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Classification of Urban Hyperspectral Remote Sensing Imagery Based on Optimized Spectral Angle Mapping
摘要： Hyperspectral remote sensing imagery provides highly precise spectral information. Thus, it is suitable for the land use classification of urban areas that are composed of complicated structures. In this study, a new spectral angle and vector mapping (SAVM) classification method, which adds a factor based on ''the differences in the spectral vector lengths'' among image pixels to the spectral angle mapping (SAM) classification method, is proposed. The SAM and SAVM methods were applied to classify the aerial hyperspectral digital imagery collection experiment imagery acquired from the business district of Washington, DC, USA. The results demonstrated that the overall classification accuracy of the SAM was 64.29%, with a Kappa coefficient of 0.57, while the overall classification accuracy of the SAVM was 81.06%, with a Kappa coefficient of 0.76. The overall classification accuracy was improved by 16.77% by the SAVM, indicating that the use of a SAVM classification method that considers both the spectral angle between the reference spectrum and the test spectrum and the differences in the spectral vector lengths among image pixels can improve the classification accuracy of urban area with hyperspectral remote sensing imagery.
关键词： Hyperspectral imagery,Spectral angle and vector mapping (SAVM),Classification,Spectral angle mapping (SAM)
更新于2025-09-23 15:23:52
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Deep multispectral painting reproduction via multi-layer, custom-ink printing
摘要： We propose a workflow for spectral reproduction of paintings, which captures a painting's spectral color, invariant to illumination, and reproduces it using multi-material 3D printing. We take advantage of the current 3D printers' capabilities of combining highly concentrated inks with a large number of layers, to expand the spectral gamut of a set of inks. We use a data-driven method to both predict the spectrum of a printed ink stack and optimize for the stack layout that best matches a target spectrum. This bidirectional mapping is modeled using a pair of neural networks, which are optimized through a problem-specific multi-objective loss function. Our loss function helps find the best possible ink layout resulting in the balance between spectral reproduction and colorimetric accuracy under a multitude of illuminants. In addition, we introduce a novel spectral vector error diffusion algorithm based on combining color contoning and halftoning, which simultaneously solves the layout discretization and color quantization problems, accurately and efficiently. Our workflow outperforms the state-of-the-art models for spectral prediction and layout optimization. We demonstrate reproduction of a number of real paintings and historically important pigments using our prototype implementation that uses 10 custom inks with varying spectra and a resin-based 3D printer.
关键词： spectral reproduction,3d printing,multi-spectral imaging
更新于2025-09-23 15:23:52
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Radiative energy and exergy analyses of spectrally-selective surfaces for CSP systems
摘要： This work presents a new methodology for calculations of spectral radiative energy and radiative exergy to evaluate the performances of concentrated solar power (CSP) systems. Spectral radiative properties and the operating temperature of selective surfaces, along with the temperature of the environment, are taken into account in analyses. The fundamental expressions needed for the spectral radiative energy and exergy analyses are introduced first. Then, the two approaches are used to assess the spectral performance of five selective coatings. The spectral analysis is performed in the wavelength range of 250 nm to 20,000 nm, while thermal analysis is carried out for the temperature range of 325 K to 800 K. NREL 6A coating was found to result in the highest radiative energy and radiative exergy for both efficiencies and gains, and for the best thermal stability compared to the other coatings.
关键词： selective coating,spectral radiative energy analysis,concentrating solar power systems,spectral radiative exergy analysis
更新于2025-09-23 15:23:52
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An Interplay between Photons, Canopy Structure, and Recollision Probability: A Review of the Spectral Invariants Theory of 3D Canopy Radiative Transfer Processes
摘要： Earth observations collected by remote sensors provide unique information to our ever-growing knowledge of the terrestrial biosphere. Yet, retrieving information from remote sensing data requires sophisticated processing and demands a better understanding of the underlying physics. This paper reviews research efforts that lead to the developments of the stochastic radiative transfer equation (RTE) and the spectral invariants theory. The former simplifies the characteristics of canopy structures with a pair-correlation function so that the 3D information can be succinctly packed into a 1D equation. The latter indicates that the interactions between photons and canopy elements converge to certain invariant patterns quantifiable by a few wavelength independent parameters, which satisfy the law of energy conservation. By revealing the connections between plant structural characteristics and photon recollision probability, these developments significantly advance our understanding of the transportation of radiation within vegetation canopies. They enable a novel physically-based algorithm to simulate the 'hot-spot' phenomenon of canopy bidirectional reflectance while conserving energy, a challenge known to the classic radiative transfer models. Therefore, these theoretical developments have a far-reaching influence in optical remote sensing of the biosphere.
关键词： vegetation remote sensing,stochastic radiative transfer equation,spectral invariants theory
更新于2025-09-23 15:23:52
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Spectral correction for handheld optoacoustic imaging by means of near-infrared optical tomography in reflection mode
摘要： In vivo imaging of tissue/vasculature oxygen saturation levels is of prime interest in many clinical applications. To this end, the feasibility of combining two distinct and complementary imaging modalities was investigated: optoacoustics (OA) and near-infrared tomography (NIROT), both operating noninvasively in reflection mode. Experiments were conducted on two optically heterogeneous phantoms mimicking tissue before and after the occurrence of a perturbation. OA imaging was used to resolve submillimetric vessel-like optical absorbers at depths up to 25 mm, but with a spectral distortion in the OA signals. NIROT measurements were utilized to image perturbations in the background and to estimate the light fluence inside the phantoms at the wavelength pair (760 nm, 830 nm). This enabled the spectral correction of the vessel-like absorbers' OA signals: the error in the ratio of the absorption coefficient at 830 nm to that at 760 nm was reduced from 60%-150% to 10%-20%. The results suggest that oxygen saturation (SO2) levels in arteries can be determined with <10% error and furthermore, that relative changes in vessels' SO2 can be monitored with even better accuracy. The outcome relies on a proper identification of the OA signals emanating from the studied vessels.
