Browsing by Author "Maksimainen, Mikko, Dr., Aalto University, Finland"

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Point cloud reconstruction of luminance measurements
(2022) Kurkela, Matti
School of Engineering | Doctoral dissertation (article-based)
Point cloud reconstruction refers to 3D measurement methods of an object or a scene. Similarly, luminance measurements describe a method for determining the light intensity coming from an object. In point cloud reconstruction of luminance measurements, both methods are combined to produce 3D luminance point clouds. In general, the third dimension has been neglected in luminance measurements. This dissertation examined the performance of measurement equipment for measuring both the geometry and luminance of an object. The thesis improved calibration and workflows for evaluating 3D luminance measurement methods. The 3D measurement methods were terrestrial laser scanning, mobile laser scanning and photogrammetry. In order to transfer the luminance values to 3D points, the geometric and luminance calibrations of the cameras were studied in the dissertation, and measurement processes were developed. In addition, case studies demonstrated various applications and workflows related to luminance point cloud reconstruction. The results showed that luminance measurements can be combined with laser scanning and photogrammetry, which could simultaneously solve the positions and orientations of the cameras and the geometry of the object. In addition, the methods developed in the dissertation made it possible to transfer the dynamic range contained in the 16-bit luminance image to 3D points. The target luminance chosen for static road lighting luminance measurements was 0.01–2.88 cd·m-2 for a single measurement. In road lighting measurements performed with mobile laser scanning, the target luminance range of the digital single lens reflex camera ranged from 0.44 to 27.97cd·m-2, and the range of the panoramic camera system ranged from 0.99 to 8.63 cd·m-2. In static indoor luminance measurements, the dynamic range of the terrestrial laser scanner reached 4.3–443.6 cd·m-2. With the chosen luminance measurement methods, it was possible to solve the positions of the 3D measurement equipment and determine the properties of the 3D points such as position, colour, luminance, intensity and point normal. The developed luminance measurement methods expand the range of possible applications. 3D luminance measurements enable the evaluation of ergonomics, energy consumption and lighting changes in indoor spaces. Measuring road and street lighting conditions in the outdoor environment enables maintaining safety and driving comfort. 3D luminance measurements performed with mobile laser scanning enable the collection of data also from wide road and street environments.