SPARSE POINT CLOUD FILTERING BASED ON COVARIANCE FEATURES

Abstract. This work presents an extended photogrammetric pipeline aimed to improve 3D reconstruction results. Standard photogrammetric pipelines can produce noisy 3D data, especially when images are acquired with various sensors featuring different properties. In this paper, we propose an automatic filtering procedure based on some geometric features computed on the sparse point cloud created within the bundle adjustment phase. Bad 3D tie points and outliers are detected and removed, relying on micro and macro-clusters analyses. Clusters are built according to the prevalent dimensionality class (1D, 2D, 3D) assigned to low-entropy points, and corresponding to the main linear, planar o scatter local behaviour of the point cloud. While the macro-clusters analysis removes smallsized clusters and high-entropy points, in the micro-clusters investigation covariance features are used to verify the inner coherence of each point to the assigned class. Results on heritage scenarios are presented and discussed.</p

Geometric feature analysis for the classification of cultural heritage point clouds

In the last years, the application of artificial intelligence (Machine Learning and Deep Learning methods) for the classification of 3D point clouds has become an important task in modern 3D documentation and modelling applications. The identification of proper geometric and radiometric features becomes fundamental to classify 2D/3D data correctly. While many studies have been conducted in the geospatial field, the cultural heritage sector is still partly unexplored. In this paper we analyse the efficacy of the geometric covariance features as a support for the classification of Cultural Heritage point clouds. To analyse the impact of the different features calculated on spherical neighbourhoods at various radius sizes, we present results obtained on four different heritage case studies using different features configurations

Spectral characterization of a SPDC source with a fast broadband spectrometer

Knowing the properties of the single photons produced in a Spontaneous Parametric Down-Conversion (SPDC) source can be crucial for specific applications and uses. In particular, the spectral properties are of key relevance. Here, we investigate a commercial SPDC source using our fast broadband spectrometer. Our analysis is a valid method for other SPDC sources, as well as other single-photon generation techniques, thus providing a good example of how to use this spectrometer design. We calibrate the spectrometer using known lines of the argon emission spectrum. We show that the two down-converted photons from the SPDC source have different spectral properties depending on the pump power, and in which condition we measured spectrally similar down-converted photons. Lastly, we were able to reconstruct and investigate the spectral information for the pump photon

Incidence of temporomandibular joint clicking in adolescents with and without unilateral posterior cross-bite: a 10-year follow-up study

Among different malocclusions, posterior cross-bite is thought to have a strong impact on the correct functioning of the masticatory system. The association between unilateral posterior cross-bite (UPCB) and temporomandibular joint (TMJ) clicking, however, remains still controversial. The aim of this study was to investigate whether the presence of UCPB during early adolescence increases the risk of reporting TMJ clicking after a long-term follow-up. A longitudinal survey design was carried out in a group of 12-year-old young adolescents, who were examined at baseline for TMJ clicking sounds and unilateral posterior cross-bite. After 10 years, 519 subjects could be reached by a telephone survey. Standardised questions were used to collect self-reported TMJ sounds and to determine whether participants had received an orthodontic treatment. Logistic regression analysis revealed a significant association between unilateral posterior cross-bite and subjectively reported TMJ clicking (odds ratio = 6·0; 95% confidence limits = 3·4-10·8; P < 0·0001). The incidence of TMJ clicking was 12%. At a ten-year follow-up, self-reports of TMJ clicking were significantly associated with the presence of UPCB at baseline, but not with the report of having received an orthodontic treatment. Within the limitation of this study, the presence of unilateral posterior cross-bite in young adolescents may increase the risk of reporting TMJ sounds at a 10-year follow-up. The provision of an orthodontic treatment, however, does not appear to reduce the risk of reporting TMJ sounds

A semi-automated approach to model architectural elements in Scan-to-BIM processes

In the last years, the AEC (Architecture, Engineering and Construction) domain has exponentially increased the use of BIM and HBIM models for several applications, such as planning renovation and restoration, building maintenance, cost managing, or structural/energetic retrofit design. However, obtaining detailed as-built BIM models is a demanding and time-consuming process. Especially in historical contexts, many different and complex architectural elements need to be carefully and manually modelled. Meshes or surfaces and NURBS or polylines, derived from 3D reality-based data, are recently used as a reference for the HBIM accurate modelling. This work proposes a comprehensive and novel semi-automated approach to reconstruct architectural elements through the Visual Programming Language (VPL) Dynamo software and a Boundary-Representation method (B-rep), starting from 3D surveying data and point clouds classification. A wide package of scripts provides solutions for modelling complex shapes and transferring the obtained 3D models into BIM Authoring tools for a complete reconstruction phase. The presented procedure, useful for different BIM or HBIM applications, proved to reduce the modelling time significantly

