UAS Flight Path Planning: A Comparative Analysis of Diverse Use Cases and Approaches

Uncrewed aircraft systems (UAS), also known as drones, have become increasingly popular in various applications due to their ability to access remote or challenging locations. A crucial aspect of UAS operations is flight path planning, which determines the trajectory the aircraft takes to achieve its mission objectives. However, the diverse use cases of UAS demand different planning approaches tailored to their specific requirements. This paper presents an overview over current research in UAS flight path planning and proposes a categorization of use cases based on their distinct goals and considerations. The terminology differentiates the goals of tasks between navigation-centric and data acquisition and also considers their context, domain, perspective, and sensors. We analyze existing approaches with a focus on UAS flight path planning for data acquisition using cameras, highlighting their strengths and limitations. This structured overview facilitates the understanding of the diverse landscape of UAS flight path planning and paves the way for the development of more targeted and effective solutions for various applications and their use cases. The analysis shows, that the term ”UAS flight path planning” is currently used in a variety of distinct use cases with diverging requirements, so a unified terminology should be established for clear communication

Correspondência eficiente de descritores SIFT para construção de mapas densos de pontos homólogos em imagens de sensoriamento remoto

Métodos automáticos de localização de pontos homólogos em imagens digitais baseados em área, combinados com técnicas de crescimento de região, são capazes de produzir uma malha densa e exata de pontos homólogos. Entretanto, o processo de crescimento de região pode ser interrompido em regiões da imagem, cuja paralaxe no eixo horizontal apresenta variação abrupta. Essa situação geralmente é causada por uma descontinuidade na superfície ou espaço-objeto imageado, tal como um prédio numa cena urbana ou um paredão de exploração de uma mina a céu aberto. Nesses casos, novos pares de pontos homólogos (sementes) devem ser introduzidos, normalmente por um operador humano, a partir dos quais o processo é reiniciado. Dependendo do tipo da imagem utilizada e da estrutura 3D da região mapeada, a intervenção humana pode ser considerável. Uma alternativa totalmente automatizada em que se combinam as técnicas SIFT (Scale Invariant Feature Transform), pareamento por mínimos quadrados e crescimento de região foi proposta anteriormente pelos autores. O presente trabalho apresenta uma extensão a essa técnica. Basicamente, propõem-se alterações na etapa de correspondência do SIFT, que exploram características de estereogramas produzidos por sensores aéreos e orbitais. Avaliações experimentais demonstram que as modificações propostas trazem dois tipos de benefícios. Em primeiro lugar, obtém-se um aumento do número de pontos homólogos encontrados, sem aumento correspondente na proporção de falsas correspondências. Em segundo lugar, a carga computacional é reduzida substancialmente

ENHANCEMENT STRATEGIES FOR FRAME-TO-FRAME UAS STEREO VISUAL ODOMETRY

Autonomous navigation of indoor unmanned aircraft systems (UAS) requires accurate pose estimations usually obtained from indirect measurements. Navigation based on inertial measurement units (IMU) is known to be affected by high drift rates. The incorporation of cameras provides complementary information due to the different underlying measurement principle. The scale ambiguity problem for monocular cameras is avoided when a light-weight stereo camera setup is used. However, also frame-to-frame stereo visual odometry (VO) approaches are known to accumulate pose estimation errors over time. Several valuable real-time capable techniques for outlier detection and drift reduction in frame-to-frame VO, for example robust relative orientation estimation using random sample consensus (RANSAC) and bundle adjustment, are available. This study addresses the problem of choosing appropriate VO components. We propose a frame-to-frame stereo VO method based on carefully selected components and parameters. This method is evaluated regarding the impact and value of different outlier detection and drift-reduction strategies, for example keyframe selection and sparse bundle adjustment (SBA), using reference benchmark data as well as own real stereo data. The experimental results demonstrate that our VO method is able to estimate quite accurate trajectories. Feature bucketing and keyframe selection are simple but effective strategies which further improve the VO results. Furthermore, introducing the stereo baseline constraint in pose graph optimization (PGO) leads to significant improvements

COMPARISON AND EVALUATION OF FEATURE POINT DETECTORS

Low-level feature extraction is the first step in any image analysis procedure and is essential for the performance of stereo vision and object recognition systems. Research concerning the detection of corners, blobs and circular or point like features is particularly rich and many procedures have been proposed in the literature. In this paper, several frequently used methods and some novel ideas are tested and compared. We measure the performance of the detectors under the criteria of their detection and repeatability rate as well as the localization accuracy. We present a short review of the major interest point detectors, propose some improvements and describe the experimental setup used for our comparison. Finally, we determine which detector leads to the best results and show that it satisfies the criteria specified above. 1

Probabilistic and Biologically Inspired Feature Representations

Under the title "Probabilistic and Biologically Inspired Feature Representations," this text collects a substantial amount of work on the topic of channel representations. Channel representations are a biologically motivated, wavelet-like approach to visual feature descriptors: they are local and compact, they form a computational framework, and the represented information can be reconstructed. The first property is shared with many histogram- and signature-based descriptors, the latter property with the related concept of population codes. In their unique combination of properties, channel representations become a visual Swiss army knife—they can be used for image enhancement, visual object tracking, as 2D and 3D descriptors, and for pose estimation. In the chapters of this text, the framework of channel representations will be introduced and its attributes will be elaborated, as well as further insight into its probabilistic modeling and algorithmic implementation will be given. Channel representations are a useful toolbox to represent visual information for machine learning, as they establish a generic way to compute popular descriptors such as HOG, SIFT, and SHOT. Even in an age of deep learning, they provide a good compromise between hand-designed descriptors and a-priori structureless feature spaces as seen in the layers of deep networks.EMC2, WASP, ELLIIT, CENTAURO, SymbiCloud, CYCL

