The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Huanfeng Shen - One of the best experts on this subject based on the ideXlab platform.
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Spatial–Spectral Fusion in Different Swath Widths by a Recurrent Expanding Residual Convolutional Neural Network
Remote Sensing, 2019Co-Authors: Qiangqiang Yuan, Huanfeng ShenAbstract:The quality of remotely sensed images is usually determined by their spatial resolution, spectral resolution, and coverage. However, due to limitations in the sensor hardware, the spectral resolution, spatial resolution, and Swath Width of the coverage are mutually constrained. Remote sensing image fusion aims at overcoming the different constraints of remote sensing images, to achieve the purpose of combining the useful information in the different images. However, the traditional spatial–spectral fusion approach is to use data in the same Swath Width that covers the same area and only considers the mutually constrained conditions between the spectral resolution and spatial resolution. To simultaneously solve the image fusion problems of the Swath Width, spatial resolution, and spectral resolution, this paper introduces a method with multi-scale feature extraction and residual learning with recurrent expanding. To discuss the sensitivity of convolution operation to different variables of images in different Swath Widths, we set the sensitivity experiments in the coverage ratio and offset position. We also performed the simulation and real experiments to verify the effectiveness of the proposed framework with the Sentinel-2 data, which simulated the different Widths.
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Urban Classification by the Fusion of Thermal Infrared Hyperspectral and Visible Data
Photogrammetric Engineering & Remote Sensing, 2015Co-Authors: Hongyan Zhang, Min Guo, Liangpei Zhang, Huanfeng ShenAbstract:Abstract The 2014 Data Fusion Contest, organized by the Image Analysis and Data Fusion (IADF) Technical Committee of the IEEE Geoscience and Remote Sensing Societ y , involved two datasets acquired at different spectral ranges and spatial resolutions: a coarser-resolution long-wave infrared (LWIR, thermal infrared) hyperspectral data set and fine-resolution data acquired in the visible (VIS) wavelength range. In this article, a novel multi-level fusion approach is proposed to fully utilize the characteristics of these two different datasets to achieve improved urban land-use and land-cover classification. Specificall y , road extraction by fusing the classification result of the TI-HSI dataset and the segmentation result of the VIS dataset is first proposed. Thereafter, a novel gap inpainting method for the VIS data with the guidance of the TI-HSI data is presented to deal with the Swath Width inconsistency, and to facilitate an accurate spatial feature extraction step. The experimental results with the 2014 Data Fusion Contest datasets suggest that the proposed method can alleviate the multi-spectral-spatial resolution and multi-Swath Width problem to a great extent, and achieve an improved urban classification accuracy.
Robert C. Levy - One of the best experts on this subject based on the ideXlab platform.
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Impact of satellite viewing-Swath Width on global and regional aerosol optical thickness statistics and trends
Atmospheric Measurement Techniques, 2014Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. LevyAbstract:Abstract. We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical thickness (AOT) product to assess the impact of reduced Swath Width on global and regional AOT statistics and trends. Along-track and across-track sampling strategies are employed, in which the full MODIS data set is sub-sampled with various narrow-Swath (~ 400–800 km) and single pixel Width (~ 10 km) configurations. Although view-angle artifacts in the MODIS AOT retrieval confound direct comparisons between averages derived from different sub-samples, careful analysis shows that with many portions of the Earth essentially unobserved, spatial sampling introduces uncertainty in the derived seasonal–regional mean AOT. These AOT spatial sampling artifacts comprise up to 60% of the full-Swath AOT value under moderate aerosol loading, and can be as large as 0.1 in some regions under high aerosol loading. Compared to full-Swath observations, narrower Swath and single pixel Width sampling exhibits a reduced ability to detect AOT trends with statistical significance. On the other hand, estimates of the global, annual mean AOT do not vary significantly from the full-Swath values as spatial sampling is reduced. Aggregation of the MODIS data at coarse grid scales (10°) shows consistency in the aerosol trends across sampling strategies, with increased statistical confidence, but quantitative errors in the derived trends are found even for the full-Swath data when compared to high spatial resolution (0.5°) aggregations. Using results of a model-derived aerosol reanalysis, we find consistency in our conclusions about a seasonal–regional spatial sampling artifact in AOT. Furthermore, the model shows that reduced spatial sampling can amount to uncertainty in computed shortwave top-of-atmosphere aerosol radiative forcing of 2–3 W m−2. These artifacts are lower bounds, as possibly other unconsidered sampling strategies would perform less well. These results suggest that future aerosol satellite missions having significantly less than full-Swath viewing are unlikely to sample the true AOT distribution well enough to obtain the statistics needed to reduce uncertainty in aerosol direct forcing of climate.
