Search results for "REMOTE"
showing 10 items of 1455 documents
Evaluation of saliva as a complementary technique to the diagnosis of COVID-19:a systematic review
2021
Background Infectious disease coronavirus 2019 (COVID-19) is caused by the SARS-CoV-2 virus, and it mainly affects the upper respiratory tract. The gold standard for its diagnosis is real-time reverse transcription polymerase chain reaction (RT-qPCR) performed on a nasopharyngeal swab. In contrast, testing saliva has significant advantages as a diagnostic method. Material and Methods We searched for articles evaluating saliva as a diagnostic method for COVID-19 on the PUBMED/MEDLINE, WEB OF SCIENCE, COCHRANE, and SCIELO platforms. We initially found 233 articles and 20 were selected for inclusion following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol: 18 c…
A Single-Channel Algorithm for Land-Surface Temperature Retrieval From ASTER Data
2010
This letter presents an adaptation to Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data of the generalized single-channel (SC) algorithm developed by JimE?nez-MuN?oz and Sobrino, also adapted to the Landsat thermal-infrared (TIR) channel (band 6) later by JimE?nez-MuN?oz The SC algorithm relies on the concept of atmospheric functions (AFs), which are dependent on atmospheric transmissivity, upwelling, and downwelling atmospheric radiances. These AFs are fitted versus the atmospheric water-vapor content for operational purposes, despite the fact that other computation options are also possible. The SC algorithm has been adapted to ASTER TIR bands 13 (10.659 ?m) and …
Multisensor comparison of NDVI for a semi‐arid environment in Spain
2009
The joint use of multiresolution sensors from different satellites offers many opportunities to describe vegetation and its dynamics. This paper introduces the concept of a virtual constellation (defined as an ensemble of all Earth Observation satellites in orbit that satisfy common requirements) for agricultural applications and contributes to providing the necessary inter-sensor calibration methodology for spectral reflectances and NDVI. For this purpose, we performed an observational study, comparing reflectances and the Normalized Difference Vegetation Index (NDVI), from near-synchronous image pairs of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), as the reference sensor and Landsat 5…
Improved land surface emissivities over agricultural areas using ASTER NDVI
2006
Abstract Land surface emissivity retrieval over agricultural regions is important for energy balance estimations, land cover assessment and other related environmental studies. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) produces images of sufficient spatial resolution (from 15 m to 90 m) to be of use in agricultural studies, in which fields of crops are too small to be well-resolved by low resolution sensors. The ASTER project generates land surface emissivity images as a Standard Product (AST05) using the Temperature/Emissivity Separation (TES) algorithm. However, the TES algorithm is prone to scaling errors in estimating emissivities for surfaces with low s…
Accuracy of ASTER Level-2 thermal-infrared Standard Products of an agricultural area in Spain
2007
Abstract The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) collects five-channel thermal-infrared images that are calibrated, corrected for atmospheric effects, and then converted to land surface temperature and emissivity products by the ASTER Temperature/Emissivity Separation (TES) algorithm. TES scales low- and high-contrast surfaces differently, and has been validated over water (low contrast) and rock (high contrast). Performance of TES over agricultural areas, however, has not been evaluated specifically. To address this issue, field measurements of “ground truth” were made over bare soil in addition to green grass, alfalfa and corn, at an agricultural researc…
Atmospheric water vapor content over land surfaces derived from the AVHRR data: application to the Iberian Peninsula
1999
A study has been carried out using simulated NOAA/advanced very high resolution radiometer (AVHRR) data at 11 and 12 /spl mu/m (with LOWTRAN-7, MODTRAN 2.0, and the TIGR database), AVHRR images of the Iberian Peninsula and the Palma de Mallorca Island, radiosonde observations at seven meteorological stations, and the AVISO database provided by Meteo France to describe, compare, and analyze two different approaches for estimating the total atmospheric water vapor content (W) over land surfaces from AVHRR data. These two techniques are: 1) the split-window covariance-variance ratio (SWCVR), based on a quadratic relationship between W and the ratio of the spatial covariance and variance of bri…
Split-Window Coefficients for Land Surface Temperature Retrieval From Low-Resolution Thermal Infrared Sensors
2008
In this letter, we provide a complete set of split-window coefficients that can be used to retrieve land surface temperature (LST) from thermal infrared sensors onboard the most popular remote-sensing satellites: ERS-ATSR2, ENVISAT-AATSR, Terra/Aqua-MODIS, NOAA series-AVHRR, METOP-AVHRR3, GOES series-IMAGER, and MSG1/MSG2-SEVIRI. The coefficients have been obtained by minimization from an extensive simulated database constructed from MODTRAN radiative transfer code calculations, emissivity spectra extracted from spectral libraries, and spectral response functions of the thermal bands considered. This letter also analyzes the magnitude of the error on the LST retrieval and the contribution t…
Vegetation dynamics from NDVI time series analysis using the wavelet transform
2009
A multi-resolution analysis (MRA) based on the wavelet transform (WT) has been implemented to study NDVI time series. These series, which are non-stationary and present short-term, seasonal and long-term variations, can be decomposed using this MRA as a sum of series associated with different temporal scales. The main focus of the paper is to check the potential of this MRA to capture and describe both intra- and inter-annual changes in the data, i.e., to discuss the ability of the proposed procedure to monitor vegetation dynamics at regional scale. Our approach concentrates on what wavelet analysis can tell us about a NDVI time series. On the one hand, the intra-annual series, linked to th…
Emissivity measurements of several soils and vegetation types in the 8–14, μm Wave band: Analysis of two field methods
1997
Abstract The two variants of the box method (with one and two lids) has been rigorously analyzed. As a result of this analysis, a correction factor that takes into account the nonideality of the materials used for the box, as well as its geometry, has been derived A simple method for determining the effective downward atmospheric temperature that uses only the temperature measurement at the zenith also has been proposed. Finally, by using one of the two variants of the box method, 72 in situ emissivity measurements in the 8–14 pin wave-band region of typical vegetation, soils, and rocks of Europe and South America, has been obtained. The use of these data for the ernissivity correction of s…
Study of Temperature Heterogeneities at Sub-Kilometric Scales and Influence on Surface–Atmosphere Energy Interactions
2019
The retrieval of land surface temperature (LST) from remote sensing techniques has been studied and validated during the past 40 years, leading to important improvements. Accurate LST values are currently obtained through measurements using medium resolution thermal infrared (TIR) sensors. However, the most recent review reports demonstrated that the future TIR LST products need to obtain reliable temperature values at a high spatial resolution (100 m or higher) to study temperature variations between different elements in a heterogeneous kilometric area. The launch of high-resolution TIR sensors in the near future requires studies of the temporal evolution and spatial heterogeneities of th…