34 results for "Christopher Small"
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Spectrometry of the Urban Lightscape
NASA’s Gateway to Astronaut Photography of Earth contains over 30,000 photos of ~2500 cataloged urban lightscapes (anthropogenic night light) taken from the International Space Station. A subset of over 100 of these multispectral DSLR photos are of sufficient spatial resolution, sharpness and…
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Spatiotemporal Characterization of VIIRS Night Light
The Visible Infrared Imaging Radiometer Suite (VIIRS) Day Night Band (DNB) on board the Suomi NPP satellite now provides almost a decade of daily observations of night light. The temporal frequency of sampling, without the degree of temporal averaging of annual composites, makes it necessary to…
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Multisensor Characterization of Urban Morphology and Network Structure
The combination of decameter resolution Sentinel 2 and hectometer resolution VIIRS offers the potential to quantify urban morphology at scales spanning the range from individual objects to global scale settlement networks. Multi-season spectral characteristics of built environments provide an…
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A Continuous Cryosphere Index for Snow and Ice Reflectance
…all studies of snow and ice spectroscopy have been limited to single or small numbers of specific cryospheric environments. These studies serve a diversity of objectives, but together also suggest the importance of the global continuum of snow and ice composition and spectroscopy. The continuum of…
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Spatiotemporal Characterization of Mangrove Phenology and Disturbance Response: The Bangladesh Sundarban
This work presents a spatiotemporal analysis of the phenology and disturbance response in the Sundarban mangrove forest on the Ganges-Brahmaputra Delta in Bangladesh. The methodological approach is based on an Empirical Orthogonal Function (EOF) analysis of the new Harmonized Landsat Sentinel-2…
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Mapping and Monitoring Rice Agriculture with Multisensor Temporal Mixture Models
Rice is the staple food for more than half of humanity. Accurate prediction of rice harvests is therefore of considerable global importance for food security and economic stability, especially in the developing world. Landsat sensors have collected coincident thermal and optical images for the past…
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Spectroscopic Characterization of Built Environments in China
Spectral mixing space characterization is especially important for studies of built environments because of the range of materials around which humans establish residence. With the launch of NASA’s EMIT imaging spectrometer in 2022, spectroscopic characterization of a variety of built environments…
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Spectral Characteristics of the Dynamic World Land Cover Classification
The Dynamic World product is a discrete land cover classification of Sentinel 2 reflectance imagery that is global in extent, retrospective to 2015, and updated continuously in near real time. The classifier is trained on a stratified random sample of 20,000 hand-labeled 5 × 5 km Sentinel 2 tiles…
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Topological Generality and Spectral Dimensionality in the Earth Mineral Dust Source Investigation (EMIT) Using Joint Characterization and the Spectral Mixture Residual
NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) mission seeks to use spaceborne imaging spectroscopy (hyperspectral imaging) to map the mineralogy of arid dust source regions. Here we apply recent developments in Joint Characterization (JC) and the spectral Mixture Residual (MR) to…
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Which Vegetation Index? Benchmarking Multispectral Metrics to Hyperspectral Mixture Models in Diverse Cropland
The monitoring of agronomic parameters like biomass, water stress, and plant health can benefit from synergistic use of all available remotely sensed information. Multispectral imagery has been used for this purpose for decades, largely with vegetation indices (VIs). Many multispectral VIs exist…
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Joint Characterization of Sentinel-2 Reflectance: Insights from Manifold Learning
Most applications of multispectral imaging are explicitly or implicitly dependent on the dimensionality and topology of the spectral mixing space. Mixing space characterization refers to the identification of salient properties of the set of pixel reflectance spectra comprising an image (or…
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Land Cover Dynamics on the Lower Ganges–Brahmaputra Delta: Agriculture–Aquaculture Transitions, 1972–2017
Aquaculture in tropical and subtropical developing countries has expanded in recent years. This practice is controversial due to its potential for serious economic, food security, and environmental impacts—especially for intensive operations in and near mangrove ecosystems, where many shrimp…
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Spectral Mixture Analysis as a Unified Framework for the Remote Sensing of Evapotranspiration
This study illustrates a unified, physically-based framework for mapping landscape parameters of evapotranspiration (ET) using spectral mixture analysis (SMA). The framework integrates two widely used approaches by relating radiometric surface temperature to subpixel fractions of substrate (S)…
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Multisensor Analysis of Spectral Dimensionality and Soil Diversity in the Great Central Valley of California
…structure of the global feature space is present in our relatively small spatial subset of California. Finally, we find that the multispectral dataset well represents the substrate EM variability present in the study area – despite its inability to resolve narrow band absorptions. We observe a…
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Joint Characterization of the Cryospheric Spectral Feature Space
Multispectral and hyperspectral feature spaces are useful for a variety of remote sensing applications ranging from spectral mixture modeling to discrete thematic classification. In many of these applications, models are used to project the higher dimensional continuum of reflectances (or…
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Joint Characterization of Spatiotemporal Data Manifolds
Modeling spatiotemporal data can be a challenge due to the plethora of processes, both independent and interacting, which may or may not contribute to the measurements. Characterization can be considered a complement to modeling by helping guide assumptions about generative processes and their…
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Spatiotemporal evolution of COVID-19 infection and detection within night light networks: comparative analysis of USA and China
…with an abrupt transition from slow increases in confirmed cases in a small number of network components in January and February, to rapid geographic dispersion to a larger number of components shortly before mobility reductions occurred in March. Results indicate that while most of the upper tail…
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Multiscale topology of the spectroscopic mixing space: crystalline substrates
The statistical and topological properties of spectral feature spaces are direct expressions of the populations of spectra they represent. Characterization of the topology and dimensionality of spectral feature spaces provides both quantitative and qualitative insight into their information…
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The Standardized Spectroscopic Mixture Model
…beyond [0, 1]. However, a refined spectroscopic SVD model still achieves small (
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The Sentinel 2 MSI Spectral Mixing Space
A composite spectral feature space is used to characterize the spectral mixing properties of Sentinel 2 Multispectral Instrument (MSI) spectra over a wide diversity of landscapes. Characterizing the linearity of spectral mixing and identifying bounding spectral endmembers allows the Substrate…