight. This process
results in unsettling instrument and reducing pointing accuracy. Trust your eyes.
C.L. Berger Sons (2010)
Contour drawing for task 3
68 | P a g e
Conclusion
I come to the conclusion that the error obtained was 0.03. The different sources of error were
discussed in order to explain how surveyors encounter the different errors and the best part was
that most of the errors we had experienced them at the surveying camp so it gave us a very
good description and made it easy for me to explain on the errors section.
I used Auto Cad for this task as well but it was the 2D figure which was required so I didn’t have
much trouble making it.
The Contour lines came out properly and they do not meet which is an essential requirement in
contour drawing. The Points seem to be parallel to each other.
69 | P a g e
Task 4
Road Curve
This task involves the making of a road. The survey is carried out in order to establish the points
required and to ensure that the road is properly produced. Now the making of a road curve
involves extension of the tangent lines. You can understand the drawing properly by checking
the figure below:
We are carrying out the survey in order to check the health and safety issues involved with the
road. If the proper dimensions are not used, even a small margin of errors can cause accidents
which can cost us human lives and damage of infrastructure and vehicles. In other words, it can
be the reason of major transportation crisis. This is why highway engineering is respected by
the whole engineering society because they hold one of the most difficult jobs in the world and
even a slight error is not affordable.
70 | P a g e
Total Station
Capable of measuring angles in both the
horizontal and vertical planes, slope distances
Can trigonometrically convert slope distances to
their horizontal and vertical components of distances
Can compute XYZ coordinates of points using
observations. (Z is elevation)
All information can be digitally recorded
Can be used to stake-out engineering projects using
coordinates
Can measure multiple angles and average the results
Displays measurements on liquid crystal displays
71 | P a g e
All total stations have
standards
telescopes
objective lens and focus
eyepiece lens and focus
both lenses must be focused to avoid parallax
define axis of sight
EDM
horizontal axis
vertical axis
levels (many instruments use digital levels today)
keypad
display
battery
angle measurement system
horizontal circle
vertical circle
horizontal and vertical motion screws
lock screw
tangent screw
automatic compensator to correct for mislevelment - not on all instruments
collimator - used to roughly sight on target
Communication port
optical/laser plummet
base - permit interchange of equipment with tribrach
72 | P a g e
Tribrach
It is used to level instrument. Levelling screws use left-thumb rule. That is, bubble moves
in direction of left thumb, right thumb should move in opposite direction.
Used to centre instrument over point
Axis of scope in tribrach is aligned with vertical axis of instrument using right-angle prism
Since focal distance is so short, parallax must be avoided
ONLY FINGER TIGHTEN INSTRUMENT AND TRIPOD SCREWS!
Proper Handling
Always store equipment in case when returned to locker
Wipe down instrument and leave case open if equipment is wet
Always loosen tripod screws when returning them to equipment
room. Variable humidity can cause legs to swell. This will
sometimes "lock" screws in place causing permanent damage to
tripod.
When moving equipment, always remove instrument from tripod,
lower legs, and carry instrument either in case or by handle
Always keep case closed and locked when in field
Never place instrument on tripod until legs are firmly set in ground.
When tribrach has circular bubble, remove tribrach from instrument and roughly level
and centre tribrach over point before returning instrument to tribrach.
73 | P a g e
Procedure for setup over a point
Remove tribrach from instrument in case, and place on tripod if it has an optical
plummet.
Place legs such that two are downhill and are not in the lines of sight. This will prevent
you from having to lean over legs in most instances.
Extend legs so that the shortest person in your crew can comfortably use total station
without standing on tiptoes.
Roughly centre and level tripod over point. You can use a coin or stone to check
centring. Drop it from the centre of the tripod and observe where it hits.
Place instrument on tripod if required. Make sure tribrach is centred on tripod head to
ensure maximum flexibility in centring.
Focus optical plummet eyepiece and objective lens to bring ground and centring wires
into sharp focus. Make sure parallax is removed.
Using levelling screws, centre optical plummet over point
Using adjustable legs, carefully level circular bubble.
Steps 8 & 9 should bring the instrument roughly centred and levelled over the point. If
not, repeat steps.
Use precise level to roughly level instrument.
Loosen tribrach and centre instrument over point. Be careful not to rotate instrument
when sliding on head of tripod.
