esa-sceva/satcom-chunk-collection huggingface dataset:
###### Abstract  
Human activities coupled with climate change impacts are becoming the main factors in decreasing inland surface water quantity and quality, leading to the disturbance of the aquatic ecological balance. Under such conditions, the introduction and proliferation of aquatic invasive alien species are more likely to occur. Hence, frequent surface water quality monitoring is required for aquatic ecosystem sustainability. The main objectives of the present study are to analyze the seasonal variation in the invasive plant species water hyacinth (_Pontederia crassipes_) and biogeochemical water quality parameters, i.e., chlorophyll-a (Chl-a) and total suspended matter (TSM), and to examine their relationship in Lake Tana (Ethiopia) during a one-year study period (2020). Sentinel-2A/B satellite images are used to monitor water hyacinth expansion and Chl-a and TSM concentrations in the water. The Case 2 Regional Coast Colour processor (C2 RCC) is used for atmospheric and sunlight correction over inland waters, while the Sen2 Cor atmospheric processor is used to calculate the normalized difference vegetation index (NDVI) for water hyacinth mapping. The water hyacinth cover and biomass are determined by NDVI values ranging from 0.60 to 0.95. A peak in cover and biomass is observed in October 2020, just a month after the peak of Chl-a (25.2 mg m\({}^{-3}\)) and TSM (62.5 g m\({}^{-3}\)) concentrations observed in September 2020 (end of the main rainy season). The influx of sediment and nutrient load from the upper catchment area during the rainy season could be most likely responsible for both Chl-a and TSM increased concentrations. This, in turn, created a fertile situation for water hyacinth proliferation in Lake Tana. Overall, the freely available Sentinel-2 satellite imagery and appropriate atmospheric correction processors are an emerging potent tool for inland water monitoring and management in large-scale regions under a global change scenario.  
Copernicus programme; invasive alien species; water hyacinth; chlorophyll-a; total suspended matter; inland water monitoring 202214492114921[[https://doi.org/10.3390/rs14194921](https://doi.org/10.3390/rs14194921)]([https://doi.org/10.3390/rs14194921](https://doi.org/10.3390/rs14194921))
## 2 Literature Review
The validation results revealed that the models fit the observed data well; the validation results are summarized in Table 1. As a result, the modified models may be used to compute clear sky GHI in these study locations as well as other places with comparable climatic conditions. Between 2010 and 2013, [PERSON] et al. [59] evaluated the performance of three models for predicting GHI in Tetouan, northern Morocco: ASHRAE [60; 61], the [PERSON] model [62], and the [PERSON] model [63] which is also known as the Liu and Jordan model [64]. The authors observed that the ASHRAE model was more suited for estimating high-temporal resolution GHI, whereas the Campbell model was better suited for estimating monthly GHI at the study site. [PERSON] and [PERSON] [65] examined the estimated clear sky GHI in Finland using four models with different meteorological inputs. Aerosol Optical Depth and water vapour were the key meteorological inputs from the MACC and ERA-Interim reanalysis repositories, and almost all models underestimated GHI at the locations studied. [PERSON] [38; 44],[PERSON] [30; 31], and Solis with default Pvlib inputs [30; 66] all performed better. The inclusion of reanalysis inputs increased the Solis model's biases, which were caused by atmospheric optical depth (AOD) and water vapour climatology, both of which fail to accurately represent variability in specific locations and times. [PERSON] et al. [5] validated three GHI clear sky models adapted to the Madrid region. The validation was carried out by comparing the performance of the original and locally adapted models in estimating GHI; the results are summarized in Table 1. It was discovered that when the models were locally calibrated, there was a 4% improvement. They recommended that the study's calibration methodology be applied to areas with comparable climatic conditions. The study by [PERSON] et al. [57] examined fifty-four GHI clear-sky models, which is a significantly larger sample size than any previous work. The complexity of the models in the sample ranged from very simple to complex. Most of the models investigated have already been validated in various geographical areas at various periods and by using diverse validation methodologies. It is yet unknown how they correlate in a specific and uniform environment. The following limitations hindered the study: the input data required by the models did not correspond to what was available for the place and time, and the authors lacked the metadata that would have informed them about the accuracy of the data. As a result, missing data were generated by interpolation, extrapolation, or estimation, resulting in uncertainty in estimated GHI due to the inadequate information. [PERSON]'s [4] study examined methods for identifying clear-sky times in the literature; the approach used a wide variety of inputs. Using data from a few days with varying cloudiness, the author found that various methods had advantages and disadvantages.
