Surveying Unit 3 Errors Values Observations

Surveying

1. 23 CE 202T Surveying Unit III CONTROL SURVEYING AND ADJUSTMENT BE Civil Engineering 2 nd Year 3 rd Semester 2024 – 25 ODD Semester 2023 – 2027 Batch Department of Civil Engineering VELAMMAL Engineering College, Surapet , Chennai T A Rajha Rajeswaran , Assistant Professor

2. UNIT III CONTROL SURVEYING AND ADJUSTMENT Horizontal And Vertical Control ---- Methods & Specifications Triangulation Baseline Satellite Stations Reduction to Centre Trigonometrical Leveling Single and Reciprocal Observations Traversing Errors Sources Precautions and Corrections Classification of Errors True and Most Probable Values Weighed Observations Principle of Least Squares Normal Equation Correlates Level Nets Adjustment Of Simple Triangulation Networks

3. UNIT III CONTROL SURVEYING AND ADJUSTMENT Class 1 Horizontal & Vertical Control ---- Methods & Specifications

4. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS CONTROL SURVEYING Introduction A control survey a survey conducted to map out the positions of existing control points in the survey area. It is a crucial step toward the accurate measurement of distance and angles in the area. to establish a control network of points, surveyors must ensure the accuracy of these points before any further surveying process can be carried out .

5. What is a Control Survey? Control surveying a method of surveying and mapping uses a set of standard survey points as reference points for all subsequent surveys. These control points are established before the primary survey work is started, typically placed in locations that are easily identifiable and can be used as reference points for all subsequent surveys. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

6. What is a Control Survey? Control points established using GPS or other precise surveying instruments these points are marked on ground with metal pins or other markers, and a reference point is established. Once the control points are established, they are used as the basis for all subsequent mapping and surveying work. All points are then measured relative to the control points. This allows for precise and accurate surveying and plotting.  23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

7. What is a Control Survey? control surveying is essential Used for a variety of purposes engineering and construction projects land mapping archaeological surveys geology, forestry , and hydrology because it is essential for any project that requires precise measurements and plotting . 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

8. What is a Control Survey? Control Surveying is a very important part of any surveyor’s job because by establishing a set of control points, surveyors can guarantee that all data collected is accurate and consistent. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

9. Horizontal control surveys A typical construction project is developed and planned in the context of coordinates. It is usual and convenient that such coordinates are derived from a network of  control points . These points are established by a  control survey  and are up to tens of kilometres apart . 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

10. Horizontal control surveys Fixed control points are usually built as  control stations (monuments)  by government agencies. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

11. Horizontal control surveys On the picture below is depicted primary triangulation network in the Netherlands made up of 77 points (mostly church towers). Considering how these reference points are being found, it so no surprise that control stations are usually established on high locations (contrary to benchmark points). 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

12. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS primary triangulation network in the Netherlands made up of 77 points (mostly church towers).

13. METHODS for establishing Horizontal control network may be established Traversing Triangulation Trilateration GPS Photogrammetry 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

14. Steps / Processes of Control Survey    The process of control survey is the process of identifying and mapping any changes in the area of interest, whether it is in a built or natural environment. 1. Doing Reconnaissance 2. Distance Measuring 3. Direction Establishment 4. Locating a Position 5. Surveying with a Total Station 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

15. Processes of Control Survey    1. Doing Reconnaissance:  The first step in the process of control survey is reconnaissance. This involves gathering information about the area of interest, including the features of the land, the current terrain, and any existing landmarks. This information is then used to develop a plan for the surveying process. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

16. Processes of Control Survey    2. Distance Measuring:  The second step in the process of the control survey is distance measuring. This involves measuring the distance between two points and determining the relative positions of those points. This can be done using a variety of tools, including a tape measure, a rangefinder, or a GPS unit. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

17. Processes of Control Survey    3. Direction Establishment : The third step in the process of the control survey is direction establishment. This involves establishing the direction of the survey line, or the direction of the line of sight. This is done by measuring the angles between two points, or by using a compass to measure the direction of the line. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