Fine level instrument using precise level, and tribrach levelling screws.
Check instrument centring
Check level.
Repeat steps 10-13 until instrument is precisely centred and levelled over point. (If it
takes more than the first attempt, you are doing something wrong!)
74 | P a g e
Relationships between Distances and Angles
From Euclidean geometry we know that
S = R q
Where S is the arc length on a circle of radius R subtended by
and angle q in radian units.
Thus
1' of arc = 0.03 ft at 100 ft
1" of arc = 1 ft at 40 mi, or 0.5 m at 100 km, or 1 mm at 200 m
1" of arc = 0.000004848 radians
1 radian = 206,264.8" of arc
A traverse that requires a precision of 1:20,000 implies an angular accuracy of
Important to pick a target that matches the accuracy of your instrument, and desired resulting
angle.
Example
A chaining pin is used as a site on a station that is 100 ft from the instrument. The chaining pin
is 0.01 ft wide. It is estimated that the operator can centre the sight within ±0.005 ft, or 1/2 of the
pin. What resultant angular error can occur with this target? Would this be an appropriate target
when using an instrument that has a specified accuracy of ±3"?
75 | P a g e
Measuring Horizontal Angles
The procedure for measuring angles is dependent on the total station used.
There are two basic procedures for angle measurement.
Repetition method: This method can only be done by some instruments.
Direction method : Can be performed using any total station.
An angle must be turned at least once direct, and reverse to ensure that instrumental errors are
compensated. A set of each is known as a position.
(1DR) means an angle turned once direct and once reverse. - 1 position
(2DR) means an angle turned twice in the direct and reversed. 2 positions.
General Procedures for Measuring Angles by Repetition Method
1. With instrument at I sight on J (back sight)
2. Zero display
3. Turn instrument to K (foresight).
4. Read and record display.
5. Press button to hold value of angle on display. (Note: Not all instruments have this
button.)
6. Plunge scope, and sight J.
7. Release angular value on display by pressing button. (Again, not all instruments have
this feature.)
8. Turn instrument and sight on K.
9. Repeat steps 5-8 until desired number of turnings is obtained. (There must be an even
number of angles to correct for instrumental errors.)
10. Record final angular value.
11. Take average of final value, and compare with first recorded reading to check
consistency of angle turning. Repeat angle measurement procedure, if necessary.
76 | P a g e
General Procedure for Measuring an Angle Using the Directional Method (SMI)
1. To complete the observation of the angle and distance.
2. Sight the back sight station K and zero the instrument. For most instruments, zeroing
can be done from the SETUP soft key menu.
3. From the Setup soft key menu find the SHOTS submenu. Press SETUP, NXT, SHOTS.
4. Press the BS soft key. This will read the instrument's horizontal and zenith angles and
set the values in the BSDIR: line of the screen.
5. Sight the instrument on your foresight station K, and press SHOT from the SHOTS
submenu.
6. Plunge the scope and re sight the foresight station K. Press the SHOT soft key to read
the circle in the reverse position.
7. Re sight the back sight station J and press the BS soft key.
8. To measure the angle 2DR, press the SET1 soft key to toggle the data collector to
SET2, and repeat steps a-f.
9. Press the EVAL soft key in the SHOTS submenu. This will display the average of the
two pointing and the error. If the error is less than 1.96´DIN of your instrument accept the
shots by pressing the STPTS (store points) key. If the error is too large you can delete a
pointing and repeat the shot.
Once you willing to accept your observations press the STPTS (store points) button. The data
collector will prompt to determine if this is a traverse point (TRAVR) or a side shot (SIDES).
Press TRAVR soft key. The data collector will accept the shots, move the occupied point to
station 2 (the next station in the traverse), and the back sight point to station 1 (the previous
occupied point).
77 | P a g e
General Procedure for Measuring an Angle Using the Directional Method
1. The advantage of this method is that it allows you to sight on multiple stations with little
additional effort.
2. With instrument at P, sight on Q.
3. Zero display.
4. Turn instrument to R. and read and record display.
5. Turn instrument to S and read and record display.
6. Plunge telescope.
7. Turn instrument to sight on Q.
8. Zero display.
9. Turn instrument to R. and read and record display.
10. Turn instrument to S and read and record display.
11. Repeat step 5-9 until angle(s) are measured desired number of times.
Vertical Angles
Zenith/altitude angles are angles measured in the vertical plane.
