Single-tree detection in high-density LiDAR data from UAV-based survey

UAV-based LiDAR survey provides very-high-density point clouds, which involve very rich information about forest detailed structure, allowing for detection of individual trees, as well as demanding high computational load. Single-tree detection is of great interest for forest management and ecology purposes, and the task is relatively well solved for forests made of single or largely dominant species, and trees having a very evident pointed shape in the upper part of the canopy (in particular conifers). Most authors proposed methods based totally or partially on search of local maxima in the canopy, which has poor performance for species that have flat or irregular upper canopy, and for mixed forests, especially where taller trees hide smaller ones. Such considerations apply in particular to Mediterranean hardwood forests. In such context, it is imperative to use the whole volume of the point cloud, however keeping computational load tractable. The authors propose the use of a methodology based on modelling the 3D-shape of the tree, which improves performance w.r.t to maxima-based models. A case study, performed on a hazel grove, is provided to document performance improvement on a relatively simple, but significant, case

Experimenting with New Technologies for Technical Survey in Humanitarian Demining

The Humanitarian Demining Laboratory of Università La Sapienza di Roma, Italy, currently performs research and experimental work for multisensor explosive-remnants-of-war detecting platforms. In this article, the authors report preliminary testing results on a new, active thermal technique discovered through their research

A low-power circuit for piezoelectric vibration control by synchronized switching on voltage sources

In the paper, a vibration damping system powered by harvested energy with implementation of the so-called SSDV (synchronized switch damping on voltage source) technique is designed and investigated. In the semi-passive approach, the piezoelectric element is intermittently switched from open-circuit to specific impedance synchronously with the structural vibration. Due to this switching procedure, a phase difference appears between the strain induced by vibration and the resulting voltage, thus creating energy dissipation. By supplying the energy collected from the piezoelectric materials to the switching circuit, a new low-power device using the SSDV technique is proposed. Compared with the original self-powered SSDI (synchronized switch damping on inductor), such a device can significantly improve its performance of vibration control. Its effectiveness in the single-mode resonant damping of a composite beam is validated by the experimental results.Comment: 11 page

Low‐power global navigation satellite system‐enabled wireless sensor network for acoustic emission localisation in aerospace components

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Preliminary archeological site survey by UAV-borne lidar. A case study

Preliminary analysis of an archaeological site requires the acquisition of information by several diverse diagnostic techniques. Remote sensing plays an important role especially in spatially ex-tended and not easily accessible sites for the purposes of preventive and rescue archaeology, landscape archaeology, and intervention planning. In this paper, we present a case study of a de-tailed topographic survey based on a light detection and ranging (LiDAR) sensor carried by an unmanned aerial vehicle (UAV; also known as drone). The high-resolution digital terrain model, obtained from the cloud of points automatically labeled as ground, was searched exhaustively by an expert operator looking for entrances to prehistoric hypogea. The study documents the useful-ness of such a technique to reveal anthropogenic structures hidden by vegetation and perform fast topographic documentation of the ground surface

UAS FOR ARCHAEOLOGY. NEW PERSPECTIVES ON AERIAL DOCUMENTATION

In this work some Unmanned Aerial Systems applications are discussed and applied to archaeological sites survey and 3D model reconstructions. Interesting results are shown for three important and different aged sites on north Sardinia (Italy). An easy and simplified procedure has proposed permitting the adoption of multi-rotor aircrafts for daily archaeological survey during excavation and documentation, involving state of art in UAS design, flight control systems, high definition sensor cameras and innovative photogrammetric software tools. Very high quality 3D models results are shown and discussed and how they have been simplified the archaeologist work and decisions

Cellular Neural Networks Defined On Log-Polar Grids For Artificial Vision

Use of Cellular Neural Networks is proposed as a tool for artificial vision. Space-variant processing is defined on a foveated sensor space, and optical flow computation studied as a significant case. The study points towards fabrication of integrated circuits containing both sensing and analog preprocessing. I. INTRODUCTION Artificial perception is drawing growing interest with projected application in numerous fields, in particular for robotics and, in the long term, for the design of prosthetic devices. Strict constraints of size, weight, cost and performance must be jointly optimized in these applications, and for this reason, based on inspiration from biology, the concept of space-variant active vision (SVAV) [1] has been developed in the last decade and is now recognized as a very promising approach. SVAV is based on the use of sensors characterized by a smooth variation of resolution across the workspace, like that of the human retina, where pixel dimension is small at the cent..