## 3 Results
### Ecological Parameter Changes Considering LUTs
The NDVI, EVI, and NPP of water bodies, as well as the GPP and NPP of construction land, showed an increase. Conversely, the LAls of both LUTs experienced a significant decrease. The ecological parameters of unutilized land increased in many sub-regions, although the NPP in the NWC and NC regions decreased. The substantial area of unutilized land in the NWC and NC regions contributed to a minor decrease in the NPP of unutilized land in China. In summary, all ecological parameters of cultivated land and grassland increased in China and its sub-regions. However, the ecological parameters of forests in the QT region and the NPP of forests in the SC and SWC regions decreased. Additionally, the LAls of water bodies and construction land in each sub-region experienced a considerable decrease. This study not only compared the average values and change rates of ecological parameters across various LUTs, but also conducted an additional analysis of the distribution of their numerical intervals (Figure 8). The findings reveal that ecological parameters related to water bodies, construction land, and unutilized land tend to be concentrated in lower value ranges compared to cultivated land, forest, and grassland. When LUTs were not taken into account, the proportion of ecological parameters in the highest value range varied between 0.15% and 22.65%, while the proportion in the lowest value range ranged from 1.64% to 34.70%. Forest exhibited a higher proportion of high ecological parameters compared to other LUTs, with proportions in the highest value range ranging from 1.03% to 77.69%. In contrast, cultivated land showed a more evenly distributed proportion of ecological parameters across different value ranges. Unutilized land had the lowest proportion of ecological parameters in the highest value range among non-vegetation regions. Additionally, except for the LAI, water bodies generally had a higher proportion of ecological parameters in the low-value range compared to construction land. Figure 7: The average and slope values of ecological parameters of various LUTs in China and its sub-regions in 2001–2020. Figure 8: The proportion of numerical intervals of ecological parameters of various LUTs in China in 2001–2020. In summary, this section initially involves an examination of the average values and trends of ecological parameters on a regional level, followed by overlaying LULC data to assess the variations in average values, trends, and numerical ranges of ecological parameters across various LUTs. Ultimately, it was determined that LULC change exerts a substantial influence on ecological parameters, resulting in significant distinctions in regional attributes.
## 3 Results
### Spatio-Temporal Variations of Vegetation Phenology
#### 3.2.2 Temporal Variations  
The spatial distribution of the trends of vegetation phenology in the SRYR from 2001 to 2019 is shown in the Figure 4. The average SOS in the SRYR was 138.6 \(\pm\) 3.6 d (Figure 4a) and showed a significantly advanced trend (\(-\)0.40 d yr\({}^{-1}\), \(p\) < 0.01). A total 25.2% of the SRYR had a significantly advanced SOS (\(p\) < 0.05), which was mainly distributed in the central and eastern SRYR. The average EOS in the region was 287.8 \(\pm\) 2.6 d (Figure 4b) and showed a slightly and insignificantly advanced trend (\(-\)0.08 d yr\({}^{-1}\), \(p\) > 0.05). The average LOS in the SRYR was 149.2 \(\pm\) 4.5 d (Figure 4c) and showed an insignificantly extended trend (\(+\)0.41 d yr\({}^{-1}\), \(p\) > 0.05). A total 18.0% of the SRYR had a significantly extended LOS (\(p\) < 0.05), which had a similar distribution pattern with that of the significantly advanced SOS. The extended LOS resulted from the advanced SOS in the central and eastern SRYR, which was consistent with the results of [PERSON] et al. (2019). [PERSON] et al. (2019) found a significantly advanced SOS, delayed EOS and extended LOS in the Qinghai-Tibet Plateau. However, we did not find significant trends for EOS and LOS in the SRYR.  