Zenith angles have zero pointing toward the instrument's zenith.
All total stations measure zenith angles.
Altitude angles have zero pointing toward the instrument's horizon
; "+" when above the horizon and "−" when below the horizon
Altitude angles were predominant with transits older transits.
Relationship between zenith angle (z) and altitude angle (a) is
Direct mode a = 90° - z
Reversed mode a = z - 270°
Indexing error is an error caused by the zero point on the vertical circle not truly being at the
zenith.
78 | P a g e
The concept involved is that we shall increase the tangent length which allows us to
have a larger curve radius and a larger curve distance which allows for a greater
distribution of deflection angles at each given point.
All roads are designed according to road speeds. This is the reason why every road has
a different speed limit. The emphasis is given to the vehicle so it can be as comfortable
and safe with the velocity and weight that it is carrying on the specific road.
This is why, the smaller the radius of the curve, the greater is the radial force acting on
the vehicle. In our case, the radius is 20°08’45” which is normal.
In a road, we can notice something an engineer will call as a super elevation. It
shouldn’t exceed a certain limit because then the road will have more curve and the
vehicles on it will slip off the way.
Curves are aligned to provide smooth changes in direction in the form of deflection
angles that will sum up to a certain amount by the end of the curve. It is often the case
that the ratio between deflection angles and longest chord length are to be made in
such a way that the angle is small over greater distance.
The curve given for us was a horizontal curve with a constant radius.
79 | P a g e
Volume of the road curve
Now, we need to find the volume of the road curve. We shall use the figure above plus the Corr RL values to find the area and then multiply it with the chord length to find the volume.
Calculations
The formation level given for group 1 is 101.XYZ. XYZ are the last three digits of my passport number so in my case, the formation level is 101.600.
The following are the autocad drawings for the cut and fill part.
80 | P a g e
Figure 4.1 : It shows the Cut and Fill for Task 4
81 | P a g e
Figure 4.2 : Shows the cut for road curve
Figure 4.3 : Shows the cut for road curve
Figure 4.4 : Shows the cut for road curve
82 | P a g e
Figure 4.5 : Shows the cut for road curve
Figure 4.6 : Shows the cut for road curve
83 | P a g e
The drawing of the new road using the Autocad and Microsoft Office Design
Calculations for the volume
84 | P a g e
Cut and Fill
F=a1 (0.4223+0.3233
2) × 5 = 1.864m²
=a2 (0.4233+0.4733
2) × 5 = 2.239m² (Triangle 0.25m² on both sides) A1=4.103
AT1 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A1 + AT1 = 4.103 + 0.25 + 0.25 = 4.603m2
Since there are two triangles, so we add 0.25m2 twice.
E=a1 (0.3233+0.4033
2) × 5 = 1.8165m²
=a2 (0.4033+0.5833
2) × 5 = 2.4665m² A2=4.283
AT2 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A2 + AT2 = 4.283 + 0.25 + 0.25 = 4.783m2
Since there are two triangles, so we add 0.25m2 twice.
D=a1 (0.3433+0.0833
2) × 5 = 1.0665m²
=a2 (0.0833+0.4733
2) × 5 = 1.3915m² A3=2.458
85 | P a g e
AT3 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A3 + AT3 = 2.458 + 0.25 + 0.25 = 2.958m2
Since there are two triangles, so we add 0.25m2 twice.
C=a1 (0.3067+0.3600
2) × 5 = 1.6085m²
=a2 (0.36+0.37
2) × 5 = 1.825m² A4=3.4918
AT4 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A4 + AT4 = 3.4918 + 0.25 + 0.25 = 3.9918m2
Since there are two triangles, so we add 0.25m2 twice.
B=a1 (0.2867+0.35169
2) × 5 = 1.6085m²
=a2 (0.3567+0.3767
2) × 5 = 1.8335m² A5=3.442
AT5 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A5 + AT5 = 3.442 + 0.25 + 0.25 = 3.992m2
Since there are two triangles, so we add 0.25m2 twice.
