Lab 7 - Closed Traverse Assignment (2)

CE 301 – Civil Engineering Systems Lab 7 - Closed Traverse Survey Page 1 of 4 Laboratory 7: Closed Traverse Survey Background Traversing is a practice used in surveying to determine the locations of points on a grid. A closed traverse survey may be performed to map property lines or to mark out the geometry of a construction project. Angles and distances are measured using a total station. Calculations, including corrections based on known geometry, are carried out to determine the coordinates of each surveyed point. Problem Statement The University of Texas has proposed the construction of a new building on the plot of land at the corner of San Jacinto and Dean Keeton. You have been hired to map the boundaries of the plot of land and propose a layout for the building footprint within those boundaries. You should consider the following criteria in your proposal: • The building must have a footprint of 3000 square feet. You may choose the dimensions. • The university would prefer to minimize the number of trees that must be removed for the building’s construction. Note the approximate location of trees in the area during your data collection. In your laboratory section, you will divide into teams of four. The boundaries of the plot of land have been marked out by four points, A through D. Using the procedures for a closed traverse survey, you will find the coordinates of each point on a grid system and use this to draw a map of the property. Every member of the team is expected to participate in all aspects of the closed traverse survey. Data Collection • Set up the Total Station at Point A. • Sight your total station on the marker designated as the reference North and set the horizontal angle reading to zero • Turn the total station and sight on Point D. Record the measured horizontal angle reading as the Azimuth of AD • Take a distance reading and record this as the distance from A to D • Set the horizontal angle reading to zero while still sighting on Point D • Turn the total station and sight on Point B. Record the measured horizontal angle reading as the interior angle at A • Take a distance reading and record this as the distance from A to B • Move the total station to Point B • Sight the total station on Point A and set the horizontal angle reading to zero • Take a distance reading and record this as the distance from B to A • Turn the total station and sight on Point C. Record the measured horizontal angle reading as the interior angle at B • Take a distance reading and record this as the distance from B to C • Repeat this procedure with the total station set up at points C and D

CE 301 – Civil Engineering Systems Lab 7 - Closed Traverse Survey Page 2 of 4 Data Analysis Angle Corrections • Convert angles into decimal degrees • Subtract the sum of the measured interior angles from the proper geometric total • Divide the error by the number of angles to find your correction • Subtract the angle correction from each interior angle Azimuth Calculations • Add the Azimuth of AD to the interior angle at A. This will give you the azimuth of AB. • Add 180 degrees to the Azimuth of AB; then add the interior angle at B. This will give you the Azimuth of BC. • If the resulting angle is greater than 360°, subtract 360° • Repeat this process to find the azimuths of lines CD and DA. Latitude and Departure Calculations • Use the average of the two measurements between points (such as A to B and B to A) for the length of this line in all calculations • Find the latitude for a given line with the following equation: 𝐿𝑎?𝑖???? ?? = 𝐿??𝑔?ℎ ?? × cos( ?𝑧𝑖???ℎ ?? ) The latitude is a measurement of how far north Point B is from Point A • Find the departure for a given line (such as A to B) with the following equation: ???𝑎????? ?? = 𝐿??𝑔?ℎ ?? × sin( ?𝑧𝑖???ℎ ?? ) The departure is a measurement of how far east Point B is from Point A Departure and Latitude Corrections • Sum the lengths of each line in the course. This is your perimeter. • Sum the latitudes of each line in the course. Since the course is a closed loop, you should travel as far north as you do south. The sum of your calculated latitudes is your error. • Divide the latitude error by the perimeter. • For each line, subtract a correction proportional to the length of the line as shown in the equation below: ????????? 𝐿𝑎?𝑖???? ?? = 𝐿𝑎?𝑖???? ?? − • Use the same procedure to correct the departures ∑ 𝐿𝑎?𝑖????? ∑ 𝐿??𝑔?ℎ? × 𝐿??𝑔?ℎ ?? • Correct the distance for each line using the following equation: ????????? ?𝑖??𝑎??? ?? = √????????? ???𝑎????? ?? 2 + ????????? 𝐿𝑎?𝑖???? ?? 2

CE 301 – Civil Engineering Systems Lab 7 - Closed Traverse Survey Page 4 of 4 Data Sheet Interior Angles Station Degrees Minutes Seconds A B C D Azimuth of AD: Field Notes Distances Line Length (ft) A to D A to B B to A B to C C to B C to D D to C D to A