Abstract
Abstract. Indoor mapping and modelling is an important research subject with application in a wide range of domains including interior design, real estate, cultural heritage conservation and restoration. There are multiple sensors applicable for 3D indoor modelling, but the laser scanning technique is frequently used because of the acquisition time, detailed information and accuracy. In this paper, the efficiency of the Maptek I-Site 8820 terrestrial scanner, which is a long-range laser scanner and the accuracy of a HMLS point cloud acquired with a mobile scanner, namely GeoSlam Zeb Horizon were tested for indoor mapping. Aula Magna “Carmen Silva” of the “Gheorghe Asachi” Technical University of Iasi is studied in the current paper since the auditorium interior creates a distinct environment that combines complex geometric structures with architectural lighting and for preserving its great cultural value, the monument has a national historical significance. The registration process of the TLS point clouds was done using two methods: a semi-automatic one with artificial targets and a completely automatic one, based on Iterative Closest Point (ICP) algorithm. The resulted TLS point cloud was analysed in relation to the HMLS point cloud by computing the M3C2 (Multiscale Model to Model Cloud Comparison), obtaining a standard deviation of 2.1 cm and by investigating the Hausdorff distances from which resulted a standard deviation (σ) of 1.6 cm. Cross-sections have been extracted from the HMLS and TLS point clouds and after comparing the sections, 80% of the sigma values are less or equal to 1 cm. The results show high potential of using HMLS and also a long-range laser scanner for 3D modelling of complex scenes, the occlusion effect in the case of TLS being only 5% of the scanned area.
Highlights
Laser scanning technique is often used for mapping complex scenes, both indoor and outdoor, the resulted point cloud being transformed into a three-dimensional (3D) model that represents with high fidelity the subject of interest, making the analysis of geometrical details easier which is, with traditional techniques, difficult to achieve
An initial alignment was performed by using the 3D conformal transformation and five common spheres, two of them representing the floor lamps with the shape of spheres located in the presidium area and three of them situated on the upper railing, the Root Mean Square Error (RMSE) being 1.4 cm
The final registration was done using the Iterative Closest Point (ICP) algorithm implemented into ―PointStudio‖ software obtaining a RMSE of 9 mm
Summary
Laser scanning technique is often used for mapping complex scenes, both indoor and outdoor, the resulted point cloud being transformed into a three-dimensional (3D) model that represents with high fidelity the subject of interest, making the analysis of geometrical details easier which is, with traditional techniques, difficult to achieve. A 3D model of an indoor complex scene obtained from a static terrestrial laser scanner (TLS) requires multiple scans to avoid occlusions and to obtain a consistent indoor scene model. When using a mobile hand-held laser scanner (HMLS), the data acquisition time is relatively short around a few minutes and is mainly influenced by the scene size. Other drawbacks of using hand-held mobile laser scanner were stated by Velas et al (2019): the sensor has to be in constant movement and is sensitive to motions in the scene
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