Surveying interview questions

Surveying is the science and art of determining the relative positions of points on, above, or below the Earth's surface and representing them on a map or plan. It is crucial in civil engineering for:

• Planning and Design: Accurate data for the design of structures, roads, bridges, etc.
• Construction: Ensuring structures are built according to design specifications.
• Land Development: Defining property boundaries and land use planning.
• Infrastructure Maintenance: Monitoring deformation and subsidence over time.

Types of surveying include:

• Land Surveying: Determines the boundaries and features of a parcel of land.
• Topographic Surveying: Maps the contours and features of the Earth's surface.
• Hydrographic Surveying: Measures and maps bodies of water.
• Cadastral Surveying: Establishes property lines and land ownership.
• Engineering Surveying: Supports the planning, design, and construction of engineering projects.
• Geodetic Surveying: Measures large areas using spherical coordinates for greater accuracy over long distances.

The main principles of surveying include:

• Working from Whole to Part: Survey large areas first and then break them down into smaller sections to control errors.
• Consistency of Measurement: Using standard units and consistent methods to ensure accuracy.
• Accuracy and Precision: Ensuring measurements are both accurate (close to true value) and precise (repeatable).
• Proper Planning: Planning the survey in advance to avoid errors and ensure efficient data collection.
• Use of Checks: Implementing checks at various stages to detect and correct errors.

Common surveying instruments include:

• Theodolite: Measures horizontal and vertical angles.
• Total Station: Combines theodolite and electronic distance measurement (EDM) for precise measurements.
• GPS (Global Positioning System): Provides location data using satellites.
• Leveling Instrument (Auto Level): Measures height differences.
• Laser Scanner: Captures detailed 3D data of the environment.
• Measuring Tape: Used for short distance measurements.
• Dumpy Level: Used for establishing points in the same horizontal plane.

A Total Station is an electronic/optical instrument used in modern surveying and building construction. It combines an electronic theodolite with an electronic distance measurement (EDM) device. It works by:

• Measuring Angles: Horizontal and vertical angles using an optical system.
• Measuring Distances: Using EDM, which calculates the distance by measuring the time taken for a laser or infrared signal to travel to a target and back.
• Recording Data: Capturing and storing data for analysis and mapping.

Leveling is the process of determining the height of one point relative to another. The steps include:

• Setting Up the Level Instrument: On a stable platform.
• Taking Back Sight (BS): Reading on a known elevation point (benchmark).
• Taking Fore Sight (FS): Reading on the point where elevation is to be determined.
• Calculating Height: Using the formula Height of Instrument (HI) = Elevation of Benchmark + BS, and then Elevation of Point = HI - FS.
• Recording Data: Noting readings and calculations in a leveling notebook.

• Plane Surveying: Assumes the Earth's surface is flat over small areas, suitable for areas less than 250 square kilometers. Used for small-scale projects like building sites and minor roadworks.
• Geodetic Surveying: Takes the Earth's curvature into account, suitable for large areas. Used for large-scale projects like national boundary surveys and long-distance infrastructure projects.

A benchmark is a fixed reference point with a known elevation used in surveying to establish other elevations. Types of benchmarks include:

• Permanent Benchmark: Established by government agencies, usually marked by a brass plate or concrete pillar.
• Temporary Benchmark: Established for a specific project and removed afterwards.
• Arbitrary Benchmark: Assigned an assumed elevation for convenience during the survey.

A traverse survey involves a series of connected lines whose lengths and angles are measured. The process includes:

• Reconnaissance: Survey the area to plan the traverse path.
• Setting Up Stations: Placing markers at key points along the traverse.
• Measuring Angles: Using a theodolite or total station at each station.
• Measuring Distances: Using a tape measure or EDM.
• Calculations: Using the measured angles and distances to compute coordinates of each station.
• Closure and Adjustment: Checking for and correcting any closure errors.

Sources of errors include:

• Instrumental Errors: Due to imperfections or maladjustment of instruments. Minimized by regular calibration and maintenance.
• Human Errors: Due to observation mistakes or recording errors. Minimized by proper training, double-checking, and using consistent methods.
• Natural Errors: Due to environmental conditions like temperature, wind, and magnetic variations. Minimized by conducting surveys under favorable conditions and applying necessary corrections