What challenges are involved in 3D scanning and point clouds?
- How can objects, buildings, infrastructure, and sites be surveyed in three dimensions?
- How does laser scanning work, and how are millions of individual measurements compiled into a point cloud?
- What are the differences between terrestrial, mobile, and airborne laser scanning?
- How are different scans aligned to a single coordinate system?
- What factors determine the accuracy, resolution, and quality of a point cloud?
- How are large point clouds processed into usable 3D information and models for Geo-ICT applications?
During this Blended Learning course, you’ll be introduced to 3D scanning and working with point clouds. You’ll discover how laser scanners and other sensors can be used to collect large quantities of three-dimensional measurement points, allowing objects, buildings, infrastructure, and entire sites to be captured in great detail.
The focus is on the entire data chain: from performing a scan to registering, verifying, processing, and visualizing point clouds. You’ll learn how raw 3D measurement data is ultimately converted into usable geographic information.
How does 3D laser scanning work?
A laser scanner measures a large number of distances between the scanner and objects in the environment. By simultaneously recording the direction of each measurement, three-dimensional coordinates can be calculated for every measured point.
You’ll learn the basics of how different measurement principles, such as time-of-flight and phase shift, are used to determine distances. You’ll also be introduced to concepts such as scan resolution, measurement range, accuracy, and reflectivity.
A modern laser scanner can collect millions of points in a short amount of time. Together, these points form a detailed three-dimensional point cloud of the environment.
The goal is not to become a specialist in a single type of laser scanner. The focus is on understanding how 3D measurement data is collected and which factors determine the quality of a scan.
Terrestrial, Mobile, and Airborne Laser Scanning
3D scanning can be performed from various platforms. In Terrestrial Laser Scanning (TLS), the scanner remains in a fixed position during the scan. This allows for highly detailed measurements of, for example, buildings, structures, and industrial facilities.
In Mobile Laser Scanning (MLS), the scanner is mounted on a moving platform, such as a vehicle. GNSS and inertial sensors are used to determine the scanner’s position and orientation while in motion.
Airborne Laser Scanning involves surveying from an airplane, helicopter, or drone. This allows large areas to be surveyed in a short amount of time.
You will learn the differences between these methods and explore which technique is suitable for various types of applications.
From Individual Scans to a Single Point Cloud
It is usually not possible to fully scan an object or area from a single position. Therefore, multiple scans are often performed from different locations.
These individual scans must then be merged. This process is called registration. You’ll learn how corresponding points, targets, or other recognizable objects can be used to merge different scans.
In addition, the point cloud often needs to be linked to an existing coordinate system. This is called georeferencing. For example, known ground control points or GNSS measurements can be used for this purpose.
You’ll discover why proper registration and georeferencing are essential when point clouds need to be combined with other geographic data.
Quality and Accuracy of Point Clouds
A point cloud can contain millions of measurement points, but a large number of points does not automatically mean that the dataset is accurate or reliable.
You’ll learn which factors influence the quality of a laser scan. These include distance to the object, the angle of incidence of the laser beam, the reflective properties of materials, moving objects, and obstructions.
You’ll also examine point density, overlap between scans, and potential discrepancies during registration and georeferencing.
This will teach you not only to visually examine a point cloud but also to critically assess its quality and suitability for a specific application.
From Point Cloud to Usable 3D Information
A raw point cloud is usually not the final product. The data must be processed before it can be effectively used in GIS, CAD, BIM, or other applications.
You’ll be introduced to techniques for filtering, classifying, and segmenting point clouds. This allows you, for example, to distinguish between ground level, buildings, vegetation, and other objects.
You’ll also explore how to create elevation models, profiles, cross-sections, surfaces, and 3D models from point clouds.
The course covers common data formats such as LAS and LAZ, as well as methods for efficiently storing, exchanging, and processing large point clouds.
3D Scanning & Point Clouds in Practice
During the Blended Learning component, you’ll work with provided point clouds to go through the various steps from raw measurement data to usable 3D information. You’ll examine the structure and quality of datasets and process point clouds within Geo-ICT software.
You’ll work on assignments such as:
- Investigate how a laser scanner measures distances and converts them into three-dimensional points.
- Compare terrestrial, mobile, and airborne laser scanning and determine which method is suitable for different applications.
- Analyze a point cloud for point density, accuracy, noise, and missing data.
- Investigate how multiple scans are registered and linked to an existing coordinate system.
- Classify components of a provided point cloud, such as ground level, buildings, and vegetation.
- Process and visualize LAS or LAZ data and create an elevation profile, terrain model, or other 3D representation from a point cloud in QGIS.
By the end of the course, you will understand how 3D scanning works, how point clouds are constructed, and which factors influence the quality of 3D measurements. You will be able to explain how different scans are registered and georeferenced, and how raw point clouds are processed into usable 3D information for surveying, construction, infrastructure, and other Geo-ICT applications.