Total station assignment

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Abigayle Priscilla Osborne
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1 Total station assignment Objective: Control survey densification for detail surveying Location: Otaniemi campus, Innopoli 3 park area Equipment: Total Station (or electronic theodolite) and target device (prism) Methodology: traverse surveys & trigonometric levelling Output: horizontal and vertical coordinates of the control points Deliverables: traverse station descriptions, field notes, traverse computations, traverse adjustments, and rectangular coordinates of the control points (traverse and pillar- marked points) Deadline: TBD The roles of team members (change the roles from the previous assignment): assignment manager field operators for each receiver secretary Assignment instructions Every surveying project consists of four main phases: planning, field data collection, office data processing, and reporting. Below you can find the general instructions to be followed individually during each phase of the assignment. More instructions that are specific will be provided during each phase. Planning phase Do a proper field reconnaissance of the project area. Draw a sketch of the underground tunnel. Identify the location of the ground control points (traverse stations) o At least one station per each team member. Mark the new stations in the ground using wooden sticks or nails. Alternatively, o Use tape and paper markers (1 x 1 cm squares with a cross in the middle) o Drill small holes. Mark the other control points on the concrete pillars using the metal washers and construction glue o Minimum 4-5 points /40 m, alternatively on both sides of the tunnel. Develop an observation scheme o Include observation times for assignment time management. Verify and prepare the instruments. Page 1 of 9

2 Field work and data collection Assignment leader takes care of the equipment and manages the field work Prepare the instrumentation: tripod, total station, batteries, safety vests, etc. Set- up the equipment over the new traverse station, level and centre the instrument, enter the initial data o The prism constant is - 34 mm. Perform angle and distance measurement. Use repetition to eliminate possible mistakes!!! Measure first the traverse points and than the detail points. Record every time the height of the prism/reflector. Move to the next traverse station when all the measurements in the occupied station have been collected. Remove the instrument from the tripod and carry it separately by its handle or in its case. Proceed in the same manner for the new traverse station. Remember: Double check all the field recordings!!! Data processing Use a dedicated processing software (e.g., Topcon Tools v8.2.3) o Import the data collected in the field (use TS configuration when creating a new Job). Verify the heights (station and poles). Execute traverse computations o balance the angles o compute the azimuths o compute the latitudes and departures o compute the error of closure o compute the precision ratio of the survey Calculate the rectangular coordinates. Remember: Double check all the computations!!! Reporting Read the specific instructions. Include the assignment deliverables Assignment timetable Week number Description 42 Field planning: network design 43 Data collection: traverse and detail surveys 44 Data processing: traverse calculation + reporting Page 2 of 9

3 Week 42: TS assignment Specific instructions for field planning Objective: Design a control network for TS, DL and TLS measurements. Methodology: Pairs/group (recommended) Prerequisites: TBD The students should be able to carry out main preparatory activities related to the field data collection: Design a network of control points Conduct proper reconnaissance Develop an observation plan Select the appropriate instrumentation and measuring technique Identify the logistical aspects of the survey work Become familiar with various roles in group work Read the general instructions! Additional reading Schofield 1, section Surveying- 6th- Edition 2 Surveying- 6th- Edition 3 Azimuths are horizontal angles measured clockwise from a reference meridian. Bearings are horizontal angles measured from the meridian either east or west. They are quadrant dependent. In some literature, whole- Page 3 of 9 circle bearing term is used instead of azimuth.

4 Week 43: TS assignment Specific instructions for data collection Objective: Carry out a traverse survey and trigonometric levelling measurements Methodology: Pairs/group (recommended) Prerequisites: Complete the TS planning phase Read the general instructions! REMINDER: Redundancy, redundancy, redundancy! Be sure you collect redundant measurements to have a control of the quality of the field- work. Redundant measurements are a key aspect to achieve high accuracy project requirements apart of proper equipment, field measurement principles, and high professional skills. For further reading, please consult Schofield s textbook 2 as follows: Setting up Section Angle measurement Two types of angles are measured during fieldwork: horizontal angles and vertical (zenital) angles. Horizontal angles Section 5.5.1, Vertical angles Section Distance measurement Section 4.6 Traversing Section 6.2, Trigonometric leveling Section 3.15, Surveying- 6th- Edition Page 4 of 9

5 Week 44: TS assignment Specific instructions for data processing and reporting Objective: Traverse calculation, TS reporting Methodology: Pairs/group (recommended) Prerequisites: Complete previous phases of the assignment The students should obtain the final horizontal coordinates for the surveyed traverse line (i.e., TS points) and TLS control points (i.e., pillar points). In addition, the heights of all these control points can be computed using trigonometric levelling. Read the general instructions first! There are two ways to carry out the TS data processing: manually in an Excel spreadsheet or automatically using the post- processing software. Data processing in an Excel spreadsheet Follow these instructions for step- by- step calculations (e.g., in Excel): 1. Calculate the mean values for the horizontal, vertical and slope distance readings 2. Calculate the horizontal distances between the GNSS determined points using their grid coordinates 3. How these values differ from the field measurements? 4. Calculate the initial back azimuths 3 at the start of the traverse o GNSS1- GNSS2 and GNSS1- GNSS4 o Does the difference exceed the tolerance? Take the average value. 5. Calculate the final forward azimuth at the end of the traverse o GNSS3- GNSS2 and GNSS3- GNSS4 o Does the difference exceed the tolerance? Take the average value. 6. Calculate the observed horizontal angles along the traverse 7. Sum all the observed angles and calculate the misclosure 8. Balance (adjust) the angles using equal adjustment 9. Calculate the forward azimuths o Check the final forward azimuth. Is it the same value as in 3? 10. Calculate the horizontal distances 3 Azimuths are horizontal angles measured clockwise from a reference meridian. Bearings are horizontal angles measured from the meridian either east or west. They are quadrant dependent. In some literature, whole- circle bearing term is used instead of azimuth. Page 5 of 9

