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SURVEY 1

3. Types of Surveys in Civil Engineering

3.3. Engineering Surveying

1. Purpose of Engineering Surveys

Engineering surveys provide critical data for the planning, design, and construction of civil engineering projects. Their purposes include:

  1. Site Layout and Alignment: To define the position of structures, roads, utilities, and other infrastructure within a construction site or project area.
  2. Elevation and Contour Measurement: To determine the relative heights (elevations) of different points, essential for grading, drainage, and foundation design.
  3. Accurate Design Implementation: To ensure that the design plans are executed correctly and that the project meets specified design criteria and alignment.
  4. Quality Control: To monitor and verify that construction progresses in line with the original design and that any deviations are quickly addressed.
  5. Regulatory Compliance: To ensure the project meets environmental, zoning, and safety regulations during the construction phase.
  6. Post-construction Monitoring: To assess the long-term stability and performance of the infrastructure, ensuring that it remains safe and functional over time.

2. Types of Engineering Surveys

There are several specific types of engineering surveys based on the requirements of the project. Each type focuses on different aspects of the project to ensure its accuracy and success.

2.1. Preliminary Survey (Feasibility Survey)

  • Purpose: Conducted before starting the actual design and construction work. It helps in evaluating the feasibility of a project and gathering initial data.
  • Scope: It provides information on the land’s physical features, the availability of utilities, and the terrain conditions.
  • Instruments: Typically, basic surveying tools such as measuring tapes, theodolites, and GPS may be used.
  • Applications: Used for assessing the site for a new building, highway, or utility project.

2.2. Route Survey (Alignment Survey)

  • Purpose: Used for the determination of the optimal alignment of infrastructure such as roads, railways, or pipelines.
  • Scope: It identifies the best route based on topography, soil conditions, and environmental factors. It also determines horizontal and vertical alignments.
  • Instruments: Total stations, GPS, and theodolites are used to measure angles and distances along the proposed route.
  • Applications: Road and highway design, railway tracks, pipeline routes.

2.3. Construction Survey

  • Purpose: Ensures that the project is constructed according to the design plan. It involves precise measurements of dimensions, alignments, and elevations.
  • Scope: Surveyors stake out the positions for foundations, utilities, and other infrastructure components to ensure they are built according to the design.
  • Instruments: Total stations, optical or laser levels, and GPS systems.
  • Applications: Foundation setting, utility placement, and building layout.

2.4. Topographic Survey

  • Purpose: Measures and maps the natural and man-made features of the land, including contours, buildings, rivers, roads, and trees.
  • Scope: Involves measuring both horizontal and vertical features, showing elevation changes and natural terrain features in a topographic map.
  • Instruments: Theodolites, total stations, GPS receivers, and level instruments.
  • Applications: Site analysis for large projects like urban development, infrastructure planning, and floodplain analysis.

2.5. As-built Survey

  • Purpose: Conducted after construction to verify that the built structure aligns with the approved design and construction plans.
  • Scope: Compares the actual construction with the original design, identifying any deviations or issues.
  • Instruments: Total stations, laser scanners, and GPS systems are typically used.
  • Applications: Verifying completed buildings, roads, bridges, or utilities.

2.6. Control Survey

  • Purpose: Establishes a network of reference points, also known as control points, that are used for all subsequent surveys within the project.
  • Scope: Provides geodetic data for large-scale surveys. It is a foundational survey that provides high-accuracy points for use in other surveys.
  • Instruments: GPS, high-precision total stations, and laser scanning.
  • Applications: Geodetic control networks, large infrastructure projects, and land subdivision.

3. Instruments Used in Engineering Surveys

The accuracy of engineering surveys depends heavily on the tools and instruments used. Common instruments used in engineering surveys include:

  1. Total Station

    • Purpose: Measures distances, angles, and elevations.
    • Functionality: A total station integrates an electronic theodolite with an EDM (electronic distance measurement) device, allowing surveyors to measure angles and distances with high accuracy.
    • Applications: Used for most engineering surveys, including topographic, route, and construction surveys.

  2. GPS (Global Positioning System)

    • Purpose: Provides highly accurate position data based on satellite signals.
    • Functionality: GPS units can determine precise geographic coordinates of points with centimeter-level accuracy, especially with differential GPS (DGPS).
    • Applications: Used for large-scale engineering projects, particularly in remote locations or for setting up control points.

  3. Theodolite

    • Purpose: Measures horizontal and vertical angles.
    • Functionality: Theodolites are optical instruments that are used to measure angles with high precision.
    • Applications: Primarily used in triangulation and route surveys, as well as setting alignments in construction surveys.

  4. Laser Scanners

    • Purpose: Captures 3D data to generate point clouds that represent the surfaces of objects or terrain.
    • Functionality: Laser scanners are used to capture the precise 3D geometry of the terrain or structures, useful for topographic surveys and post-construction verification.
    • Applications: Used in large infrastructure projects, bridge construction, and 3D modeling.

  5. Levels

    • Purpose: Measures differences in elevation.
    • Functionality: An optical or digital level is used to measure vertical heights, ensuring that structures are built on level ground and that gradients are correctly designed.
    • Applications: Used in construction surveys for determining elevations of foundations, road grades, and drainage systems.

  6. Measuring Tapes and Chains

    • Purpose: Used for basic distance measurements.
    • Functionality: A measuring tape or chain is typically used for shorter distances and when precise electronic devices are unnecessary.
    • Applications: Often used in preliminary surveys or for smaller-scale projects.

4. Engineering Surveying Techniques

Surveying in engineering requires the use of advanced measurement techniques to ensure precision in the collected data. Here are some common techniques used in engineering surveys:

4.1. Triangulation

  • Purpose: To determine the position of points by forming a series of triangles.
  • Technique: Surveyors establish baseline points, then measure angles to create triangles. By applying trigonometry, the distances to other points are determined.
  • Application: Used for large-scale surveys such as geodetic surveys and control surveys.

4.2. Traversing

  • Purpose: A method of surveying where a series of connected lines are measured between points.
  • Technique: Traversing involves setting up instruments at one point and measuring angles and distances to successive points. This technique is useful for creating control networks or setting out construction lines.
  • Application: Commonly used in road and railway alignment, construction staking, and boundary surveys.

4.3. Leveling

  • Purpose: To measure height differences and establish a reference elevation.
  • Technique: A level instrument is used to measure the elevation of specific points. The surveyor measures the difference in height between two or more points.
  • Application: Used for foundation design, drainage, and road grading.

4.4. GPS and Geodetic Surveys

  • Purpose: To determine exact geographic locations on the Earth's surface.
  • Technique: GPS technology uses satellite signals to measure position and elevation with great accuracy. Geodetic surveys involve more advanced techniques, such as triangulation, to account for the curvature of the Earth.
  • Application: Ideal for large-scale infrastructure projects, such as highways, dams, and tunnels, and in remote areas where traditional surveying methods may not be feasible.