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Lecture

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Department
Engineering
Course
ENG 2130
Professor
All Professors
Semester
Winter

Description
YORK UNIVERSITY Faculty of Engineering ENG 2120 / EATS 2620 FUNDAMENTALS OF SURVEYING: LAB 2 Submitted to: Prof. Wang Jian-Guo York University, Ontario Abstract: This lab mainly focuses on the intrinsic errors of the TRANSIT instrument. The lab splits in two parts. Both parts of this lab are fairly precise because they are being measured by very accurate instruments. On the first part we used a two peg test to measure the deviation of the TRANSIT line of sight from the true horizontal. Every student took turns measuring the distances and using this data the collimation error was calculated. On the second part of the lab we set up a circuit loop consisting of 10 stations and measured the distance between each point. Then we set up the transit in the middle of each point and students took turns measuring the back sight and fore sight of each point as we traversed the loop. We then repeated the same procedure backwards. We used the data to calculate the misclosure . Introduction: The main purpose of this lab is to introduce the instruments used in field surveying and the fundamental skills used in this field and mainly how to work with these instruments. It also focuses on the intrinsic errors attributed to the TRANSIT. The instruments used in this lab are levelling rod, TRANSIT (a type of Theodolite), Stadia and fibre glass tape. The levelling devices are used to ensure measurements are accurate and precise. The fiber glass tapes are frequently used to measure distances or lengths. Ideally, the tape is unrolled and laid across a surface between measured points. Suspending the tape in the air will inevitably cause sag, and cause errors so it is better to hold them tight and straight not to cause errors. The Stadia or levelling rod is the resolution to long distance measurements. A TRANSIT and level are used to take measurements using the stadia rod. The rod is being placed at a distance away, and measurements are read using the TRANSIT reticle, which make three reading targets. In this lab we are only using the middle reading. Calculations are made from these readings to determine the distance between the instrument and the stadia rod. Levels are used to ensure that instruments are perpendicular and in a straight line to the floor or surface when getting the data and to insure the data is accurate. The TRANSIT is placed and locked on a tripod that is height adjustable. The level on the transit was to ensure the instrument is precisely horizontal and parallel to the floor; a hand level was used to keep the stadia rod held perpendicular to the floor. Objective: To obtain skills to perform spirit levelling and checking the collimation error and misclosure of a circuit. Establishing surveying skills such as setting up a levelling line, working with the level, observing and recording measurement from the levelling rods, recording data, keeping field notes, and field sketching. Being able to analyze the data collected to calculate accuracy and error deviation. Field tasks: 1- Two peg test: • a) Identify a line(ca. 40 m) on approximately level ground and place two levelling plates at both end points, measure the length of the line and find the middle point on the line; • b)Set up the level over the middle point of the line, hold two levelling rods vertically on the levelling plates, observe the rods and record the readings; • c)Move the level to either side of the line outside close to the end point ( a few meters) and reset up the level, measure the distance between the level and the closer levelling rod, observe the levelling rods and record the readings; • d) Calculate the collimation error. 2- Spirit Levelling(a circuit): Field Scheme: a) Identify a circuit along which a group can have 6 (for three person group) or 8 (for 4 person groups) instrument setups and mark at least two points on the circuit that can be reoccupied while performing the double-run levelling; b) Each of group members should at least perform two instrument setups to practice the spirit levelling process; c) A double-run is always required in practice. Results Two Peg Test Table 1: Measurements Taken From the Midpoint Student B.S. F.S. F.S.-B.S. Vincent 1.585 1.611 0.026 Luke 1.447 1.462 0.015 Kenneth 1.415 1.441 0.026 Atena 1.481 1.512 0.031 Aaditya 1.502 1.530 0.028 Average 0.0252 Diagram 1: Experimental Setup for Two Peg Test Transit (level) Stadia rod A A B D/2 D/2 D Table 2: Measurements Taken 4m From the Back Sight Student Close Further Further – Closer Vincent 1.532 1.519 -0.013 Luke 1.501 1.482 -0.019 Kenneth 1.548 1.530 -0.018 Atena 1.453 1.434 -0.019 Aaditya 1.521 1.501 -0.020 Average -0.0178 Diagram 2: Experimental Setup for Two Peg Test Stadia rod Transit (level) A B D X D+X Collimation Error α’’ = 0.0821° (upward deviation from true horizontal) Spirit Levelling Table 3: Permissible Misclosure Nikon AP-7, SOKKIA B21, SOKKIA C300, TOPCON Zeiss Ni2 AT-G4 Permissible Misclosure 5.8 x 10 km 7.72 x 10 km (Cp) (km) Diagram 3: Circuit for Spirit Leveling A 1 2 3 8 7 4 6 5 B Table 4: 1 Traverse of the Circuit Loop Station B.S.(m) H.I. (m) F.S.(m) Elev.(m) Distance hi (m) (m) B 1.453 100.000 101.453 11.330 0.022 4 1.475 1.475 99.978 101.453 14.540 -0.002 3 1.472 1.473 99.980 101.452 22.565 0.023 2 1.491 1.495 99.957 101.448 14.262 -0.068 1 1.465 1.423 100.025 101.490 11.874 0.012 A 1.482 1.477 100.013 101.495 12.654 0.063 8 1.546 1.545 99.950 101.496 14.750 -0.007 7 1.540 1.539 99.957 101.497 18.358 -0.055 6 1.495 1.485 100.012 101.507 12.621 -0.023 5 1.485 1.472 100.035 101.520 16.750 0.007 B 1.492 100.028 Total distance = 149.704 m Calculated Misclosure (C )m= -0.028 Diagram 4: Experimental Setup for Spirit Leveling B.S. F.S. Transit (level) Stadia rod Station 1 Station A D/2 D/2 D Table 5: Elevation Differences for 1 Traverse of the Circuit Loop Station Elev. Difference B 100.000 0.022 4 99.978 -0.002 3 99.980 0.023 2 99.957 -0.068 1 100.025 0.012 A 100.013 0.063 8 99.950 -0.007 7 99.957 -0.055 6 100.012 -0.023 5 100.035 0.007 B 100.028 -0.028 nd Table 6: 2 Traverse of the Circuit Loop F.S. Distance Station B.S.(m) H.I. (m) Elev.(m) hi (m) (m) (m) B 1.473 100.000 101.473 16.750 0.013 5 1.485 1.486 99.987 101.472 12.621 0.004 6 1.491 1.489 99.983 101.474 18.358 0.006 7 1.499 1.497 99.977
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