Sound velocities of skiagite–iron–majorite solid solution to 56 GPa probed by nuclear inelastic scattering

High-pressure experimental data on sound velocities of garnets are used for interpretation of seismological data related to the Earth’s upper mantle and the mantle transition zone. We have carried out a Nuclear Inelastic Scattering study of iron-silicate garnet with skiagite (77 mol%)–iron–majorite composition in a diamond anvil cell up to 56 GPa at room temperature. The determined sound velocities are considerably lower than sound velocities of a number of silicate garnet end-members, such as grossular, pyrope, Mg–majorite, andradite, and almandine. The obtained sound velocities have the following pressure dependencies: $V_p$ [km/s] = 7.43(9) + 0.039(4) × P [GPa] and $V_s$ [km/s] = 3.56(12) + 0.012(6) × P [GPa]. We estimated sound velocities of pure skiagite and khoharite, and conclude that the presence of the iron–majorite component in skiagite strongly decreases $V_s$ . We analysed the influence of Fe$^{3+}$ on sound velocities of garnet solid solution relevant to the mantle transition zone and consider that it may reduce sound velocities up to 1% relative to compositions with only Fe$^{2+}$ in the cubic site

Experimental bond critical point and local energy density properties determined for Mn-O, Fe-O, and Co-O bonded interactions for tephroite, Mn2SiO4Mn_2SiO_4, fayalite, Fe2SiO4Fe_2SiO_4, and Co2SiO4Co_2SiO_4 olivine and selected organic metal complexes

Bond critical point (bcp) and local energy density properties for the electron density (ED) distributions, calculated with first-principle quantum mechanical methods for divalent transition metal Mn-, Co-, and Fe-containing silicates and oxides are compared with experimental model ED properties for tephroite, Mn 2SiO 4, fayalite, Fe 2SiO 4, and Co 2SiO 4 olivine, each determined with high-energy synchrotron single-crystal X-ray diffraction data. Trends between the experimental bond lengths, R(M-O), (M = Mn, Fe, Co), and the calculated bcp properties are comparable with those observed for non-transition M-O bonded interactions. The bcp properties, local total energy density, H( r c), and bond length trends determined for the Mn-O, Co-O, and Fe-O interactions are also comparable. A comparison is also made with model experimental bcp properties determined for several Mn-O, Fe-O, and Co-O bonded interactions for selected organometallic complexes and several oxides. Despite the complexities of the structures of the organometallic complexes, the agreement between the calculated and model experimental bcp properties is fair to good in several cases. The G( r c)/rho( r c) versus R(M-O) trends established for non-transition metal M-O bonded interactions hold for the transition metal M-O bonded interactions with G( r c)/rho( r c) increasing in value as H( r c) becomes progressively more negative in value, indicating an increasing shared character of the interaction as G( r c)/rho( r c) increases in value. As observed for the non-transition metal M-O bonded interactions, the Laplacian, nabla (2)rho( r c), increases in value as rho( r c) increases and as H( r c) decreases and becomes progressive more negative in value. The Mn-O, Fe-O, and Co-O bonded interactions are indicated to be of intermediate character with a substantial component of closed-shell character compared with Fe-S and Ni-S bonded interactions, which show greater shared character based on the | V( r c)|/ G( r c) bond character indicator. The atomic charges conferred on the transition metal atoms for the three olivines decrease with increasing atomic number from Mn to Fe to Co as the average M-O bond lengths decrease from 2.219 to 2.168 to 2.128 A, respectively

Carbon Fluxes and Primary Magma CO2 Contents Along the Global Mid‐Ocean Ridge System

International audienceThe concentration of carbon in primary mid-ocean ridge basalts (MORBs), and the associated fluxes of CO2 outgassed at ocean ridges, is examined through new data obtained by secondary ion mass spectrometry (SIMS) on 753 globally distributed MORB glasses. MORB glasses are typically 80–90% degassed of CO2. We thus use the limited range in CO2/Ba (81.3 ± 23) and CO2/Rb (991 ± 129), derived from undegassed MORB and MORB melt inclusions, to estimate primary CO2 concentrations for ridges that have Ba and/or Rb data. When combined with quality-controlled volatile-element data from the literature (n = 2,446), these data constrain a range of primary CO2 abundances that vary from 104 ppm to 1.90 wt%. Segment-scale data reveal a range in MORB magma flux varying by a factor of 440 (from 6.8 × 105 to 3.0 × 108 m3/year) and an integrated global MORB magma flux of 16.5 ± 1.6 km3/year. When combined with CO2/Ba and CO2/Rb-derived primary magma CO2 abundances, the calculated segment-scale CO2 fluxes vary by more than 3 orders of magnitude (3.3 × 107 to 4.0 × 1010 mol/year) and sum to an integrated global MORB CO2 flux of urn:x-wiley:15252027:media:ggge21753:ggge21753-math-0001 × 1012 mol/year. Variations in ridge CO2 fluxes have a muted effect on global climate; however, because the vast majority of CO2 degassed at ridges is dissolved into seawater and enters the marine bicarbonate cycle. MORB degassing would thus only contribute to long-term variations in climate via degassing directly into the atmosphere in shallow-water areas or where the ridge system is exposed above sea level