Levelling final
- 1. SCHOOL OF ARCHITECTURE • BUILDING • DESIGN BACHELOR OF QUANTITY SURVEYING (HONOURS) QSB 60103 – SITE SURVRYING Fieldwork Report 1 Levelling Name Student ID Marks Yong Seen Yee 0315883 Yeoh Pooi Ching 0315540 Yee Algel 0315890 Yong Boon Xiong 0321754
- 2. Contents Page Introduction to Levelling ..........................................................................3 Objective.....................................................................................................6 Outline of Apparatus .................................................................................7 Levelling Results ..............................................................9 Adjusted Data (Error Distribution) ........................................................11 Discussion.................................................................................................13 Conclusion................................................................................................14 Reference ..................................................................................................15
- 3. Introduction to Levelling Levelling is the process by which differences in height between two or more points can be determined. Its purpose may be to provide heights or contours on a plan, to provide data for road cross-sections or volumes of earthworks, or to provide a level or inclined surface in the setting out of construction works. Levelling is the measurement of geodetic height using an optical levelling instrument and a level staff or rod having a numbered scale. Common levelling instruments include the spirit level, the dumpy level, the digital level, and the laser level. (Buildcivil,2013) Definition Datum - This is an arbitrary level surface to which the heights of all points are referred. This may be the National Datum (Australian Height Datum) or local datum point established on a construction site. Mean sea level (MSL) - The average (mean) height of the sea between High and Low tides Reduced Level (RL) - A distance recorded as a Height Above or below the datum. This height is in metres Benchmark - A benchmark in everyday language is a point of reference for a measurement. In surveying a benchmark is specifically any permanent marker placed by a surveyor with a precisely known vertical elevation (but not necessarily a precisely known horizontal location). Designed to be used for many projects. A Temporary benchmark (TBM) - Benchmark usually placed for a particular project. Not designed to be a reference for other projects or for long term use.
- 5. (National Ocean Service, 2007) Back-sight - A sight taken to a benchmark or temporary benchmark. (first sight taken after setting) Intermediate Sight - These are the sights taken at nominated position, known as stations. The sights are then converted to reduced levels. Foresight - This is the last sight taken before the instrument is moved during a traverse.
- 6. Objective 1. Find the elevation of a given point with respect to the given or assumed datum. 2. Establish a point at a given elevation with respect to the given or assumed datum. 3. To identify the spot relative height. 4. To identify possible errors occurred.
- 7. Outline of Apparatus a) Automatic Level - Used by land surveyor to establish points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and so transfer, measure and set heights. - The automatic level is set above a tripod accurately to a leveled condition using footscrews. (Ebay,n.d.) b) Levelling rod - A graduated wooden or alluminium rod, used with a levelling instrument to determine the difference in height between points above a datum surface. (JimTrade.com, n.d.)
- 8. c) Adjustable leg- tripod - Surveyor’s tripod is a device used to support any one of a number of surveying instruments, such as automatic level. - This tripods are more common in the construction world, especially outdoors because of generally uneven surfaces. (Ebay,n.d.) d) Spirit Level - An instrument designed to indicate whether a surface is horizontal or vertical. Used in different type of instruments carry by surveyors. (leveldevelopments, n.d.)
- 9. Levelling Results Height of Collimation Method Backsight Foresight Height of collimation Reduced level Remarks 1.170 101.170 100.000 BM 1 1.357 3.495 99.032 97.675 TP 1 1.320 1.301 99.051 97.731 TP 2 1.343 1.403 98.991 97.648 TP 3 1.504 1.460 99.035 97.531 TP 4 1.262 1.185 99.112 97.850 TP 5 1.257 1.303 99.066 97.809 TP 6 1.382 1.528 98.920 97.538 TP 7 1.215 1.160 98.975 97.760 TP 8 3.103 1.360 100.718 97.615 TP 9 1.325 0.722 101.321 99.996 TP 10 1.330 99.991 TP 11 16.238 16.247 99.991 ∑ 16.247 100.00 - -0.009 -0.009 = Arithmetical check: ∑BS - ∑FS = Last reduce level – First reduce level 16.238 – 16.247 = 99.991 – 100.000 -0.009 = -0.009 Maximum allowable error of closure, mm: +/- 12 √K K = Number of set-ups +/- 12 √11 = +/- 39.799 mm Hence, the levelling is acceptable.
- 10. Rise and FallMethod Backsight Foresight Rise Fall Reduce level Remarks 1.170 100.000 BM 1 1.357 3.495 2.325 97.675 TP 1 1.320 1.301 0.056 97.731 TP 2 1.343 1.403 0.083 97.648 TP 3 1.504 1.460 0.117 97.531 TP 4 1.262 1.185 0.319 97.850 TP 5 1.257 1.303 0.041 97.809 TP 6 1.382 1.528 0.271 97.538 TP 7 1.215 1.160 0.222 97.760 TP 8 3.103 1.360 0.145 97.615 TP 9 1.325 0.722 2.381 99.996 TP 10 1.330 0.005 99.991 TP 11 16.238 16.247 2.978 2.987 99.991 ∑ 16.247 2.987 100.000 - -0.009 -0.009 -0.009 = Arithmetical check: ∑BS - ∑FS = ∑R - ∑L = Last reduce level – First reduce level 16.238 – 16.247 = 2.978 – 2.987 = 99.991 – 100.000 -0.009 = -0.009 = -0.009 Maximum allowable error of closure, mm: +/- 12 √K K = Number of set-ups +/- 12 √11 = +/- 39.799 mm Hence, the levelling is acceptable.