86 | P a g e
A=a1 (0.0767+0.3169
2) × 5 = 0.984m
=a2 (0.3169+0.4
2) × 5 = 1.7923m
Therefore A6=2.7763
AT6 = 𝐛𝐡𝟐⁄ = 𝟎. 𝟓 𝐱 𝟏
𝟐⁄ = 𝟎. 𝟐𝟓𝐦²
A6 + AT6 = 2.7763 + 0.25 + 0.25 = 3.2763m2
Since there are two triangles, so we add 0.25m2 twice.
V1= (4.603+4.783
2) × 9= 42.237m3
V2= (4.783+2.958
2) × 9 = 34.8345m3
V3= (2.958+3.9918
2) × 9= 31.2741m3
V4= (3.9918+3.992
2) × 9= 35.9271m3
V5= (3.992+3.2763
2) × 9 = 32.70735m3
Total= V1+V2 + V3 + V4 + V5 = 𝟏𝟕𝟔. 𝟗𝟖𝟎𝟎𝟓m3
Total= ( 4.603+3.2763
2)× 45 = 𝟏𝟕𝟕. 𝟐𝟖m3
The important point to note is that since the formation level is 101.600, all the points are to cut.
This actually made it easier for me to calculate the area and the volume.
The total volume to cut is 177.28m3.
87 | P a g e
Discussion & Analysis
The total station. The plate level vial axis must be perpendicular to the vertical axis.
The vertical axis must be perpendicular to the horizontal axis.
88 | P a g e
The axis of the line of sight must be perpendicular to the horizontal axis.
Errors Instrumental -
Plate level vial out of adjustment
Detection: Level instrument in two directions as per typical setup. Rotate instrument 180° from
either of these directions, and bubble should remain centred. Any miscentering indicates that
the plate level vial axis is not perpendicular to the vertical axis.
Correction:
Level instrument with bubble miscentred by 1/2 of the detected error (bubble run), or follow
manufacturer's procedure for removal of error.
Horizontal axis not perpendicular to vertical axis
This error causes errors in both horizontal and vertical angles since telescope travels in inclined
plane instead of vertical plane.
Error can be removed by observing angles in both direct and reversed mode, and averaging.
Dual-axis compensators can remove this error is the instrument is properly calibrated.
Axis of sight not perpendicular to horizontal axis
This error cause the telescope to scribe out a cone when it is plunged.
Corrected by using double-centering technique when extending a line, and by doubling
angles (measuring in both direct and reversed modes.)
Eccentricity of the plates-
Occurs when vertical axis of instrument does not coincide with centre of plates. Compensated
for by taking several readings about the plates and averaging. This happens automatically in
surveying grade instruments.
Circle graduation errors –
Caused by irregularities in marking of plates. Take many reading about the plates and average.
This is generally handled by modern total stations.
Errors caused by peripheral equipment –
Be sure that tripods, tribrach, and targets are mechanically sound and in adjustment. Use
targets that are appropriate for sight distances.
Natural errors -
89 | P a g e
Wind
Vibrates tripod and target in windy condition. When this happens you can (1) protect instrument
from wind by using shield, or (2) Wait until wind speed reduces.
Temperature
Can cause uneven expansion of tripod and instrument parts resulting in instrument mislevelling.
When this happens you can shield instrument using umbrella.
Refraction
Causes bending of sight line. Avoid having sight line close to objects (within 0.5 m) that can
create microclimates such as the ground, cars, large trees. When this cannot be done, postpone
observations until better conditions exist.
Tripod setting
Avoid situation where legs are placed on different surfaces, and extreme soft-ground
conditions. When this cannot be avoided such as in marshes and swamps, pound long wooden
stakes flush with surface and set tripod on stakes. Most total station instruments have sensors
to suspend observations when misleveling becomes to great.
Personal errors-
Instrument miscentering
Can cause observed angle to be too large or small. Carefully centre and level instrument. Size
of error is reduced when angles have long sight lengths.
Target miscentering
Can cause observed angle to be too large or small. Use long sight distances to reduce effect
on observed angles.
Improper use of clamps and tangent screws
Practice in formation of good observing habits and familiarity with equipment will reduce these
errors.
Poor focusing
One of the most common errors. Be sure parallax is removed before taking observation. Avoid
different operators during observation procedure.
Overly careful sights
This is a common beginner error. Take careful sights on targets, but do not redo procedure.
