Synergy between optical imaging radiometry and radar altimetry for inland waters: an experience with Sentinel-3 on the Nasser Lake

2020 ◽  
Author(s):  
Andrea Scozzari ◽  
Stefano Vignudelli ◽  
Mohamed Elsahabi ◽  
Neama Galal ◽  
Marwa Khairy ◽  
...  
Keyword(s):  
Land Surface ◽  
Morphological Changes ◽  
Morphological Characteristics ◽  
Ground Truth ◽  
Water Levels ◽  
Radar Altimeter ◽  
Radar Altimetry ◽  
Ground Truth Data ◽  
In Situ Data ◽  
Nasser Lake

<p>It is currently well known that a combination of stressors, such as climate change, human activities and new infrastructures might influence the storage capacity of strategic surface water reservoirs at a global level.</p><p>The Nasser Lake is the biggest and most important lake in Egypt, located in the southern part of the Nile River in Upper Egypt. The expected impact of the Grand Ethiopian Renaissance Dam (GERD) on the future availability of the Nile water, together with the significant and rapid water level variations and sedimentation processes, make the Nasser Lake a particularly challenging place to be monitored in the next years.</p><p>This work describes a preliminary study on the possible usage of the imaging radiometer SLSTR (Sea and Land Surface Temperature Radiometer) onboard Sentinel-3 for estimating water coverage extent in inland water contexts, in synergy with radar altimetry measurements provided by the SRAL (Synthetic aperture Radar ALtimeter) instrument. In particular, this work wants to exploit the simultaneous acquisition offered by SRAL and SLSTR instruments hosted by the Sentinel-3A/B platform.</p><p>We introduce an alternative technique to the classical calculation of the whole water extent based on high-resolution imagery, essentially intended for the application to wide-swath short-revisit sensors. The proposed approach starts from the hypothesis that a much-reduced subset of pixels may carry enough information for assessing the status of the observed water body by estimating the water coverage percent within each single pixel. Such an assumption can rely only on the radiometric performance of the instrument, SLSTR in this case.</p><p>The timeseries of water levels by the SRAL instrument were obtained by using the 20 Hz product generated by the SARvatore processor run on the ESA GPOD (Grid Processing On Demand) platform. A timeseries derived from SLSTR measurements has been generated by a simple feature extraction technique, based on the selection of pixels exhibiting the highest variability of the collected radiance. As expected, this subset essentially identifies particular spots on the coastlines of the target, as a consequence of its morphological characteristics.</p><p>Preliminary results show a promising relationship between the timeseries generated by the two independent measurements and between the available in situ data as well. Under the hypothesis of a time-invariant system (i.e., characterised by no significant morphological changes), once an area-level-volume relationship is identified, volume estimations can be inferred by either altimetric or radiometric measurements per se.</p><p>Thus, the simultaneous observation by the two instruments represents a relevant opportunity for cross-validating the acquired data. Moreover, the approximation experimented in this work gives the perspective of a very light computational process for expedite water storage estimations in large surface reservoirs, provided that the natural system is fully identified on the basis of ground-truth data.</p>

Estimating Regional Soil Moisture with Synergistic Use of AMSR2 and MODIS Images

2021 ◽  
Vol 87 (9) ◽  
pp. 649-660
Author(s):  
Majid Rahimzadegan ◽  
Arash Davari ◽  
Ali Sayadi
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Regional Scale ◽  
Ground Truth ◽  
Absolute Error ◽  
Simple Method ◽  
Ground Truth Data ◽  
Pi Index

Soil moisture content (SMC), product of Advanced Microwave Scanning Radiometer 2 (AMSR2), is not at an adequate level of accuracy on a regional scale. The aim of this study is to introduce a simple method to estimate SMC while synergistically using AMSR2 and Moderate Resolution Imaging Spectroradiometer (MODIS) measurements with a higher accuracy on a regional scale. Two MODIS products, including daily reflectance (MYD021) and nighttime land surface temperature (LST) products were used. In 2015, 1442 in situ SMC measurements from six stations in Iran were used as ground-truth data. Twenty models were evaluated using combinations of polarization index (PI), index of soil wetness (ISW), normalized difference vegetation index (NDVI), and LST. The model revealed the best results using a quadratic combination of PI and ISW, a linear form of LST, and a constant value. The overall correlation coefficient, root-mean-square error, and mean absolute error were 0.59, 4.62%, and 3.01%, respectively.