关键词： fluence compensation,near-infrared optical tomography,blood oxygen saturation,quantitative optoacoustic imaging,optoacoustic signal quantification,multimodal imaging,spectral correction
更新于2025-09-23 15:23:52
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Performance Limits of FSO Based SAC-OCDMA System Under Weather Conditions
摘要： In this paper, the Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) is investigated in Free Space Optics (FSO) using Zero Cross Correlation (ZCC) codes to evaluate its performance limits in terms of link range. The system is analyzed under clear, haze, moderate fog and dense fog weather conditions. This system has been evaluated numerically and by simulation analysis by maintaining the transmitted power at 10 dBm, for safety reason, according to International Telecommunication Union (ITU) and minimum acceptable BER of 10–9. The simulation results shown that the present system can transmit 622 Mbps/1 Gbps up to maximum link range of 1450 m/1100 m and 61 m/54 m under clear and dense fog conditions, respectively.
关键词： fog,haze,free space optic (FSO),spectral amplitude coding optical code division multiple access (SAC-OCDMA),zero cross-correlation (ZCC)
更新于2025-09-23 15:23:52
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[IEEE 2018 3rd International Conference on Computer Science and Engineering (UBMK) - Sarajevo, Bosnia and Herzegovina (2018.9.20-2018.9.23)] 2018 3rd International Conference on Computer Science and Engineering (UBMK) - Hyperspectral Image Classification Using Reduced Extreme Learning Machine
摘要： In the classification of hyperspectral images, kernel based approaches have been shown to be successful results. Too much training or testing data in the images increases the computation time and memory requirements in the kernel computations. Extreme learning machines that can be used with the kernel approach also need the same requirements in kernel computations. In this study, improvements were made in terms of computation time and memory using reduced kernel extreme learning machines (RKELM). The obtained results are presented comparatively through the tables of performance and time information with kernel extreme learning machine (KELM).
关键词： classification,spectral information,Hyperspectral images,reduced kernel extreme learning machine
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Using Reflectance Spectroscopy to Characterize Surface Landforms and Volcanic Deposits on Deception Island (Antarctica)
摘要： Deception Island is an active volcano in the Antarctic Peninsula region, affected by different geomorphological processes interacting to form a complex mosaic of landforms and deposits. The use of visible near infrared reflectance is an ideal tool for characterizing and monitoring surface covers and substrates. The objective of this work was to use reflectance spectroscopy to identify spectral characteristics of surface covers related to different volcanic deposits in ice-free areas of Deception Island, South-Shetland Islands. A site specific spectral library containing 220 reference spectra was compiled. Image-derived spectra from multispectral satellite data were easily labeled using the reference spectra. A preliminary distribution has distinguished five different deposit types over the entire area of Deception Island.
关键词： Reflectance spectra,spectral library,volcanic deposits,multispectral,geomorphology,South Shetland Islands
更新于2025-09-23 15:23:52
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Microvascular Capillary Plexus Findings of Commotio Retinae on Optical Coherence Tomography Angiography
摘要： Optical coherence tomography (OCT) and histopathology features of commotio retinae (CR) have been established, but alterations of the microvascular macular capillary plexus on OCT angiography (OCTA) has not been previously studied. We present a 46-year-old man who sustained a tennis ball injury to the right eye with visual acuity reduction to 20/30 and grey-white deep macular discoloration, suggestive of CR. Spectral-domain OCT (SD-OCT) showed increased reflectivity and thickness of the ellipsoid zone (junction of photoreceptor inner and outer segments). OCTA revealed no apparent microvascular alterations (right versus left eye) in the foveal avascular zone superficial (0.42 vs. 0.43 mm2) and deep (0.45 vs. 0.44 mm2), superficial foveal capillary density (34.1 vs. 32.6%), and superficial parafoveal capillary density (55.2 vs. 52.2%). Deep macular capillary plexus and choriocapillaris were qualitatively comparable between the two eyes. At 2 months’ follow-up, SD-OCT had normalized. CR is characterized by disruption of the ellipsoid zone without detectable alteration of the capillary plexuses.
关键词： Optical coherence tomography angiography,Commotio retinae,Berlin’s edema,Spectral-domain optical coherence tomography,Traumatic maculopathy
更新于2025-09-23 15:23:52
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Correlations among lighting quality metrics for interior lighting
摘要： Correlations between selected lighting quality metrics derived from the spectrum were computed and interpreted for a representative set of interior light source spectra. Metrics of brightness and the melanopic effect were strongly correlated with each other but not with the metrics of colour quality. Results can be used to establish a two-dimensional diagram with criterion values to ensure the general user acceptance of a lighting system. This diagram can be extended in the future by further metrics describing light intensity and spatial and temporal distributions. Relationships between lighting quality metrics and colorimetric quantities as well as photoreceptor signal values are also shown.
关键词： lighting quality metrics,spectral design,correlations,human-centric lighting,interior lighting
更新于2025-09-23 15:23:52