Web-based randomised controlled trials in orthodontics

Randomised controlled trials (RCT) are considered the best source of scientific evidence--the gold standard--when evaluating the efficacy of orthodontic treatments. Frequently, RCT are planned as multicentre trials, with the intention of increasing statistical power and raising the precision of outcome estimates. The management of large-scale RCT, however, requires even more thorough organisation than conventional RCT. Indeed, the need for high accuracy and standardisation in data collection, research aids, secretarial skills, staff and patient training, and organisational meetings, make these studies time-consuming, expensive and, in general, relatively complex to carry out well. A website was developed to support a large scale-orthodontic RCT which aimed to evaluate the efficacy of a functional appliance(www.ortodonzia.unina.it). Websites such as this can increase the quality of data collection, simplify the randomisation process, speed up data collection, and improve trial monitoring. Web-based RCT have the potential to help globalise orthodontic research and also increase our rate of acquisition of evidence in orthodontics

Indoor/Outdoor Air Quality Assessment at School near the Steel Plant in Taranto (Italy)

This study aims to investigate the air quality in primary school placed in district of Taranto (south of Italy), an area of high environmental risk because of closeness between large industrial complex and urban settlement. The chemical characterization of PM2.5 was performed to identify origin of pollutants detected inside school and the comparison between indoor and outdoor levels of PAHs and metals allowed evaluating intrusion of outdoor pollutants or the existence of specific indoor sources. The results showed that the indoor and outdoor levels of PM2.5, BaP, Cd, Ni, As, and Pb never exceeded the target values issued by World Health Organization (WHO). Nevertheless, high metals and PAHs concentrations were detected especially when school were downwind to the steel plant. TheI/Oratio showed the impact of outdoor pollutants, especially of industrial markers as Fe, Mn, Zn, and Pb, on indoor air quality. This result was confirmed by values of diagnostic ratio as B(a)P/B(g)P, IP/(IP + BgP), BaP/Chry, and BaP/(BaP + Chry), which showed range characteristics of coke and coal combustion. However, Ni and As showedI/Oratio of 2.5 and 1.4, respectively, suggesting the presence of indoor sources

Mediterranean Diet in Developmental Age: A Narrative Review of Current Evidences and Research Gaps

Numerous studies in recent decades have shown that Mediterranean diet (MD) can reduce the risk of developing obesity in pediatric patients. The current narrative review summarizes recent evidence regarding the impact of MD across the different stages of child development, starting from fetal development, analyzing breastfeeding and weaning, through childhood up to adolescence, highlighting the gaps in knowledge for each age group. A literature search covering evidence published between 1 January 2000 and 1 March 2022 and concerning children only was conducted using multiple keywords and standardized terminology in PubMed database. A lack of scientific evidence about MD adherence concerns the age group undergoing weaning, thus between 6 months and one year of life. In the other age groups, adherence to MD and its beneficial effects in terms of obesity prevention has been extensively investigated, however, there are still few studies that correlate this dietary style with the incidence of non-communicable diseases. Furthermore, research on multi-intervention strategy should be implemented, especially regarding the role of education of children and families in taking up this healthy dietary style

QUALITY FEATURES FOR THE INTEGRATION OF TERRESTRIAL AND UAV IMAGES

The paper presents an innovative approach for improving the orientation results when terrestrial and UAV images are jointly processed. With the existing approaches, the processing of images coming from different platforms and sensors leads often to noisy and inaccurate 3D reconstructions, due to the different nature and properties of the acquired images. In this work, a photogrammetric pipeline is proposed to filter and remove bad computed tie points, according to some quality feature indicators. A completely automatic procedure has been developed to filter the sparse point cloud, in order to improve the orientation results before computing the dense point cloud. We report some tests and results on a dataset of about 140 images (Modena cathedral, Italy). The effectiveness of the filtering procedure was verified using some internal quality indicators, external checks (ground truth data) and qualitative visual analyses