scholarly journals Global River Radar Altimetry Time Series (GRRATS): new river elevation earth science data records for the hydrologic community

2020 ◽  
Vol 12 (1) ◽  
pp. 137-150 ◽  
Author(s):  
Stephen Coss ◽  
Michael Durand ◽  
Yuchan Yi ◽  
Yuanyuan Jia ◽  
Qi Guo ◽  
...  
Keyword(s):  
Time Series ◽  
Earth Science ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Science Data ◽  
Radar Altimetry ◽  
In Situ Data ◽  
Virtual Station ◽  
Earth Science Data

Abstract. The capabilities of radar altimetry to measure inland water bodies are well established, and several river altimetry datasets are available. Here we produced a globally distributed dataset, the Global River Radar Altimeter Time Series (GRRATS), using Envisat and Ocean Surface Topography Mission (OSTM)/Jason-2 radar altimeter data spanning the time period 2002–2016. We developed a method that runs unsupervised, without requiring parameterization at the measurement location, dubbed virtual station (VS) level, and applied it to all altimeter crossings of ocean-draining rivers with widths >900 m (>34 % of the global drainage area). We evaluated every VS, either quantitatively for VS locations where in situ gages are available or qualitatively using a grade system. We processed nearly 1.5 million altimeter measurements from 1478 VSs. After quality control, the final product contained 810 403 measurements distributed over 932 VSs located on 39 rivers. Available in situ data allowed quantitative evaluation of 389 VSs on 12 rivers. The median standard deviation of river elevation error is 0.93 m, Nash–Sutcliffe efficiency is 0.75, and correlation coefficient is 0.9. GRRATS is a consistent, well-documented dataset with a user-friendly data visualization portal, freely available for use by the global scientific community. Data are available at https://doi.org/10.5067/PSGRA-SA2V1 (Coss et al., 2016).

scholarly journals Land Surface Temperature Retrieval from LANDSAT-8 Ther-mal Infrared Sensor Data and Validation with Infrared Ther-mometer Camera

2018 ◽  
Vol 7 (4.20) ◽  
pp. 601
Author(s):  
Muhammad Mejbel Salih ◽  
Oday Zakariya Jasim ◽  
Khalid I. Hassoon ◽  
Aysar Jameel Abdalkadhum
Keyword(s):  
Land Cover ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Ground Truth ◽  
Sensor Data ◽  
Landsat 8 ◽  
Infrared Sensor ◽  
Ground Truth Data ◽  
Land Cover Types

This paper illustrates a proposed method for the retrieval of land surface temperature (LST) from the two thermal bands of the LAND-SAT-8 data. LANDSAT-8, the latest satellite from Landsat series, launched on 11 February 2013, using LANDSAT-8 Operational Line Imager and Thermal Infrared Sensor (OLI & TIRS) satellite data. LANDSAT-8 medium spatial resolution multispectral imagery presents particular interest in extracting land cover, because of the fine spectral resolution, the radiometric quantization of 12 bits. In this search a trial has been made to estimate LST over Al-Hashimiya district, south of Babylon province, middle of Iraq. Two dates images acquired on 2nd &18th of March 2018 to retrieve LST and compare them with ground truth data from infrared thermometer camera (all the meas-urements contacted with target by using type-k thermocouple) at the same time of images capture. The results showed that the rivers had a higher LST which is different to the other land cover types, of less than 3.47 C ◦, and the LST different for vegetation and residential area were less than 0.4 C ◦ with correlation coefficient of the two bands 10 and 11 Rbnad10= 0.70, Rband11 = 0.89 respectively, for the im-aged acquired on the 2nd of march 2018 and Rband10= 0.70 and Rband11 = 0.72 on the 18th of march 2018. These results confirm that the proposed approach is effective for the retrieval of LST from the LANDSAT-8 Thermal bands, and the IR thermometer camera data which is an effective way to validate and improve the performance of LST retrieval. Generally the results show that the closer measure-ment taken from the scene center time, a better quality to classify the land cover. The purpose of this study is to assess the use of LAND-SAT-8 data to specify temperature differences in land cover and compare the relationship between land surface temperature and land cover types.

