Structured and Unstructured Point Cloud Generation

Scanning Systems for Point Cloud Generation

Different scanning systems, such as terrestrial laser scanners, mobile laser scanners, airborne laser scanners, or photogrammetric approaches, are used to capture or generate 3D point clouds. Depending on the system and application, the resulting data can be structured or unstructured. Terrestrial laser scanners typically generate structured data, while mobile scanning systems can generate both structured and unstructured data, though they are mostly unstructured. Photogrammetric or image-based 3D reconstructions (e.g., using UAVs) generate unstructured point clouds.

Structured and Unstructured Data Side-by-Side Comparison

Aspect	Structured	Unstructured
Data Organization	Points are arranged in a 2D index for each Setup typically based on consistent scan positions.	Points are not organized in a grid. They are a 1D index list with coordinates and attributes.
Typical Data Capture Methods	Terrestrial Laser Scanners (TLS)	TLS, mobile laser scanners, photogrammetry, merged datasets.
Processing	Easier to process due to the ordered structure; facilitated tasks like normal calculation and mesh generation by leveraging known relationships between neighboring points; simplified processing tasks.	Harder to process due to a lack of built-in spatial relationships, which may require additional processing, for example, fitting intermediate planes and surfaces.
Editable Registration	The registration can be modified.	The registration is considered final and non-editable.
Project Size	Typically, larger due to additional data for orientations and transformations across Setups.	Typically, smaller because there are fewer supporting files and no need for grid-related metadata.
Conversion to Other Formats	Can be converted to unstructured formats easily.	Difficult to convert back to the structured format due to loss of grid information.
Efficiency in Large Datasets	Less efficient for very large datasets; more complex data architecture.	Can be more efficient using hierarchical data structures like octrees.
Common Formats	PTG, E57, RCP/RCS (can be structured).	LGSx, LAS, LAZ, PTS, E57, RCP.
Typical Applications	Terrestrial laser scanning (for example, architecture, construction, land surveys).	Terrestrial laser scanning, mobile mapping, photogrammetry, image-based 3D reconstructions.