18. Processes of Control Survey    4. Locating a Position:  The fourth step in the process of the control survey is locating a position. This involves finding the exact location of a point on the ground. This can be done using a GPS unit, or by using a total station to measure the angles between a point and two other points. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

19. Processes of Control Survey    5. Surveying with a Total Station : The fifth step in the process of a control survey is surveying with a total station. This involves using a total station to measure the angle and distance between a point and two other points. This is done by measuring the angles between the points and entering the data into a computer. The computer then calculates the exact location of the point. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

20. Processes of Control Survey    The process of control survey is the process of identifying and mapping any changes in the area of interest, whether it is in a built or natural environment. 1. Doing Reconnaissance:   2. Distance Measuring: 3. Direction Establishment : 4. Locating a Position:   5. Surveying with a Total Station : 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

21. Horizontal and Vertical Control - Setting out Works - Surveying-II.mp4

22. Horizontal control surveys are used to establish coordinate systems, such as State Plane Coordinates, and are essential for accurate map-making. 2 . Vertical Control Survey: This type of control survey is used to measure the elevation of the points in the survey area

23. METHODS for establishing Horizontal control network may be established Traversing Triangulation Trilateration GPS Photogrammetry 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

24. Traversing  and  triangulation  (measuring angles of triangles) are traditional methods to find coordinates of the stations and are time consuming. Total stations (electronic equipment) can be essentially helpful for trilateration: time and personal expenses can be reduced by using this method.  23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

25. Trilateration  stands on the system of triangles, where  only lengths are measured . The other method, further reducing time expenses, is  GPS . Costs of GPS equipment are high. But affordability will likely change in the future, and GPS might become more efficient than control monuments. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

26. Traverse A traverse survey measures distances and angles (courses) between the points.  These points can serve as control stations. Other, less precise measurements, can be taken from control stations then.  Traversing is used usually for smaller areas or on areas with many obstacles.  The method is appropriate for land and property surveys as well. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

27. Types of traverses Traverses are classified as  open  and  closed . By closing the loop, we have the ability to check result against errors and blunders.  Unclosed traverse can not be checked , are not recommended and need to be taken two times to avoid blunders. What is being assumed or taken from other survey is depicted in red color in diagrams below.          Types of traverse: open and closed traverse 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

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30. Measurements Loop traverses should be measured counterclockwise.  Because it is most convenient to read interior angles from left to right. It is a fast method and blunders will be avoided likely. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

31. Data reduction (for traverses) The process of  converting all the distances and angles into coordinates is called DATA REDUCTION . 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

32. Error of closure It is not expected that data taken from a survey will close exactly. If the error on closure is acceptably small, then data are improved by corrections calculated from error. The method is explained in text further. If the error on closure exceeds acceptable limit, survey has to be repeated. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

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37. Example 1 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

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40. Triangulation Triangulation is a method based on  measuring angles using theodolite on a network of triangles .  To convert angles into coordinates, some  base  distance have to be taken too. To have a control for closure,  check base  distance is measured as well. More distances can be taken to strengthen accuracy of network. The distance of control points measured depends on purpose and can vary up to tens of kilometres . According to demanded accuracy, instrument with reading of 0.1" might be requested. The result is a network of located control points. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

41. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS Trilateration Network

42. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS Australia’s Primary Geodetic Network of TriangulationTrilateration Traversing (1986)

43. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS Trig Station Beacon ( steel beacon type )

44. Trig Station Beacon ( rock cairn type) 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

45. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS Trig Station Beacon  observing pillar type

46. In trigonometry and geometry, TRIANGULATION is the process of determining the location of a point by forming triangles to the point from known points. 23 CE 202T Surveying Ut 3 CONTROL SURVEYING AND ADJUSTMENT CLASS 1 HORIZONTAL AND VERTICAL CONTROL ---- METHODS & SPECIFICATIONS

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