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Impact of satellite viewing Swath Width on global and regional aerosol optical thickness statistics and trends
2013Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. LevyAbstract:Abstract. We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical thickness (AOT) product to assess the impact of reduced Swath Width on global and regional AOT statistics and trends. Ten different sampling strategies are employed, in which the full MODIS dataset is sub-sampled with various narrow-Swath (~400–800 km) and curtain-like (~10 km) along-track configurations. Although view-angle artifacts in the MODIS AOT retrieval confound direct comparisons between averages derived from different sub-samples, careful analysis shows that with many portions of the Earth essentially unobserved, the AOT statistics of these sub-samples exhibit significant regional and seasonal biases. These AOT spatial sampling artifacts comprise up to 60% of the full-Swath AOT value under moderate aerosol loading, and can be as large as 0.1 in some regions under high aerosol loading. Compared to full-Swath observations, narrower Swaths exhibit a reduced ability to detect AOT trends with statistical significance, and for curtain-like sampling we do not find any statistically significant decadal-scale trends at all. An across-track sampling strategy obviates the MODIS view angle artifact, and its mean AOT converges to the full-Swath mean values for sufficiently coarse spatial and temporal aggregation. Nevertheless, across-track sampling has significant seasonal-regional sampling artifacts, leading to biases comparable to the curtain-like along-track sampling, lacks sufficient coverage to assign statistical significance to aerosol trends, and is not achievable with an actual narrow-Swath or curtain-like instrument. These results suggest that future aerosol satellite missions having significantly less than full-Swath viewing are unlikely to sample the true AOT distribution well enough to determine decadal-scale trends or to obtain the statistics needed to reduce uncertainty in aerosol direct forcing of climate.
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Implications of Satellite Swath Width on Global Aerosol Optical Thickness Statistics
2012Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. Levy, Ellsworth J. WeltonAbstract:Abstract. We assess the impact of Swath Width on the statistics of aerosol optical thickness (AOT) retrieved by satellite, as inferred from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS). Using collocated AERONET sun photometer observations we develop a correction to the MODIS data to account for calibration and algorithmic view angle dependency in the retrieved AOT. We sub-sample and correct the AOT data from the MODIS Aqua instrument along several candidate Swaths of various Widths for the years 2003–2011. We find that over ocean the global, annual mean AOT is within ± 0.01 of the full Swath AOT for all of our sub-samples. Over land, however, most of our sub-samples are outside of this criterion range in the global, annual mean. Moreover, at smaller spatial and temporal scales we find wide deviation in the sub-sample AOT relative to the full Swath over both land and ocean. In all, the sub-sample AOT is within ± 0.01 of the full Swath value less than 25% of the time over land, and less than 50% of the time over ocean (less than 35% for all but the widest of our sub-sample Swaths). These results suggest that future aerosol satellite missions having only narrow Swath views may not sample the true AOT distribution sufficiently to reduce significantly the uncertainty in aerosol direct forcing of climate.
Murzy D. Jhabvala - One of the best experts on this subject based on the ideXlab platform.