scholarly journals The 10-m crop type maps in Northeast China during 2017–2019

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Nanshan You ◽  
Jinwei Dong ◽  
Jianxi Huang ◽  
Guoming Du ◽  
Geli Zhang ◽  
...  
Keyword(s):  
Land Surface ◽  
Northeast China ◽  
Time Series Data ◽  
Ground Truth ◽  
Series Data ◽  
Ground Truth Data ◽  
Production Region ◽  
Mapping Strategy ◽  
Crop Type ◽  
Texture Characteristics

AbstractNortheast China is the leading grain production region in China where one-fifth of the national grain is produced; however, consistent and reliable crop maps are still unavailable, impeding crop management decisions for regional and national food security. Here, we produced annual 10-m crop maps of the major crops (maize, soybean, and rice) in Northeast China from 2017 to 2019, by using (1) a hierarchical mapping strategy (cropland mapping followed by crop classification), (2) agro-climate zone-specific random forest classifiers, (3) interpolated and smoothed 10-day Sentinel-2 time series data, and (4) optimized features from spectral, temporal, and texture characteristics of the land surface. The resultant maps have high overall accuracies (OA) spanning from 0.81 to 0.86 based on abundant ground truth data. The satellite estimates agreed well with the statistical data for most of the municipalities (R2 ≥ 0.83, p < 0.01). This is the first effort on regional annual crop mapping in China at the 10-m resolution, which permits assessing the performance of the soybean rejuvenation plan and crop rotation practice in China.

scholarly journals Global River Radar Altimetry Time Series (GRRATS): New River Elevation Earth Science Data Records for the Hydrologic Community

2019 ◽  
Author(s):  
Stephen Coss ◽  
Michael Durand ◽  
Yuchan Yi ◽  
Yuanyuan Jia ◽  
Qi Guo ◽  
...  
Keyword(s):  
Time Series ◽  
Earth Science ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Science Data ◽  
Radar Altimetry ◽  
In Situ Data ◽  
Virtual Station ◽  
Earth Science Data

Abstract. The capabilities of radar altimetry to measure inland water bodies are well established and several river altimetry datasets are available. Here we produced a globally-distributed dataset, the Global River Radar Altimeter Time Series (GRRATS), using Envisat and Ocean Surface Topography Mission (OSTM)/Jason-2 radar altimeter data spanning the time period 2002–2016. We developed a method that runs unsupervised, without requiring parameterization at the measurement location, dubbed virtual station (VS) level and applied it to all altimeter crossings of ocean draining rivers with widths > 900 m (> 34 % of global drainage area). We evaluated every VS, either quantitatively for VS where in-situ gages are available, or qualitatively using a grade system. We processed nearly 1.5 million altimeter measurements from 1,478 VS. After quality control, the final product contained 810,403 measurements distributed over 932 VS located on 39 rivers. Available in-situ data allowed quantitative evaluation of 389 VS on 12 rivers. Median standard deviation of river elevation error is 0.93 m, Nash-Sutcliffe efficiency is 0.75, and correlation coefficient is 0.9. GRRATS is a consistent, well-documented dataset with a user-friendly data visualization portal, freely available for use by the global scientific community. Data are available at DOI 10.5067/PSGRA-SA2V1 (Durand et al., 2016).

scholarly journals Consistency of Radiometric Satellite Data over Lakes and Coastal Waters with Local Field Measurements

2020 ◽  
Vol 12 (4) ◽  
pp. 616 ◽  
Author(s):  
Krista Alikas ◽  
Ilmar Ansko ◽  
Viktor Vabson ◽  
Ave Ansper ◽  
Kersti Kangro ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Atmospheric Correction ◽  
Field Measurements ◽  
Ground Truth ◽  
Local Data ◽  
Ground Truth Data ◽  
In Situ Data ◽  
Global Coverage

The Sentinel-3 mission launched its first satellite Sentinel-3A in 2016 to be followed by Sentinel-3B and Sentinel-3C to provide long-term operational measurements over Earth. Sentinel-3A and 3B are in full operational status, allowing global coverage in less than two days, usable to monitor optical water quality and provide data for environmental studies. However, due to limited ground truth data, the product quality has not yet been analyzed in detail with the fiducial reference measurement (FRM) dataset. Here, we use the fully characterized ground truth FRM dataset for validating Sentinel-3A Ocean and Land Colour Instrument (OLCI) radiometric products over optically complex Estonian inland waters and Baltic Sea coastal areas. As consistency between satellite and local data depends on uncertainty in field measurements, filtering of the in situ data has been made based on the uncertainty for the final comparison. We have compared various atmospheric correction methods and found POLYMER (POLYnomial-based algorithm applied to MERIS) to be most suitable for optically complex waters under study in terms of product accuracy, amount of usable data and also being least influenced by the adjacency effect.