Figure 3: Spatial distribution of average vegetation: (**a**) SOS, (**b**) EOS, (**c**) LOS and (**d**) POS in the SRYR from 2001 to 2019. The frequency distribution of vegetation phenology is shown in the lower left corner.  
The average POS was 209.0 \(\pm\) 3.3 d (Figure 4d) and showed a significantly advanced trend (\(-\)0.39 d yr\({}^{-1}\), \(p\) < 0.05). A total 19.1% of the pixels had a significantly advanced POS, while the proportion of regions in which the POS was significantly delayed (\(p\) < 0.05) was less than 1.0%. The regions with larger advanced rates (slope\({}_{\text{POS}}\) < 1.0 d yr\({}^{-1}\)) were mainly distributed in the north, southeast and northwest of the SRYR.
# A Hybrid Encryption Scheme for Quantum Secure Video Conferencing Combined with Blockchain
## 4 Our Construction
### Hybrid Encryption  
According to the secret level of the video conference content, the system designs two data encryption schemes: one is the classical key encryption scheme and the other is the quantum key encryption scheme. The two schemes can be switched without affecting the operation of the video services. This configuration is an excellent business redundancy mechanism of quantum secure communication in a video conference system:  
1. The secret level of the video conference content is low, and the business data adopt a classical key encryption scheme.
2. The secret level of the video conference content is high, and the business data adopt the quantum key encryption scheme.
# Research Progress and Applications of 2D Antimonene
## 2 Theoretical Research and Experimental Methods
### Epitaxial Growth
#### 2.4.2 Preparation of Single-Layer Antimonene
Compared with other methods for the preparation of antimonene, molecular beam epitaxy can control the thickness the atomic level, that is, it can optimize the experimental conditions by precisely controlling the experimental parameters and observing the growth process in real time, and prepare single-layer antimonene. Compared with the mechanical exfoliation method, it has a high repeatability rate, and compared with the liquid exfoliation method, contamination from the solvents can be avoided, but its equipment is too expensive.
# Optimizing Geospatial Data for ML/CV Applications:
## 2 Materials
### Data Sources  
LP-Portal, a service provided by Lehmann+Partner Polska Sp. z o.o., supplies road data for road administrators in approximately 100 Polish counties. Data are collected using vehicles equipped with measurement devices. These include tools such as photoregistration systems, GPS/INS positioning systems, and laser measurement devices [50]. The data are publicly available online on LP-Portal county websites [51]. In the project, a list of roads from selected counties was obtained along with their nodes, providing the foundational geometry for road networks.  
ULDK is a cadastral parcel localization service from the Polish Head Office of Geodesy and Cartography (Glowny Urzad Geodezji i Kartografii, GUGiK). The service enables spatial localization of specified cadastral parcels [52]. ULDK was used to identify corresponding cadastral parcels for each road node from LP-Portal. The service returns the parcel geometry in 'Well-Known Binary' (WKB) format, which was converted into geometric objects using 'Shapely'.  
Geoportal is an internet application that offers access to reliable spatial data from Poland's National Spatial Data Infrastructure (Krajowa Infrastruktura Informacji Przestrztennej). It provides free, high-quality, and up-to-date spatial information from official registers [27]. In the project, Geoportal's WMS was utilized to access orthoimagery. This was possible by using endpoints providing information on the available orthoimagery for different regions and orthoimagery services allowing to obtain standard-resolution (25 cm per pixel) or high-resolution (5 or 10 cm per pixel) aerial imagery corresponding to the road segments and parcels of interest [53].