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IGARSS - Gimbaled, high resolution, city-level, thermal Infrared mapping from an Airship platform
2014 IEEE Geoscience and Remote Sensing Symposium, 2014Co-Authors: Xiuhong Sun, James C. Eichholz, Robert L. Fischer, Peter K. Shu, Murzy D. JhabvalaAbstract:A pilot effort adapting a gimbaled Long-Wavelength InfraRed (LWIR) imaging system prototype to the U.S. Navy MZ-3A Airship for high resolution thermal mapping of Baltimore, Maryland, has been performed. Using gimbaled step-staring imaging technologies, the Swath-Width of a small format, 320 by 256 pixel, 30μm pitch, Quantum Well Infrared Photodetector (QWIP) camera utilizing a 50mm lens has been effectively tripled. QWIP data collected from an airship platform resulted in a 60cm Ground Sample Distance (GSD) high quality LWIR thermal image with a 500m Swath-Width. The aerial LWIR images collected by the gimbaled system are geospatially accurate and rapidly deliverable for GIS mapping applications.
Peter R. Colarco - One of the best experts on this subject based on the ideXlab platform.
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Impact of satellite viewing-Swath Width on global and regional aerosol optical thickness statistics and trends
Atmospheric Measurement Techniques, 2014Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. LevyAbstract:Abstract. We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical thickness (AOT) product to assess the impact of reduced Swath Width on global and regional AOT statistics and trends. Along-track and across-track sampling strategies are employed, in which the full MODIS data set is sub-sampled with various narrow-Swath (~ 400–800 km) and single pixel Width (~ 10 km) configurations. Although view-angle artifacts in the MODIS AOT retrieval confound direct comparisons between averages derived from different sub-samples, careful analysis shows that with many portions of the Earth essentially unobserved, spatial sampling introduces uncertainty in the derived seasonal–regional mean AOT. These AOT spatial sampling artifacts comprise up to 60% of the full-Swath AOT value under moderate aerosol loading, and can be as large as 0.1 in some regions under high aerosol loading. Compared to full-Swath observations, narrower Swath and single pixel Width sampling exhibits a reduced ability to detect AOT trends with statistical significance. On the other hand, estimates of the global, annual mean AOT do not vary significantly from the full-Swath values as spatial sampling is reduced. Aggregation of the MODIS data at coarse grid scales (10°) shows consistency in the aerosol trends across sampling strategies, with increased statistical confidence, but quantitative errors in the derived trends are found even for the full-Swath data when compared to high spatial resolution (0.5°) aggregations. Using results of a model-derived aerosol reanalysis, we find consistency in our conclusions about a seasonal–regional spatial sampling artifact in AOT. Furthermore, the model shows that reduced spatial sampling can amount to uncertainty in computed shortwave top-of-atmosphere aerosol radiative forcing of 2–3 W m−2. These artifacts are lower bounds, as possibly other unconsidered sampling strategies would perform less well. These results suggest that future aerosol satellite missions having significantly less than full-Swath viewing are unlikely to sample the true AOT distribution well enough to obtain the statistics needed to reduce uncertainty in aerosol direct forcing of climate.
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Impact of satellite viewing Swath Width on global and regional aerosol optical thickness statistics and trends
2013Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. LevyAbstract:Abstract. We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical thickness (AOT) product to assess the impact of reduced Swath Width on global and regional AOT statistics and trends. Ten different sampling strategies are employed, in which the full MODIS dataset is sub-sampled with various narrow-Swath (~400–800 km) and curtain-like (~10 km) along-track configurations. Although view-angle artifacts in the MODIS AOT retrieval confound direct comparisons between averages derived from different sub-samples, careful analysis shows that with many portions of the Earth essentially unobserved, the AOT statistics of these sub-samples exhibit significant regional and seasonal biases. These AOT spatial sampling artifacts comprise up to 60% of the full-Swath AOT value under moderate aerosol loading, and can be as large as 0.1 in some regions under high aerosol loading. Compared to full-Swath observations, narrower Swaths exhibit a reduced ability to detect AOT trends with statistical significance, and for curtain-like sampling we do not find any statistically significant decadal-scale trends at all. An across-track sampling strategy obviates the MODIS view angle artifact, and its mean AOT converges to the full-Swath mean values for sufficiently coarse spatial and temporal aggregation. Nevertheless, across-track sampling has significant seasonal-regional sampling artifacts, leading to biases comparable to the curtain-like along-track sampling, lacks sufficient coverage to assign statistical significance to aerosol trends, and is not achievable with an actual narrow-Swath or curtain-like instrument. These results suggest that future aerosol satellite missions having significantly less than full-Swath viewing are unlikely to sample the true AOT distribution well enough to determine decadal-scale trends or to obtain the statistics needed to reduce uncertainty in aerosol direct forcing of climate.
