Tachoemetry Report

1.0 INTRODUCTION

Tacheometry is a system of rapid surveying, by which horizontal and vertical distances of points are obtained by optical measurements avoiding ordinary and slower process of measurements tape or a separate leveling instrument. There are two methods that can be apply and use for tachemeotry which are Electronic Distance Measurement (EDM) and Optic Distance Measurement (ODM). The ordinary methods of surveying with a total station, chain, and levelling instrument are fairly satisfactory when the ground is pretty clear of obstructions and not very precipitous, but it becomes extremely when the ground is covered with bush, or broken up by ravines. In this practical, we have been using total station we have been using total station which able to read distance by reflecting off a prism. There are two main steps in tachometric surveys; running a traversing around the area to be surveyed and locating details and elevations of the features in the area with reference to the traverse stations. Otherwise from the horizontal distance, this method also can give the value of the different height between of the two points. Distance measurement of horizontal and vertical by optic also known as total station. The distance of horizontal and vertical are measured by using the suitable formula. The different system also has a different measurement and adjustment. Precision distance and different height which is obtain by using tachometry method by comparing with precise distance and different of the height. All the information about the height was obtain by using traverse and leveling.

2.0 OBJECTIVE



To get the detail of the data for the certain area measurement.



To maintain or know each elevation points were measured with a total station and pole.



To get each of the points of the measured area contour measurement.



To ensure those buildings and other items in the map after is plotted using a computer.



To get the actual drawing of the measurement of each information and complete details by using SDR Mapping and Auto CAD.

3.0 THEORY Tacheometry is a system of rapid surveying, by which the positions, both horizontal and vertical, of points on the earth surface relatively to one another are determined without using a chain or tape or a separate leveling instrument. These are the two short cross hairs above and below the main cross. The distance between the two is multiplied by 100 to give the distance from point to where the staff is. It is important to understand the basic principles of survey and even more important if using sophisticated Total Station and Electronic Distance Measurers (EDMs).

Reduced Level RL = RL (Inst.) + IH (Inst. Ht) – HT (Pole Ht) ± HD (Ht Diff)

4.0 EQUIPMENT

Total Station

Measuring Tape

Tripod

Pole

Prism

Piket

5.0 PROCEDURE

Booking: 

The total station was set up at and places it at the station 2.



Set bearing to the reference station.



Pole and mini prism were used as a reference station at station 1. Then, the pole and mini prism can be used for the taken detail data such as edges of buildings.



The height for the instrument and pole was recorded.



Use the bubble level to make the pole more stabilize and easy to get the data.



The bearing was set from station 2 to 1 on the total station. Then, the reading of bearing and the difference height was recorded by form of data from the lab sheet.



Each of the detail data was taken that can see from the station 2. For example tree, drain, building and etc.



After the data was recorded at the first station. Then, move to the next station.



Repeat the step 1-9 at the next station until the work done. The height of the pole and instrument was taken.

Plotting: 

Processed the observation data by using SDR Mapping and Design or TRIMAP surveying software.



Topography and detail plan was produce using ACAD software.



Group report produce according to the format given.

6.0 ANALYSIS DATA In tacheometry survey work all the data that has been recorded in the form of geomatic lab sheet. Then, horizontal and vertical reading was taken directly from the total station instrument. Among the reading data was taken are: I.

Spot height – make contour map

II.

Isolated reading – tree, building

III.

Linear reading – road, drain, pedestrian

Based on the data obtained directly from the survey work is height of the instrument, bearing (take from traverse data), horizontal distance, and the value of ‘V’ (height different)

Reduced level Reduced level (Levelling) Reduced level = reduced level before + ∆h (rise) or Reduced level = reduced level before - ∆h (fall)

Reduced Level (Tacheometry) RL = RL (Inst.) + IH (Inst. Ht) – HT (Pole Ht) ± HD (Ht Diff)

ANALYSIS Levelling calculation (rise and fall method) Difference of height between two points: ∆ h = BS - FS If the difference (+∆h) = rise If the difference (-∆h) = fall BS 1.168 1.310

FS

∆h

Rise

1.142

0.026

1.302

1.444

1.236

0.930

1.348

1.598

1.108

1.232

1.168-1.142= +0.026 1.310-1.444= -0.134 1.302-0.930= +0.372 1.236-1.598= -0.362 1.348-1.232= +0.116 1.108-1.132= -0.024

1.132

Fall

Remarks TBM1=2.147 P1

0.134

P2

0.372

P3 0.362

P4

0.116

P1 0.024

TBM2= 2.147

Reduced level Calculated as follows: Reduced level = reduced level before + ∆h (rise) or Reduced level = reduced level before - ∆h (fall)

