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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Cross-Comparison of Three SAR Soil Moisture Retrieval Algorithms Using Synthetic and Experimental Data
摘要： The objective of this study is to cross-compare three algorithms for retrieving surface soil moisture (SSM) from ESA’s Sentinel-1 (S-1) data. The context is provided by the large scientific and application interest in SSM products at high resolution and regional/continental scale that can be retrieved from S-1 data alone or in combination with other missions such as NASA/SMAP and ESA/SMOS. Of the three investigated algorithms, one inverts a scattering model exploiting a Bayesian approach, whereas the other two are change detection approaches. The cross-comparison is carried out by using both simulated and experimental data. Strengths and weaknesses of the three algorithms are identified and discussed.
关键词： Algorithm comparison,Soil Moisture,Sentinel-1,Validation
更新于2025-09-09 09:28:46
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Annual dynamics of shortwave radiation of bare arable lands on a global scale incorporating their roughness
摘要： Smoothing soil surfaces, which had previously been deeply plowed, increases their albedo, which results in a lower amount of shortwave radiation being absorbed by their surface layer. Those surfaces emit less long-wave radiation too, leading to a reduction in their surface temperature, which can affect the climate. This paper quantitatively estimates the highest possible amount of shortwave radiation that could be reflected throughout the year from bare soils on arable land in the most extensive agricultural regions, where major crops are cultivated, on six of the Earth’s continents. The estimation refers to the highest levels of soil radiation occurring during clear-sky conditions without any clouds when the surfaces that had been conventionally tilled were bare for several days or more after the day of planting and were air-dried in two extreme roughness states: those formed by a plow and a smoothing harrow. The annual dynamics of reflective shortwave radiation of the bare soils were obtained using vectorized and rasterized geostatistical data sets about the areas of the soils and periods when they were bare, as well the spectra of the soil units that occupied the majority of these areas. Adding together all of the diurnal amounts of shortwave radiation reflected from the bare soils for each of the regions in the world, it was found that their radiation peak, appearing on the 140th days of the year, can reach about 22 EJ/day for soils treated by a plow, and a further 3 EJ/day when they are smoothed by a smoothing harrow.
关键词： Shortwave radiation,Soil roughness,Bare soil albedo,Annual variations
更新于2025-09-04 15:30:14
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Hyperspectral inversion of heavy metal content in reclaimed soil from a mining wasteland based on different spectral transformation and modeling methods
摘要： Conventional methods for investigating heavy metal contamination in soil are time consuming and expensive. We explored reflectance spectroscopy as an alternative method for assessing heavy metals. Four spectral transformation methods, first-order differential (FDR), second-order differential (SDR), continuum removal (CR) and continuous wavelet transform (CWT), are used for the original spectral data. Spectral preprocessing effectively eliminated the noise and baseline drifting and also highlighted the locations of the spectral feature bands. Partial least squares regression (PLSR) and radial basis function neural network (RBF) were used to study the hyperspectral inversion of four heavy metals (Cr, As, Ni, Cd). The inversion models of four heavy metals were established in the bands with the highest correlation coefficient. The inversion effects were evaluated by the coefficient of determination (R2), root mean square error (RMSE) and residual predictive deviation (RPD) indexes. The R values of the correlation coefficient were significantly improved after smoothing and spectral transformation compared to the original waveband. The method combining continuous wavelet transform (CWT) with radial basis function neural network (RBF) had the best inversion effect on the four heavy metals. When compared to partial least squares regression (PLSR), the RMSE values were reduced by approximately 2. The CWT-RBF method can be used as a means of inversion of heavy metals in mining wasteland reclaimed land.
关键词： Continuous Wavelet Transform,Heavy metal,Spectral analysis,Radial Basis Function Neural Network,Reclamation soil
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Dual Circularly Polarized Antennas with Low Cross-Polarization for GNSS-R Applications
摘要： Global Navigation System-Reflectometry (GNSS-R), has gained increasing interests as an efficient tool for remote sensing. It is based on the concept of utilizing the received signals reflected from the Earth’s surface. Several GNSS-R system configurations were proposed depending on different retrieval algorithms. In a GNSS-R system, the antenna plays a key role as a receiving component. In this paper, in-situ measurements using a commercial dual circular polarized antenna receiving both the left-hand and right-hand circular polarization reflected from the ground are analyzed. A low cost and compact dual-port circular polarized patch antenna is designed and realized to overcome the limitations of the previous configuration. The prototype shows a low level of cross polarization suitable for GNSS-R application.
关键词： circular polarization,dual polarization,patch antenna,remote sensing of soil,GNSS-R
更新于2025-09-04 15:30:14
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Analysis of Vegetation Optical Depth and Soil Moisture Retrieved by SMOS Over Tropical Forests
摘要： In this letter, the results obtained with the last version (level 2, version 650) of SMOS retrieval algorithm are compared against independent measurements, over tropical forests. In particular, the climate research unit meteorological variables and data bases of forest height and forest biomass are considered. Comparisons with results obtained by AMSR-2 under similar conditions are also illustrated. Vegetation optical depth shows a generally good correlation with forest height and forest biomass, particularly in Africa and South America. Spatial and temporal trends of retrieved soil moisture follow trends of rainfall, particularly in regions of dry winter.