6 o As function of the slope distance and zenith angle 11. Calculate the coordinate differences o o o ΔE: easting differences or departures ΔN: northing differences or latitudes As function of horizontal distance and forward azimuth 12. Calculate the adjustments (δe and δn) 13. Determine the fractional linear misclosure o As fraction between the linear misclosure and total traverse horizontal length o Reject or accept traverse measurements? 14. Calculate the adjusted coordinate differences o Check: Sum up all the values. Is the sum zero? 15. Calculate the final coordinates Data processing using Topcon Tools post- processing software When using commercial software package, such as Topcon Tools, all these steps are done automatically (expecting 1-3). However, the user has to import the field measurements. Create new job 1. Start Topcon Tools o Start > All Programs > Topcon > Topcon Tools v Create a new job o Select Job > New Job (CRL+C) o Job name: CampusTotalStation o Job location: use the folder you created on your flash drive for previous assignment o Configurations: TS o Select OK Job configuration 1. Set Coordinate Systems o Select Job > Job configuration (CRTL+F2) o Coordinate Systems > Setup > Projection > Europe > Finland > TM35FIN o Coordinate Systems > Setup > Coordinate type > Grid 2. Set Units o Units > Linear Unit > Meters o Units > Angular Unit > Gons o Select OK Import the GNSS control points 1. Right click on the Points tab and select Add Point o Select General tab i. Name > GNSSx (give the corresponding number) ii. Control > Horizontal (Choose Both if the vertical control is to be included) o Select Coordinates tab i. Grid Northing (m) > Page 6 of 9

7 o ii. Grid Easting (m) > iii. Elevation (m) > Select Adjustment tab i. Std Dev n (m) > ii. Std Dev e (m) > iii. Std Dev u (m) > Please notice that due to error propagation principle the accuracy information of the control points is very important when a network is densified. It happens very often that this information is disregarded and the coordinates of the control points are considered wrongly having no errors. While for some applications may not be so significant, for geodetic engineering projects few millimetres may make the difference between success or failure. Import the field measurements 1. Add the occupied station o Add > Add Manual TS Occupation o Instrument Type > TCA2003 o Select General tab i. Point Name > XXXX (Give the station where you placed the instrument) ii. Instrument Height (m) > o Select OK 2. Add the observations collected in the above mentioned station o Select Observation tab i. Point To ii. Type iii. Reflector Height (m) iv. Horizontal Circle v. Zenith Angle vi. Slope Distance (m) vii. Remove the tick from Add Next Obs if this is the last observed point o Select OK 3. Repeat step 1 and 2 for every traverse point o e.g., GNSS1, TS01, TS02, TS03, TS04, TS05, GNSS3 Compute the initial coordinates 1. Process > Compute coordinates Compute the adjusted coordinates 1. Process > Adjustment 2. Depending on the settings, the Adjustment module will run various tests: analyse repeated observations, identical points and control ties analysis. As you executed a closed traverse and there are sighted points measured from two different stations, than the software would use a network adjustment procedure. Get the job report 1. Customize the report format o Report > Report Configuration > New report > TS report Page 7 of 9

8 o Select the wanted items from the Report item templates window o Move them to the right in the Included report items window o Modify the item by selecting Options o Select the item position o Repeat the steps above for every selected item o Define the Report format 2. Produce the report o Select Execute o Select Close The report may include the following two parts: TS Report: TopconLogo, Project Summary, TS Observations, Adjustment Summary, Control Points, Adjusted Points. TS Quality Control: Topcon Logo, Project Summary, TS observation quality, Repeated observations, Failed loop closures, Adjusted Point Quality, Identical Points. Reporting When preparing the report, please use the following structure. Each section is compulsory and gives you hints what it should contain. The report should illustrate the learning objectives acquired by the participants. It is worth maximum 100 points. 1. Introduction (10 points) Give a short description of the project including location (area), purpose, date of the survey, equipment used, followed or intended specifications, etc. 2. Reconnaissance (10 points) Describe the outcomes of the reconnaissance trip in the field including identification of any existing points, final sites selection for the new stations, etc. 3. Monumentation (10 points) Explain how the traverse control stations and TLS control network were marked in the field including station description, approximate coordinates for field identification, ties to nearby objects, rubbings 4, photos, close- up view, horizon view, and general overview site map. Include the point cards in an appendix. 4. Observation scheme (10 points) Include the network design and action plan (i.e., observation plan) for performing the fieldwork from each traverse station. 4 Monuments used to mark stations in the ground have metal caps that give the name of the point and other information about the station. This information is stamped into the cap. An imprint of the cap is obtained by laying a piece of paper directly over the cap, and rubbing across the surface with the side of the pencil lead. This helps to eliminate mistakes in station identification. Page 8 of 9

9 5. Field data collection (20 points) Describe the survey measuring techniques (e.g., traverse survey and trigonometric levelling). Explain the datum in which the coordinates are given. Include the TS field log sheets and digital copies of the data files (if any). 6. Office data processing (20 points) Explain how the data processing is carried out including software used, traversing and coordinate calculations, final horizontal coordinates and heights for all surveyed points. 7. Learning experiences (20 points) Similar to the previous assignment Date: Teacher in charge: Dr. Octavian Andrei Page 9 of 9

Terrestrial Laser Scanning assignment

Terrestrial Laser Scanning assignment Objective: Underground 3D survey using terrestrial laser scanning Location: Otaniemi campus, Innopoli 3 Business Area Equipment: Faro Focus 3D Methodology: Multiple