scholarly journals Identification of Crop Type in Crowdsourced Road View Photos with Deep Convolutional Neural Network

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1165
Author(s):  
Fangming Wu ◽  
Bingfang Wu ◽  
Miao Zhang ◽  
Hongwei Zeng ◽  
Fuyou Tian
Keyword(s):  
State Of The Art ◽  
Ground Truth ◽  
Decision Fusion ◽  
Identification Accuracy ◽  
Deep Convolutional Neural Networks ◽  
Ground Truth Data ◽  
In Situ Data ◽  
Crop Type ◽  
Crop Types

In situ ground truth data are an important requirement for producing accurate cropland type map, and this is precisely what is lacking at vast scales. Although volunteered geographic information (VGI) has been proven as a possible solution for in situ data acquisition, processing and extracting valuable information from millions of pictures remains challenging. This paper targets the detection of specific crop types from crowdsourced road view photos. A first large, public, multiclass road view crop photo dataset named iCrop was established for the development of crop type detection with deep learning. Five state-of-the-art deep convolutional neural networks including InceptionV4, DenseNet121, ResNet50, MobileNetV2, and ShuffleNetV2 were employed to compare the baseline performance. ResNet50 outperformed the others according to the overall accuracy (87.9%), and ShuffleNetV2 outperformed the others according to the efficiency (13 FPS). The decision fusion schemes major voting was used to further improve crop identification accuracy. The results clearly demonstrate the superior accuracy of the proposed decision fusion over the other non-fusion-based methods in crop type detection of imbalanced road view photos dataset. The voting method achieved higher mean accuracy (90.6–91.1%) and can be leveraged to classify crop type in crowdsourced road view photos.

Characteristics of the course of nephritis associated with Iga-vasculitis Henoch-Schoenlein in children

2020 ◽  
Vol 24 (3) ◽  
pp. 64-71
Author(s):  
A. V. Sukalo ◽  
I. A. Kazyra
Keyword(s):  
Clinical Laboratory ◽  
Morphological Changes ◽  
Pediatric Nephrology ◽  
Morphological Characteristics ◽  
Lymphocyte Activation ◽  
Renal Tissue ◽  
Kidney Damage ◽  
Iga Vasculitis ◽  
Factors Affecting ◽  
Treatment Regimens

INTRODUCTION. Among systemic vasopathies in children, IgA vasculitis Henoch Schoenlein (HS) is the most common, according to various authors, kidney damage is noted in 25-80 % and usually determines the prognosis of the disease.THE AIM of the study was to analyze clinical, laboratory, immunological, morphological characteristics, features of the course and treatment of nephritis associated with IgA vasculitis HS in children, as well as factors affecting the prognosis.PATIENTS AND METHODS. The study included 31 patients with morphologically verified nephritis due to IgA vasculitis HS (18 – boys, 13 – girls) aged 3 to 17 years, who were monitored at the Nephrology Department of the "2nd Children's City Clinical Hospital" of the National Center for Pediatric Nephrology and Renal Replacement therapy in Minsk from 2010 to 2019 yrs.The following parameters were analyzed: the clinical variant of kidney damage, laboratory tests (including the study of BAFF, RANTES lymphocyte activation molecules, pro-inflammatory IL1β, caspase1, TNFα, growth factors VEGF, TGF), 24 hours monitoring and office blood pressure measurements, ECHO cardiography with indicescalculation, ultrasound of the carotid arteries with the thickness of intima-media complex, morphological changes in the renal tissue, as well as treatment regimens.RESULTS. The contribution of deGal-IgA1, markers of T and B lymphocytes activation, pro-inflammatory and profibrotic molecules in the development of the disease is shown. Arterial hypertension was registered in 42 % of children, signs of heart remodeling according to the calculated indices in 19,3 %. Decrease level of adiponectin, vitamin D, leptin, increase concentration of obestatin, Pro-BNP, hs-CRP, and TSAT indicator classify patients with nephritis due to IgA vasculitis HS at moderate risk for the developmentof cardio-vascular disorders, which suggests the need for timely correction.CONCLUSION. In most cases, nephritis with IgA vasculitis HS has a benign course with rare relapses and progression to the end stage of chronic kidney disease (6,5 %).

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