# Robust Template-Based Watermarking for DIBR 3D Images
## 3 Proposed Method  
### Main Idea of the Proposed Method  
The overall flow of watermark embedding/extraction is shown in Figure 4. As shown, the proposed watermarking system consists of a template and message watermark. This section describes the characteristics and roles of the template and message.  
The DIBR watermarking system must be robust to both DIBR and geometric attacks, as shown in Figure 1. The proposed method inserts a template into a curvelet domain robust against DIBR and geometric distortions. The inserted template enables restoring the image from geometric distortion without being destroyed by DIBR. Geometric distortion can be restored by inserting the template in peak point form and matching detected peaks with ground-truth positions, which can be obtained from the template key in the detection step.  
Figure 3: Curvelet in the frequency and spatial domain. (**a**) Curvelet tiling of the frequency domain; (**b–d**) Curvelets for various scales and directions in the spatial domain. Curvelets are drawn on \(k_{1}=w/2\) and \(k_{2}=h/2\).  
However, although the peak matching method can recover global geometric distortion that occurs across the entire image, DIBR distortion cannot be recovered because it is treated as horizontal error. In addition, the peak point form template cannot insert messages. To address these problems, we designed an invariant message watermarking technique against DIBR, where DIBR deformations that cannot be restored by the template are handled by the message watermark. Message watermarks without templates are vulnerable to geometric attacks, but combining the advantages of the template and message watermark allows a robust DIBR watermarking system.  
In summary, the template and message in the proposed watermarking system complement each other's weaknesses. The curvelet with robustness to DIBR is utilized as a template to restore images from geometric attacks. The message watermark inserted in the 1D-DCT domain resolves the unrecovered damage caused by DIBR. The message watermark itself is not robust to geometric attacks, but images that have suffered geometric attacks can be restored using templates. The roles of templates and message watermarks are summarized in Table 3.
# Software Fault Localization Based on SALSA Algorithm
## 3 Proposed Approach
### Data Pre-Processing
#### 3.1.3 Obtain the Root Set  
In the SALSA algorithm, the root set refers to the initial collection of web pages that are highly relevant to the user's query request. These web pages are considered highly trustworthy and are usually carefully selected based on certain criteria or prior knowledge. The selection of the root set directly affects the trust propagation and node evaluation results across the entire network. Therefore, when choosing the root set, various factors need to be carefully considered to ensure that the selected web pages have sufficient representativeness and credibility. In this paper, the concept of a root set is used, which refers to a collection of statements that are highly related to the fault. Considering that a program statement is more suspicious if it is executed more frequently in failed tests and less frequently in passing tests, this paper analyzes the spectrum to count all program statements in failed test cases and eliminates those that are executed frequently in passing test cases. Ultimately, a set of program statements with high suspiciousness is obtained, known as the root set (RS). Taking the spectrum from Table 1 as an example, RS1 is obtained, which includes e3, e4, e5, and e7.
# Validating Precise Orbit Determination from Satellite-Borne GPS Data of Haiyang-2D
## 3 Results and Discussion
### Orbit Determination Strategies and Analysis of Accuracy  
HY-2D satellite-borne GPS data are released by NSOAS with a sampling interval of 1 s. The precise ephemeris, precise clock offsets, DCB correction, etc., required for POD are provided by the Centre for Orbit Determination in Europe (CODE). The accuracy validation of orbits is carried out using the SLR data provided by the ILRS and precise ephemeris provided by the International GNSS Service (IGS). Detailed information about the data used in the article is shown in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**DOY** & **MP1 (m)** & **MP2 (m)** & **O/slps** & **Completeness Rate** & **Utilization Rate** \\ \hline
262 & 0.39 & 0.27 & 45 & 99.95\% & 99.33\% \\
263 & 0.35 & 0.21 & 48 & 99.62\% & 98.02\% \\
264 & 0.31 & 0.22 & 54 & 99.95\% & 98.82\% \\
265 & 0.33 & 0.23 & 53 & 84.80\% & 84.43\% \\
266 & 0.36 & 0.20 & 84 & 99.94\% & 99.26\% \\
267 & 0.30 & 0.22 & 30 & 99.95\% & 98.70\% \\
268 & 0.40 & 0.24 & 42 & 99.88\% & 98.68\% \\ \hline \end{tabular}
\end{table}
Table 1: HY-2D data quality assessment.  
