SurfelMeshing: Online Surfel-Based Mesh Reconstruction

We address the problem of mesh reconstruction from live RGB-D video, assuming a calibrated camera and poses provided externally (e.g., by a SLAM system). In contrast to most existing approaches, we do not fuse depth measurements in a volume but in a dense surfel cloud. We asynchronously (re)triangulate the smoothed surfels to reconstruct a surface mesh. This novel approach enables to maintain a dense surface representation of the scene during SLAM which can quickly adapt to loop closures. This is possible by deforming the surfel cloud and asynchronously remeshing the surface where necessary. The surfel-based representation also naturally supports strongly varying scan resolution. In particular, it reconstructs colors at the input camera's resolution. Moreover, in contrast to many volumetric approaches, ours can reconstruct thin objects since objects do not need to enclose a volume. We demonstrate our approach in a number of experiments, showing that it produces reconstructions that are competitive with the state-of-the-art, and we discuss its advantages and limitations. The algorithm (excluding loop closure functionality) is available as open source at https://github.com/puzzlepaint/surfelmeshing .Comment: Version accepted to IEEE Transactions on Pattern Analysis and Machine Intelligenc

Syntactic vs. Semantic Locality: How Good Is a Cheap Approximation?

Extracting a subset of a given OWL ontology that captures all the ontology's knowledge about a specified set of terms is a well-understood task. This task can be based, for instance, on locality-based modules (LBMs). These come in two flavours, syntactic and semantic, and a syntactic LBM is known to contain the corresponding semantic LBM. For syntactic LBMs, polynomial extraction algorithms are known, implemented in the OWL API, and being used. In contrast, extracting semantic LBMs involves reasoning, which is intractable for OWL 2 DL, and these algorithms had not been implemented yet for expressive ontology languages. We present the first implementation of semantic LBMs and report on experiments that compare them with syntactic LBMs extracted from real-life ontologies. Our study reveals whether semantic LBMs are worth the additional extraction effort, compared with syntactic LBMs

Why Having 10,000 Parameters in Your Camera Model is Better Than Twelve

Camera calibration is an essential first step in setting up 3D Computer Vision systems. Commonly used parametric camera models are limited to a few degrees of freedom and thus often do not optimally fit to complex real lens distortion. In contrast, generic camera models allow for very accurate calibration due to their flexibility. Despite this, they have seen little use in practice. In this paper, we argue that this should change. We propose a calibration pipeline for generic models that is fully automated, easy to use, and can act as a drop-in replacement for parametric calibration, with a focus on accuracy. We compare our results to parametric calibrations. Considering stereo depth estimation and camera pose estimation as examples, we show that the calibration error acts as a bias on the results. We thus argue that in contrast to current common practice, generic models should be preferred over parametric ones whenever possible. To facilitate this, we released our calibration pipeline at https://github.com/puzzlepaint/camera_calibration, making both easy-to-use and accurate camera calibration available to everyone.Comment: 15 pages, 12 figures, accepted to CVPR 2020 as an ora

How to Improve Accessibility of Natural Areas: About the Relevance of Providing Information on Accessible Services and Facilities in Natural Areas

Accessibility is a topic of increasing importance concerning all fields of life. This is underlined by current legislation as well as social meaning and economic benefits related to accessibility. Due to recent demographic changes in society characterised by steadily growing numbers of the elderly (with age-related physical deficits), enabling people with disabilities to manage their everyday independently gets even more important. However, in order to fully participate in life self-determined, the disabled demand for barrier free infrastructure in many ways. This is particularly true in terms of tourist and recreational activities in natural areas. At that, positive effects of being in nature (e.g. on people’s physical health and mental well-being as well as integration and family solidarity) are even more relevant for disabled people than for others. While many efforts exist on offering and improving barrier free services and facilities on-site, it seems that there is a lack of off-site material informing persons with disabilities of accessible services and facilities available in natural areas. That is surprising, since today, rapid advances in information and communication technologies offer many ways to provide digital, i.e. web-based solution suitable to impart all kinds of information and to meet the needs of disabled people. Concerning the spatial reference of nature-based recreation, i.e. in order to communicate location and spatial relationship of services and facilities, web-based maps are a central means of communication. But, which information regarding tourist and recreational visits of natural areas is required by disabled visitors? How to present this information to the target group in an accessible and useful way? How to design and integrate web-based maps as powerful tool to impart spatial information? Based on research conducted within the project “senTOUR”, this paper aims to offer suggestions for proving accessible digital information in order to support recreational and tourist activities in natural areas for disabled visitors, i.e. for the elderly who often suffer from age-related physical deficits

