Integration of TLS and HLS Data for Non-Destructive Structural Damage Assessment of Building Structures: A Case Study of a Small Hydropower Plant.

This study demonstrates the effectiveness of integrating terrestrial laser scanning (TLS) and handheld laser scanning (HLS) for structural diagnostics. The research was conducted on a Small Hydropower Plant (SHP) in Koszalin, Poland. TLS was used to capture the general geometry of the object, while HLS operating in infrared (IR) and blue light modes enabled high-resolution documentation of local damage. Areas of interest were identified using the Surface Variation parameter, and selected zones were scanned with HLS. Both HLS modes delivered consistent results, with differences not exceeding ±0.37 mm. The IR mode proved particularly useful in constrained spaces, allowing for precise measurements without the use of reference markers. Comparative analyses of cross-sections through a major crack confirmed that both HLS modes produce repeatable results with submillimeter accuracy. Integrating TLS and HLS data resolved blind spots inherent to TLS and produced a complete point cloud preserving both global geometry and local detail. The findings confirm the applicability of this hybrid approach in assessing structural damage and highlight its relevance in civil engineering applications. The proposed workflow is effective for documenting inaccessible or complex geometries while optimizing data volume and acquisition time (R1-C10).