Beginners tend to observe, then re observe, then re observe ... before taking sight. This process
results in unsettling instrument and reducing pointing accuracy. Trust your eyes.
90 | P a g e
Sources of error in levelling
Collimation error
Collimation error is produced when sight lengths from one instrument position are not equal,
since the collimation error is proportional to the difference in these.
In our site work carried out at Lanjut Resort, I believe the collimation error was avoided to its
acceptable limits since we kept sight lengths equal, especially focusing on the BS and FS.
A two peg test was also carried out in order to check the collimation error. We first placed pegs
on both sides of the total station and then found the difference in elevation. Then, we moved the
level 30cm past both pegs and then took the readings again. There was a slight difference in
elevation from both readings and it was concluded that it is in the acceptable range.
Compensator not functioning
To check the compensator, gently tap the total station, move the foot screw slightly off level or
push the compensator check lever to make sure whether the reading remains constant.
In our case, the compensator was functioning perfectly since the total station used was in good
condition.
Parallax
It occurs when the image of the staff doesn’t fall exactly on the plane of the diaphragm or when
the focal point is not found in the plane of the diaphragm.
In our case, parallax error was avoided by using two different group member, they moved their
eyes to different parts of the eyepiece when viewing the staff held by another group member.
There was a slight change in the positions of the target and it was concluded that parallax error
is present and since it couldn’t be completely eliminated, it was found in acceptable range.
91 | P a g e
Figure 4.7
Defects of the staff
The total station used was fairly new so this error is eliminated from the readings. Another error
which arises from staff defects is the zero error. It usually occurs when two staffs are used for
the same series of readings, and it is advised to use only one staff for all the readings which is
what we followed for our tasks.
Field or on-site errors
Staff not vertical
The bubble was checked before every reading was taken and it was made sure that the bubble
was in the centre. The staff was held vertically straight as well since we are measuring the
vertical height of the ground.
Unstable ground
Task three and four were carried out on the beach. The staff was inserted into soft sand which
is why there was trouble keeping the bubble on the centre for long since the sand kept the total
station and the staff move a little.
To keep the accuracy in the readings, the measurement was taken quickly.
Handling the instrument and tripod
Though constant warnings were given to other group members, someone always ended up
coming into contact with the tripod legs. To avoid this, a circle was made around the tripod and
92 | P a g e
no one was allowed to enter the circle except the one using the total station. Fingertips were
used to focus the total station and not the complete hand.
Reading and booking errors
Readings were immediately recorded into the recording sheets and the reading was repeated
twice loud so that there is no mistake in recording the measurements taken.
Human error
Humans also tend to make error and there are three which I have experienced in survey camp
last week:
Reading the staff incorrectly
Writing the wrong value for a reading in the recording sheet
Making mistakes in calculations
Conclusion Therefore I would like to conclude task 4 by saying it was properly carried out. We managed to
get all the necessary points required for the road curve. The road was properly designed and
even a slight margin of error was taken in consideration since when it comes to designing of
roads, there is always the issue of health and safety involved.
Overall Conclusion First and for all, I would like to thank Almighty Allah for giving me the strength and the courage
to complete this assignment.
Secondly, Mr Sudesh Nair for all the assistance and for being so cooperative and kind during
this period.
Thirdly all my group members and every other person who has helped or assisted me in any
way possible in completing this assignment,
All four tasks were completed on time and the measurements and recordings which were
carried out were recorded twice just to make sure that no mistake took place at all.
We used the mean value for the calculations to improve on the accuracy.
After using the equipments, they were carefully stored back in their original positions.
93 | P a g e
Team skills were practiced and all of us despite our different backgrounds, nationalities, race,
religion, and languages managed to work as a group and complete all the tasks.
All the calculations were found using equations which were found from Mr. Sudesh Notes and
Surveying text books.
Reference
Heribert Kahmen & Wolfgang Kaig (1988) Surveying. Walter de Gruyter. pp 76 – 158
C.L. Berger Sons (2010) Engineering Surveying. General Books. pp 34 – 59
Wilfred Schofield & Mark Breach (2007) Engineering Surveying. Taylor & Francis Group. pp 182
– 358
J. Uren & W.F. Price (2006) Surveying for Engineers. Palgrave Macmillan. 4th edn. pp 15 – 158