Development of an Instrument to Measure Handball Ability of Beginning Level Players in a Physical Education Class

Higher Educatio

Spatial heterogeneity in temporal dynamics of Alpine bird communities along an elevational gradient

Aim: Mountains are biodiversity hotspots and are among the most sensitive ecosystems to ongoing global change being thus of conservation concern. Under this scenario, assessing how biological communities vary over time along elevational gradients and the relative effects of niche-based deterministic processes and stochastic events in structuring assemblages is essential. Here, we examined how the temporal trends of bird communities vary with elevation over a 20 year-period (1999-2018). We also tested for differences in temporal dynamics among habitat types (among-community variability) and functional groups (within-community variability). Taxon: 97 species of common breeding birds. Location: Swiss Alps. Methods: We used abundance data from the Swiss breeding bird survey to compute different temporal dynamics metrics (temporal turnover, synchrony, rate of community change, and community-level of covariance among species). We also examined the relative contribution of deterministic and stochastic processes in community assembly using the Raup-Crick method and the normalized stochasticity ratio. Results: We found that, with greater elevation, temporal species turnover increased while the rate of overall community change over successive years decreased, suggesting that high-elevation communities display more erratic dynamics with no clear trend. Despite this, we found a more deterministic assembly of alpine communities in comparison to those located at lower elevations. Deterministic processes had greater influence than stochastic processes on community assembly along the entire elevational gradient (80% of communities). Forest communities exhibited higher synchrony in comparison to the remaining habitats likely because they consisted of species with greater functional redundancy, whereas alpine communities were the least stable as a result of their low taxonomic richness (‘portfolio’ effect). Main conclusions: Community-level synchrony was overall positive supporting the idea that compensatory mechanisms are rare in natural biological communities. Our results suggest that rather than competition, the existence of differences in the ecological strategies of species may have a stabilizing effect on bird communities by weakening the concordance of species responses to fluctuations in environmental conditions (i.e., enhanced interspecific temporal asynchrony). This study provides evidence that, although species turnover in metacommunities is frequent, a high temporal turnover does not necessarily imply the overriding importance of stochastic processes.info:eu-repo/semantics/acceptedVersio

Temporal homogenization of functional and beta diversity in bird communities of the Swiss Alps

Aim Describing the spatio‐temporal dynamics of biotic communities is critical for understanding how environmental change can affect biodiversity. Mountains are especially susceptible to such changes (e.g., climate change) and, consequently, have been identified as ecosystems of conservation concern. With their sharp physical and ecological transitions, altitudinal gradients allow examining the influence of different climatic conditions and land use types on species assemblages across small spatial extents, and thus, they constitute natural laboratories to study diversity–environment relationships. Location Switzerland. Methods We take advantage of long‐term (20 years) monitoring data and an extensive trait dataset (100 traits) to examine spatial patterns, temporal trends, and spatio‐temporal dynamics in functional and beta diversity of bird communities in the Swiss Alps. Results Functional diversity indices showed a congruent pattern over time and across space; most indices decreased over the study period and were strongly correlated with altitude. In agreement with studies from the tropics, we found that communities in the lowlands were functionally over‐dispersed, whereas communities at higher elevations were functionally clustered. High‐altitude communities exhibited high functional originality, low levels of niche differentiation and a high turnover rate. Beta diversity declined over the study period. Conclusions Our findings suggest that pastoral abandonment does not result in an increase in avian functional diversity as most species colonizing woody‐encroached grasslands are functionally redundant, whereas alpine meadows are inhabited by species exhibiting a high degree of habitat specialization and unique functional traits. Hence, the tree line constitutes a boundary between two well‐differentiated functional groups: one representing a functional continuum from lowlands dominated by agricultural landscape to high‐mountain forests, and the other one composed of alpine communities. Overall, this study reveals a process of biotic homogenization (i.e., increasing functional similarity) across the last two decades in the Swiss Alps, coinciding with the recently reported increases in the abundance of generalist species

Gesundheitsentwicklung in Deutschland bis 2037: Eine volkswirtschaftliche Kostensimulation

Die Studie zeigt, wie sich die direkten Kosten, das heißt die Kosten, die für die Behandlung von Krankheiten aufgewendet werden müssen und die indirekten Krankheitskosten, das heißt die Kosten durch den krankheitsbedingten Arbeitsausfall von Erwerbstätigen, aufgrund der Demografie verändern werden und welche Kostensenkungen dabei eine verbesserte Gesundheit bewirken kann. Dabei wurden zwei Simulationen durchgeführt, die jeweils auf einer Bevölkerungsprognose des Statistischen Bundesamtes beruhen