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Implications of Satellite Swath Width on Global Aerosol Optical Thickness Statistics
2012Co-Authors: Peter R. Colarco, Lorraine A. Remer, Ralph A. Kahn, Robert C. Levy, Ellsworth J. WeltonAbstract:Abstract. We assess the impact of Swath Width on the statistics of aerosol optical thickness (AOT) retrieved by satellite, as inferred from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS). Using collocated AERONET sun photometer observations we develop a correction to the MODIS data to account for calibration and algorithmic view angle dependency in the retrieved AOT. We sub-sample and correct the AOT data from the MODIS Aqua instrument along several candidate Swaths of various Widths for the years 2003–2011. We find that over ocean the global, annual mean AOT is within ± 0.01 of the full Swath AOT for all of our sub-samples. Over land, however, most of our sub-samples are outside of this criterion range in the global, annual mean. Moreover, at smaller spatial and temporal scales we find wide deviation in the sub-sample AOT relative to the full Swath over both land and ocean. In all, the sub-sample AOT is within ± 0.01 of the full Swath value less than 25% of the time over land, and less than 50% of the time over ocean (less than 35% for all but the widest of our sub-sample Swaths). These results suggest that future aerosol satellite missions having only narrow Swath views may not sample the true AOT distribution sufficiently to reduce significantly the uncertainty in aerosol direct forcing of climate.
Nirmal Singh - One of the best experts on this subject based on the ideXlab platform.
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Performance of different nozzles for tractor mounted sprayers
Journal of research, 2006Co-Authors: Shashi K Singh, Surendra Singh, Vaishali Sharda, Nirmal SinghAbstract:A spray patternator was fabricated for the selection of a suitable nozzle, its height above the plant canopy and spacing between the nozzles for a tractor mounted sprayer to have uniform distribution of pesticide on the cotton crop. Experiments were conducted with three nozzles i.e. Triple Action Nozzle (TAN), Bi-Action Nozzle (BAN) and Hollow Cone Nozzle (HCN) at four different pressures of 2.5, 3.0, 3.5 and 4.0 kg/cm2, three spray heights of 40, 50 and 60 cm, and spacing of 40, 45 and 50 cm between nozzles. It was found that with the increase in pressure from 2.5 to 4.0 kg/cm2, maximum Swath, spray angle and discharge rate increased for all the three types of nozzles. At all working pressures, the triple action nozzle covered larger Width but discharge was more than that required for cotton crop. The average discharge rate for Bi-Action Nozzle varied from 369.4 to 477.3 ml/min and Swath Width increased from 78 to 87cm with the increase in pressure from 2.5 to 4.0 kg/cm2. The minimum coefficient of variation in spray distribution was obtained at a working pressure of 3.5 kg/cm2. For Hollow Cone Nozzle the Swath Width was smaller as compared to triple action and bi-action nozzles and the average discharge rate increased from 474.5 to 606.2 ml/min as the working pressure increased from 2.5 to 4.0 kg/cm2. At the pressure of 3.5 kg/cm2, the nozzle heights of 40 and 50 cm gave better coefficient of variations as 60.56 and 61.76 per cent, respectively. The Swath Width was more at nozzle height of 50 cm than that of 40 cm. Similarly, the nozzle spacing of 45 cm gave better Coefficient of Variation (10.18%) as compared to other spacing.