Rise

Fall

Reduced level 2.147

0.026 0.134 0.372 0.362 0.116 0.024

Remarks BM1=2.014

2.147+0.026=2.173

P1

2.173-0.134=2.039

P2

2.039+0.372=2.411

P3

2.411-0.362=2.049

P4

2.049+0.116=2.165

P1

2.165-0.024=2.141

TBM2=2.147

Arithmetic check ∑ BS - ∑ FS = ∑ Rise - ∑ Fall = Reduced level of last point – reduced level of first point

∑ BS = 1.168+1.310+1.302+1.236+1.348+1.108 =7.472 ∑ FS = 1.142+1.444+0.930+1.598+1.232+1.132 =7.478

∑ Rise = 0.026+0.372+0.116 =0.514 ∑ Fall = 0.134+0.362+0.024 =0.520

Therefore : ∑ BS - ∑ FS = ∑ Rise - ∑ Fall = Reduced level of last point – reduced level of first point 7.472-7.478 = 0.514-0.520 = 2.141-2.147 -0.006 = -0.006 =-0.006 True error reduced level of last point – reduced level of last bench mark with known reduced = 2.141- 2.147 = -0.006 *Arithmetic error in positive sign(+ve)

correction must be negative sign(-ve)

Arithmetic error in negative sign(-ve)

correction must be positive sign (+ve)

Permissible error *D + D mm ± 20 *D = total distance in km.

= ± 20

mm

= 7.69 true error < permissible error. Levelling work can be accepted. Correction

Correction =

=

true error total number of foresight

-0.006

= 0.001

Actual reduced level = reduced level±correction

Reduced level

Correction

Actual reduced level

2.147

0.000

2.147

2.173

0.001x1= -0.000

2.173-0.000= 2.173

P1

2.039

0.001x2= -0.000

2.039-0.000= 2.039

P2

2.411

0.001x3= -0.000

2.411-0.000= 2.411

P3

2.049

0.001x4= -0.001

2.049-0.001= 2.048

P4

2.165

0.001x5= -0.001

2.165-0.001= 2.164

P1

2.141

0.001x6= -0.001

2.141-0.001=2.140

TBM2=2.147

Reduced Level Station: RL

= RL (Inst.) + IH (Inst. Ht) – HT (Pole Ht) ± HD (Ht Diff) = 2.417 + 1.46 – 1.35 – 0.229 = 2.028

Remarks TBM1=2.147

7.0 DISCCUSSION Before the tacheometry survey work carried out around FKAAS faculty building, we do the levelling surveys to determine the height of each station. Further, these heights were used to determine the height of the important details. In the process of tacheometry survey, errors occur due to several factors. The main factor for the work traverse is the human factor. Among the most significant error is not exactly centre for the instrument and the data taken. Errors occur when devices are not accurate such as total station on a reference point or a pole erected in the correct position. This will affect the observed of horizontal angle. To reduce this error, process while set up the instrument must be done carefully and thoroughly so that the effect of the data error can be minimized. In addition, environmental factors also influence the impact of the survey traverse work. Hot weather conditions will make refraction for the long distance and the target of the prism is less and not clears. In addition, the soft ground will cause tripod move little by little and the position of the picket will changed. So, it will affect to the reading of data that has been recorded and make large error.

8.0 RECOMMENDATIONS

I.

II. III.

The bubble must be centre in the circle to make sure the Total Station and Mini Prism in stable condition while doing the tacheometric survey as well as for the theodolite and staff while doing the levelling. To make the work become easier, read the observation data other way clock wise or anti clockwise If all the data can be observed in one no need to setup the total station at all datum if all the detail has been observe. However, if the data cannot be observe the solution is we can add other control point.

9.0 CONCLUSION In conclusion, the process of surveying tacheometry, there is some recorded data when measure the height of the height of instrument total station, calculating the elevation and azimuth, or angle pole horizontally toward the observed details. We use TBM 1 is 2.147, so from this reduced level of the levelling we can get the reduced level for the RL point. Other than that, the surveyors should consider to shoot 360ᶿ from the station we set up the total when plotting at the plan. Lastly, all the data being transfer to computer for other application. We use the computer with SDR Mapping software to help us produce the tacheometry plan with the contour line detail. We also use the AutoCad software to edit and joint together all point that we have obtain from the fieldwork

10.0

APPENDIX

11.0

REFERENCES   

Modul Ukur Kejuruteraan ll, Jabatan Kejuruteraan Awam Politeknik Merlimau Modul Kejuruteraan Geomatik terbitan Universiti Tun Hussien Onn Malaysia (UTHM) Nota kuliah SAM 2023 Ukur Kejuruteraan Awam, Dr.Mushairy Mustaffar