The practice of gathering and measuring data on a phenomena or an item of interest is known as data acquisition. Depending on the project’s aim, scope, and complexity, numerous approaches and techniques might be used to collect data. In this article, we will compare and contrast two common data acquisition methods: classic field surveys and laser scanning. We will discuss their benefits and drawbacks, and provide some examples of their applications.
What are Classic Field Surveys?
Classic field surveys are data acquisition methods that involve direct measurements of distances, angles, elevations, and coordinates using various instruments and tools. Some of the instruments and tools used in classic field surveys are:
Total station: A device that combines an electronic theodolite (a telescope that measures horizontal
and vertical angles) and an electronic distance meter (a device that measures distances using infrared or laser light). A total station can measure the position of a point relative to a known reference point or a coordinate system.
- Tape measure: A flexible ruler that can measure linear distances between two points.
- Level: A device that can measure the difference in elevation between two points using a bubble or a laser beam.
- Compass: A device that can measure the direction of a point relative to the magnetic north or a reference direction.
- GPS (Global Positioning System): A system that uses satellites to determine the position, velocity, and time of a receiver on the ground.
Classic field surveys can be performed by one or more surveyors who use these instruments and tools to measure and record the data manually or electronically. The data can then be processed and
analyzed using software or mathematical methods to produce maps, plans, reports, etc.
What is Laser Scanning?
Laser scanning is a data collecting process that includes utilizing a laser beam to capture the shape and size of an object or a scene in 3D digital form. A laser scanner is a device that fires a laser beam at an item or a scene and measures the time it takes for the beam to bounce back (time-of-flight technique) or looks for phase shifts in the beam (phase-shift method) to calculate the distance between the device and the target. The laser scanner can also measure the intensity or color of the
reflected beam. By moving the laser beam across the object or scene, either by rotating or translating the scanner or by using mirrors, the scanner can acquire thousands or millions of points with XYZ coordinates and intensity or color values. These points form a point cloud that represents the 3D shape of the object or scene.
Depending on the range, precision, resolution, and speed required, a variety of scanners can be used for laser scanning. Some of the types of scanners are:
- Terrestrial laser scanner: A scanner placed on a tripod or a vehicle that scans objects or sceneries from a stationary or movable location on the ground. Terrestrial laser scanners have ranges that can be short (up to 100 m), medium (up to 500 m), or long (up to several kilometers).
- Airborne laser scanner: A scanner that is mounted on an aircraft or a drone and scans objects or scenes from above. Airborne laser scanners are also known as lidar (light detection and ranging) scanners. Airborne laser scanners can cover large areas with high speed and resolution.
- Handheld laser scanner: A scanner that is held by an operator and moves about to scan items or sceneries. Handheld laser scanners are portable and simple to use, but their accuracy and resolution are lower than those of other types of scanners.
Laser scanning can provide high-quality 3D data, which may then be processed and analyzed using software to create 3D models, maps, orthophotos, digital elevation models, and so on.
Benefits and Drawbacks of Classic Field Surveys
Classic field surveys have some benefits and drawbacks compared to laser scanning. Some of them are:
Benefits:
- Classic field surveys are more accurate and reliable than laser scanning for measuring small distances and angles.
- Classic field surveys are more suitable for measuring points that are not visible from one position, such as underground features or hidden corners.
- Classic field surveys are less affected by environmental conditions, such as dust, fog, rain, or sunlight, than laser scanning.
- Classic field surveys are less expensive than laser scanning in terms of equipment cost and maintenance.
Drawbacks:
- Classic field surveys are more time-consuming and labor-intensive than laser scanning, as they require more manual measurements and calculations.
- Classic field surveys are more prone to human errors and inconsistencies than laser scanning, as they depend on the skill and judgment of the surveyors.
- Classic field surveys are more limited in the amount and type of data they can collect than laser scanning, as they can only measure discrete points and not the entire surface or volume of an object or scene.
Benefits and Drawbacks of Laser Scanning
Laser scanning has some benefits and drawbacks compared to classic field surveys. Some of them are:
Benefits:
- Laser scanning is faster and more efficient than classic field surveys, as it can capture large amounts of data in a short time and with minimal human intervention.
- Laser scanning is more accurate and consistent than classic field surveys for measuring large distances and complex shapes.
- Laser scanning is more versatile and flexible than classic field surveys, as it can measure any object or scene that is visible from the scanner’s position, regardless of its size, shape, or material.
- Laser scanning is more comprehensive and detailed than classic field surveys, as it can capture the entire surface or volume of an object or scene with high resolution and
density.
Drawbacks:
- Laser scanning is less accurate and reliable than classic field surveys for measuring small distances and angles, as it is affected by the beam divergence, noise, and occlusion.
- Laser scanning is less suitable for measuring points that are not visible from one position, such as underground features or hidden corners, as it requires multiple scans from different angles or positions to cover the whole object or scene.
- Laser scanning is more affected by environmental conditions, such as dust, fog, rain, or sunlight, than classic field surveys, as they can reduce the quality and accuracy of the data.
- Laser scanning is more expensive than classic field surveys in terms of equipment cost and maintenance, as it requires specialized devices and software.
Examples of Applications
Classic field surveys and laser scanning can be applied in various fields and industries that require data acquisition. Some of the examples are:
- Surveying: Classic field surveys are used for measuring property boundaries, cadastral maps, topographic maps, etc. Laser scanning is used for measuring buildings, bridges, tunnels, monuments, etc.
- Engineering: Classic field surveys are used for designing and constructing roads, railways, pipelines, dams, etc. Laser scanning is used for inspecting and monitoring structures, deformations, cracks, etc.
- Archaeology: Classic field surveys are used for mapping archaeological sites, artifacts, tombs, etc. Laser scanning is used for creating 3D models and reconstructions of archaeological objects and scenes.
- Forestry: Classic field surveys are used for measuring tree heights, diameters, volumes, etc. Laser scanning is used for estimating forest biomass, canopy structure, carbon sequestration, etc.
- Mining: Classic field surveys are used for measuring ore deposits, mine shafts, tunnels, etc. Laser scanning is used for assessing mine safety, stability, productivity, etc.
Conclusion
Classic field surveys and laser scanning are two common data acquisition methods that have different benefits and drawbacks. Classic field surveys are more accurate and reliable for measuring small distances and angles, less affected by environmental conditions, and less expensive than laser scanning. Traditional field surveys, on the other hand, are more time-consuming and labor-intensive, prone to human mistakes and inconsistencies, and limited in the amount and type of data they can capture than laser scanning. Laser scanning is faster and more efficient, more accurate and consistent for measuring large distances and complex shapes, more versatile and flexible, and more comprehensive and detailed than classic field surveys. However, laser scanning is less accurate and reliable for measuring small distances and angles, less suitable for measuring points that are not visible from one position, more affected by environmental conditions, and more expensive than classic field surveys.
Both methods can be applied in various fields and industries that require data acquisition. The optimal approach is determined by the project’s objective, scope, and complexity. A mix of these strategies can sometimes yield the greatest results. For example, a total station can be used to measure the position of a laser scanner relative to a coordinate system or a reference point. A laser scanner can be used to measure the shape and size of an object or a scene that is difficult or impossible to measure with a total station.
Data acquisition is an important process that can provide valuable information and insights for various purposes and problems. Understanding the pros and limitations of various approaches and techniques allows us to select the most appropriate and effective method for collecting and measuring data.