- 11. Adjusted Data (Error Distribution) Height of Collimation Method Backsight Foresight Height of collimation Reduced level Adjustment Adjusted Reduce Level Remarks 1.170 101.170 100.000 +0.000 100.000 BM 1 1.357 3.495 99.032 97.675 +0.0008 97.676 TP 1 1.320 1.301 99.051 97.731 +0.0016 97.733 TP 2 1.343 1.403 98.991 97.648 +0.0024 97.650 TP 3 1.504 1.460 99.035 97.531 +0.0032 97.534 TP 4 1.262 1.185 99.112 97.850 +0.0040 97.854 TP 5 1.257 1.303 99.066 97.809 +0.0048 97.814 TP 6 1.382 1.528 98.920 97.538 +0.0056 97.544 TP 7 1.215 1.160 98.975 97.760 +0.0064 97.766 TP 8 3.103 1.360 100.718 97.615 +0.0072 97.622 TP 9 1.325 0.722 101.321 99.996 +0.0080 100.004 TP 10 1.330 99.991 +0.0088 100.000 TP 11 16.238 16.247 99.991 ∑ 16.247 100.00 - -0.009 -0.009 = Correction = (99.991 - 100.000) / 11 = - 0.009 / 11 = - 0.0008 m
- 12. Rise and Fall Method Backsight Foresight Rise Fall Reduce level Adjustment Adjusted Reduce Level Remarks 1.170 100.000 +0.000 100.000 BM 1 1.357 3.495 2.325 97.675 +0.0008 97.676 TP 1 1.320 1.301 0.056 97.731 +0.0016 97.733 TP 2 1.343 1.403 0.083 97.648 +0.0024 97.650 TP 3 1.504 1.460 0.117 97.531 +0.0032 97.534 TP 4 1.262 1.185 0.319 97.850 +0.0040 97.854 TP 5 1.257 1.303 0.041 97.809 +0.0048 97.814 TP 6 1.382 1.528 0.271 97.538 +0.0056 97.544 TP 7 1.215 1.160 0.222 97.760 +0.0064 97.766 TP 8 3.103 1.360 0.145 97.615 +0.0072 97.622 TP 9 1.325 0.722 2.381 99.996 +0.0080 100.004 TP 10 1.330 0.005 99.991 +0.0088 100.000 TP 11 16.238 16.247 2.978 2.987 99.991 ∑ 16.247 2.987 100.000 - -0.009 -0.009 -0.009 = Correction = (99.991 - 100.000) / 11 = - 0.009 / 11 = - 0.0008 m
- 13. Discussion In this field work, the reduce level of the Bench Mark (BM) 1 is given which is 100.000m. Therefore, the reading of the backsight (BS) and the reading of the foresight (FS) are measured and recorded through the levelling process. This process is repeated for 10 times by shifting the auto level from one point to another point at the site. After obtaining the field data, we used both methods which are the height of collimation method and rise and fall method to calculate the reduce level of each station. For rise and fall method, the sum of the back-sights minus the sum of the foresights is equal to the sum of the rises minus the sum of the falls, and is also equal to the last reduced level minus the first reduce level. While for the height of collimation method, the sum of the back- sights minus the sum of the foresights is equal to the last reduce level minus the first reduce level. However, in this data, the final reduce level is less than the initial reduce level. Thus, there are some of the errors occurred during the levelling process. In this case, we can use error distribution method to adjust the reduce level result. After we calculated the reading, the error of disclosure is -0.0008 and the maximum allowable error of closure is +/- 39.799mm. Thus, our levelling is acceptable. To distribute the error, the correction is calculated according to the number of the instrument setups. The correction per setup is +0.0008 and is shown in the table provided in the adjusted data section.
- 14. Conclusion In conclusion, we manage to obtain the data needed by using the leveling equipment provided by our lecturer. We did this fieldwork twice because the error of misclosure in our first set of data was too large. Hence, we had decided to redo this fieldwork. Even though we had to spend more time, but in the end we managed to obtain a set of data with acceptable range of error of misclosure. After identifying the errors are in an acceptable range, we did adjustments to the data obtained by distributing the errors. We used both rise and fall method and height of collimation method to calculate the reduced level of each staff station. Then, we are able to complete our fieldwork report with this complete set of data.
- 15. Reference 1.) Levelling and surveying. (n.d.). Levelling and surveying. (Website) Retrieved from http://moodle.najah.edu/pluginfile.php/47165/mod_resource/content/0/Levelling_2.pdf3 2.) Manchester 1824. (n.d.). Surveying: Using a level. (Website) Retrieve from http://media.humanities.manchester.ac.uk/humanities/flash/HumeL046_FionaSmyth_SED_2/ surveying/surveying.html 3.) Engineersupply. (n.d.). automatic levels. (Website) Retrieved from http://www.engineersupply.com/automatic-levels.aspx 4.) Dictionary of Construction.com. (n.d.). Leveling rod. (Website) Retrieved from http://www.dictionaryofconstruction.com/definition/leveling-rod.html 5.) Environmental Field Techniques. (n.d.). Surveying 1: Differential Leveling. (Website) Retrieved from http://www.colorado.edu/geography/courses/geog_2043_f01/lab01_4.html 6.) Encyclopaedia Britannica. (n.d.). Spirit Leval. (Website) Retrieved from http://global.britannica.com/technology/spirit-level