Point Cloud

Abstract A global registration is often insufficient for estimating dendrometric characteristics of trees because individual branches of the same tree may exhibit different positions between two scanning procedures. Therefore, we introduce a localized approach to register point clouds of botanic trees. Given two roughly registered point clouds $ hbox {PC} _ {1} $ and $ hbox {PC} _ {2} $ of a tree, we apply a skeletonization method to both point clouds.

Studies on the great pyramid of King Khufu (2509- 2483 BCE ±25) in Egypt are numerous, but only a few surveys, which are the basis of any hypotheses on the construction of a pyramid, have been conducted. In particular, since no observation of the core of the pyramid has been made, theories about the structure are still hypothetical. In 2013, a Japanese TV production company had the opportunity to climb the northeast corner of the pyramid to shoot a crevice that led to an open space (named “cave”) inside the pyramid, located about 80m from the ground. The authors are fortunate to be allowed to use this video footage for academic research. We employed a “structure from motion” (SfM) technique using Microsoft Photosynth to reconstruct the 3D point cloud of the surface of the cave. Twenty minutes of footage was split into thirty thousand image frames, out of which we selected three hundred images shot using several smooth motions of the camera and used these for the SfM process. SfM tracks the “feature points” in the image sequence to estimate the camera motion and then triangulates these feature points to produce the point clouds. As a result, the static feature points from the overall surface of the cave were effectively collected and reconstructed as point clouds, whereas inconsistent points from a moving person are automatically eliminated through the SfM process. Thus we have produced, albeit in a small area, the first record of the actual structure of the great pyramid’s core. The production of a 3D model from existing video footage is a rather new methodology in the field of archaeology. This set of techniques can be applied to not only academic investigation but also to the restoration and conservation of damaged heritage and artifacts.

""Morphological observations (terrestrial laser scanning) and sediment analysis are used to study beach cusp
morphodynamics at Melbourne Beach (Florida, USA), a moderately sloped beach characterized by fine
sand. The study couples rapid high-resolution surveying with surficial sediment sampling over multiple
tidal cycles. Surveys were run ~500 m alongshore and sediment samples were collected intertidally over a period of 5 days. Beach cusp location within larger scale beach morphology is shown to directly influence
cusp growth as either gross erosional or gross accretional. Sediment characteristics within the beach cusp
morphology are reported coincident with cusp evolution. Variations in particle size distribution kurtosis
are exhibited as the cusps evolve, however no significant correlation is seen between grain size and
position between horn and embayment. During the end of the study, a storm resulted in beach cusp
destruction and increased sediment sorting.""

Holata, L. - Plzák, J. 2013: Products of New Czech Hypsography Based on ALS Technology and Their Potential for Archaeological Research: Evaluation of LIDAR Data and Interpolation to DTMs. In: Neubauer, W. – Trinks, I. – Salisbury, R. B. – Einwögerer, C. (eds.) Archaeological Prospection. Proceedings of the 10th International Conference – Vienna. May 29th – June 2nd 2013. Wien, 372 – 374. 

Holata, L. - Plzák, J. 2013: Examinace procesu optimalizace „archeologicky korektních“ způsobů vyhodnocení dat z leteckého laserového skenování zalesněné krajiny. Potenciál filtrace surových dat, problematika interpolačních algoritmů a způsobů vizualizace antropogenních tvarů v digitálních modelech reliéfu. In: Gojda, M. - John, J. a kol. Archeologie a letecké laserové skenování krajiny. Plzeň, 49-79.