关键词： soil moisture (SM),SMOS,vegetation optical depth (VOD),tropical forests
更新于2025-09-04 15:30:14
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Spectral indices for the detection of salinity effects in melon plants
摘要： Water scarcity and soil salinization affect large semiarid agricultural areas throughout the world. The maintenance of agricultural productivity implies better agricultural practices and a careful selection of resistant crops. A proper monitoring of the physiological status of plants can lead to better knowledge of plant nutritional requirements. Visible and near-infrared (VNIR) radiometry provides a non-destructive and quantitative method to monitor vegetation status by quantifying chemical properties using spectroscopic techniques. In this study, the capability of VNIR spectral measurements to detect salinity effects on melon (Cucumis melo L.) plants was tested. Melon plants were cultivated under multiple soil salinity conditions (electrical conductivity, (EC)1:5: 0.5, 1.0 and 2.5 dS m–1). Spectral data of leaves were transformed into vegetation indices indicative of the physiological status of the plants. The results showed differences for N (p < 0.05), K and Na content (p < 0.01) due to salinity suggesting different degrees of salt stress on the plants. Specific leaf area increased with salinity levels (p < 0.001). The capabilities of VNIR radiometry to assess the influence of soil salinity on melon physiology using a non-destructive method were demonstrated. A normalized difference vegetation index (NDVI750-705), and the ratio between water index (WI) and normalized difference vegetation index (WI/NDVI750-705) showed significant relationships (p < 0.01) with the salinity. Therefore, this method could be used for in-situ early detection of salinity stress effects.
关键词： VNIR radiometry,Cucumis melo L.,saline soil
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Parametrization of a Dielectric Mixture Model to Retrieve Soil Moisture at Field Scale Using Sentinel-1 Data and in Situ Soil Moisture Measurements
摘要： In the framework of the H2020 APOLLO project a significant focus has been put on the use of high resolution satellite based products to serve small farmers in their agricultural practices. This paper presents first results achieved by using Sentinel-1 Synthetic Aperture Radar (SAR) data as input to a semi-empirical soil moisture (SM) retrieval model based on an algorithm originally developed for ERS SAR data and successively modified to handle ENVISAT ASAR acquisitions. In this work the model has been adapted to Sentinel-1 images and calibrated by using ground measurements taken in two test sites characterized by bare soil and cotton cultivation, aiming at testing its capability to represent the SM behavior at different stages of the vegetation cycle. The model performance has been assessed through the correlation R and root mean squared error (RMSE) between in situ and satellite retrieved SM data. Very good results have been achieved for bare soil (R>0.8, RMSE<0.04 m3m-3); however, the model performed worse in the cotton fields (R<0.6, RMSE>0.08 m3m-3).
关键词： Soil moisture,SAR,Sentinel-1,agricultural fields
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Remote Sensing of Root-Zone Soil Moisture Using I- and P-Band Signals of Opportunity: Instrument Validation Studies
摘要： Root zone soil moisture (RZSM) is an essential variable in meteorology, hydrology, and agriculture. A penetration depth sufficient to sense RZSM requires frequencies below about 500 MHz (I- and P-band). Active or passive microwave sensing in these bands presents substantial technical challenges due to antenna size, radio frequency interference (RFI) and competition for spectrum. Bistatic radar using Signal of Opportunity (SoOp) (e.g. digital satellite transmitters) offers an alternative approach, through reutilizing powerful signals already occupying bands allocated for communications. Airborne experiments using 240-270 MHz sources were conducted in October 2016, followed by a campaign using 360-380 MHz from a fixed tower location in an agricultural research site during the 2017 growing season. A new campaign that will also include I-band (137 MHz) is presently being installed in advance of the 2018 season. This paper will summarize activities to support the reduction of data from these campaigns and development of soil moisture profile retrievals.
关键词： Soil Moisture,hydrology,signals of opportunity,bistatic radar
更新于2025-09-04 15:30:14
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A Fiber Bragg-Grating-Based Miniature Sensor for the Fast Detection of Soil Moisture Profiles in Highway Slopes and Subgrades
摘要： A fiber Bragg grating (FBG)-based aluminum oxide tube packed sensor (ATPS) was developed for the fast detection of the soil moisture profile in highway slopes and subgrades. The novel ATPS consists of an aluminum oxide tube with a diameter of 5 mm, an optical fiber containing a quasi-distributed FBG sensors, a “U”-shaped resistance wire, and a flange. There are four 0.9-mm diameter holes in the ATPS. Laboratory experiments were carried out to calibrate the relationship between the thermal response of ATPS and the soil moisture content. Two laboratory rainfall validation model tests were performed to validate the ATPS for capturing the soil moisture profile in highway slopes and subgrades. During the validations, the accuracy of the ATPS was quantified, and water infiltration through grassy and grassless ground surfaces were investigated. The calibrations indicate that the ATPS can detect and record real-time changes in the highway slope and subgrade moisture after rainfall, and reveal the most dangerous zones that occur at the connection between different construction materials. The average measurement accuracy of soil moisture monitoring was 0.015 m3/m3. Please note that the connection is where cracks form easily and the soil hydraulic conductivity increases significantly. The test results also indicate that grassy cover (lawn) significantly prevents water infiltration during the first few minutes of rainfall (twelve minutes in this study), after which, however, the infiltration rate drops sharply. The influence of lawn on water infiltration depends on the soil structure, hydraulic conductivity, and rainfall time. In summary, due to its small size and fast detection, the ATPS is a portable probe that can be used for moisture monitoring in highway slopes and subgrades.
关键词： temperature sensing,aluminum oxide tube packed sensor (ATPS),highway slope and subgrade,fiber Bragg grating (FBG),soil moisture
更新于2025-09-04 15:30:14