Figure 1: Multipath effects of HY-2D and G03 on DOY 266 in 2021. (**a,b**) MP1; (**c,d**) MP2.
## 4 Conclusions  
This paper presented the developments in the research and implementation of DLR technologies. The detection capabilities of the DLR system have been improved by increasing the PRF of laser ranging and reducing background light noise and dark noise in the detector. For the nanosecond laser with an average power of 60 W, a PRF of 200 Hz, and a wavelength of 532 nm, the measurement performance was equivalent to an RCS of 0.26 m\({}^{2}\) at a distance of 1000 km. Meanwhile, using a 532 nm pulse-burst picosecond laser with an average power of 20 W and a PRF of 1 kHz, debris measurements was achievable up to 1726.8 km (with an RCS of 0.91 m\({}^{2}\), corresponding to an RCS of 0.1 m\({}^{2}\) at a distance of 1000 km). It was demonstrated that the picosecond laser outperforms the nanosecond laser in terms of ranging precision and capabilities, and it is also expected to be a new direction of DLR development. Owing to the ultra-high repetition rate of SLR technology, an increase in the single-pulse energy of the laser effectively increases the average number of echoes per unit time. Furthermore, the development of laser technology with a PRF of 100 to 500 kHz and a transceiver alternating mode will provide a new way of making ranging measurements.  
[PERSON] designed the technology of the debris laser ranging (DLR) system; [PERSON] was in charge of the laser system and analyzed the characteristics of the pico-laser; [PERSON] updated the laser system and observations; [PERSON] and [PERSON] performed the experiments; [PERSON] designed the telescope array of laser ranging; [PERSON] and [PERSON] designed the technology of the DLR system; [PERSON] and [PERSON] analyzed the data; [PERSON] and [PERSON] wrote the draft of the paper; and [PERSON] and [PERSON] modified the paper. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (12003056 and 11903066), Natural Science Foundation of Shanghai (20 ZR1467500), and the Key Research Program of the Chinese Academy of Sciences (ZDRW-KT-2019-3-6).  
Not applicable.  
The authors thank the Space Track Organization (www.space-track.org (accessed on 23 September 2021)) for making available the two-line elements and information of the cataloged objects; Institute of Applied Electronics of CAEP and Beijing University of Technology for providing the laser system; and East China Normal University and Shanghai Institute of Microsystem and Information Technology of CAS for providing the laser detector.  
The authors declare no conflict of interest.  
Figure 21: Results of the measured range (**left**) and precision (**right**) vs. the RCS obtained using the pulse-burst picosecond laser.
# Uncertainties and Perspectives on Forest Height Estimates by Sentinel-1 Interferometry
## 3 Results and Discussion  
To verify if _dh_ values associated with tree heights could be reasonably estimated independently from phase unwrapping, HOA was related to \(B\) according to the above-mentioned equations, namely HOA = 2\(\pi\cdot\omega\) and Equation (1). \(B\) values were progressively changed to generate graphs of Figure 2.  
With reference to Figure 2, one can deduce that a baseline value lower than about 120 m can be used to ensure that forest height estimates can be given. In fact, forests around the world rarely show tree heights higher than 100 m. If focusing on temperate forests where maximum tree height is 65 m, baseline values lower than about 270 m can be used, ensuring to remain within HOA.