Reflectance Ratio Research Articles

Honeycomb Cell Structures Formed in Drop-Casting CNT Films for Highly Efficient Solar Absorber Applications.

This study investigates the process of using multi-walled carbon nanotube (MWCNT) coatings to enhance lamp heating temperatures for solar thermal absorption applications. The primary focus is studying the effects of the self-organized honeycomb structures of CNTs formed on silicon substrates on different cell area ratios (CARs). The drop-casting process was used to develop honeycomb-structured MWCNT-coated absorbers with varying CAR values ranging from ~60% to 17%. The optical properties were investigated within the visible (400-800 nm) and near-infrared (934-1651 nm) wavelength ranges. Although fully coated MWCNT absorbers showed the lowest reflectance, honeycomb structures with a ~17% CAR achieved high-temperature absorption. These structures maintained 8.4% reflectance at 550 nm, but their infrared reflection dramatically increased to 80.5% at 1321 nm. The solar thermal performance was assessed throughout a range of irradiance intensities, from 0.04 W/cm2 to 0.39 W/cm2. The honeycomb structure with a ~17% CAR value consistently performed better than the other structures by reaching the highest absorption temperatures (ranging from 52.5 °C to 285.5 °C) across all measured intensities. A direct correlation was observed between the reflection ratio (visible: 550 nm/infrared: 1321 nm) and the temperature absorption efficiency, where lower reflection ratios were associated with higher temperature absorption. This study highlights the significant potential for the large-scale production of cost-effective solar thermal absorbers through the application of optimized honeycomb-structured absorbers coated with MWCNTs. These contributions enhance solar energy efficiency for applications in water heating and purification, thereby promoting sustainable development.

Influence of Conductive Filler Types on the Ratio of Reflection and Absorption Properties in Cement-Based EMI Shielding Composites

The growing importance of electromagnetic interference (EMI) shielding composites in civil engineering has garnered increasing attention. Conductive cement-based composites, incorporating various conductive fillers, such as carbon nanotubes (CNTs), carbon fibers (CFs), and graphene nanoplatelets (GNPs), provide effective solutions due to their high electrical conductivity. While previous studies have primarily focused on improving the overall shielding effectiveness, this research emphasizes balancing the reflection and absorption properties. The experimental results demonstrate an EMI shielding performance exceeding 50 dB, revealing that filler size (nano, micro, or macro) and shape (platelet or fiber) significantly influence both reflection and absorption characteristics. Based on a comprehensive evaluation of the shielding properties, this study highlights the need to consider factors such as reflection versus absorption losses and filler shape or type when optimizing filler content to develop effective cement-based EMI shielding composites.

Satellite algorithms for retrieving dissolved organic carbon concentrations in Chinese lakes

Water quality and the carbon cycle in lakes are strongly related to the concentration of dissolved organic carbon (DOC). Several regional algorithms have been proposed to remotely retrieve lake DOC concentration at a regional scale, but further efforts are needed to reliably retrieve DOC concentration over a large area. Based on bio-optical measurements from 55 lakes across China, this study investigates feasible satellite algorithms for retrieving DOC concentrations from OLCI/Sentinel-3 imagery. The results revealed that the bio-optical characteristics of DOC were different in freshwater and saline lakes. Compared to saline lakes, freshwater lakes had lower DOC concentrations (9.89 ± 3.97 mg/L vs. 32.97 ± 42.07 mg/L) but similar levels of colored dissolved organic matter as indicated by its absorption coefficient at 280 nm (aCDOM(280), 12.8 ± 6.94 1/m vs. 17.15 ± 22.97 1/m). Moreover, DOC concentrations in freshwater lakes were exponentially related to aCDOM(280) (r = 0.74) and linearly correlated with red-to-green reflectance ratios. However, DOC concentration in saline lakes was linearly related to aCDOM(280) (r = 0.93) and exponentially correlated with red-to-blue reflectance ratios. Then, although we discriminated freshwater and saline lakes with a conductivity threshold of 2000 μs/cm, the three commonly used linear regression methods for estimating DOC concentrations still obtained mean absolute percent difference (MAPD) of 55.68–66.44 %. Alternatively, we developed a hybrid machine learning algorithm (MAPD = 18.16 %), that used water reflectance and lake/basin properties to model DOC concentrations in freshwater and saline lakes, respectively. Satellite monitoring of 370 large lakes (> 20 km2) showed that DOC concentration was high in the northwest and low in the southeast of China. This study has implications for dynamic monitoring of DOC concentrations in lakes using satellite imagery.

Virtual Reflection Height of Nighttime Equatorial Ionosphere Estimated With Low‐Frequency Magnetic Sferics Measured in Malacca

AbstractThe return stroke of cloud‐to‐ground (CG) lightning is an impulsive radiator of very low‐frequency/low‐frequency (VLF/LF) electromagnetic signals allowing for the remote sensing of lower ionosphere over large spatial coverage. In this study, we examined the LF magnetic fields measured in Malacca, Malaysia, to probe reflection heights of the lower ionosphere near the equator on three different nights in 2021. The results show that the virtual ionospheric height at nighttime typically ranged from 82.0 to 90.0 km, with a mean value of 85.3 km. Our measurements also revealed significant variations in the virtual ionospheric height across different regions over a spatial scale of about 800 km. The maximum height difference was about 5.0 km. Moreover, the fluctuation characteristics are observed in both estimated ionospheric height and calculated peak reflection ratio during similar periods. This fluctuation may be related to atmospheric gravity waves in the nighttime ionosphere. In addition, we compared the virtual ionospheric height estimated from CG strokes of different polarities, and the results showed that the virtual reflection height for positive CG strokes is lower than that for negative ones.

Corneal stromal changes following simple limbal epithelial transplantation on Scheimpflug densitometry: Early results.

Chemical injury to eyes causes limbal stem cell deficiency (LSCD), which leads to conjunctival epithelium and underlying stromal changes. Simple limbal epithelial transplant helps to restore corneal epithelium and corneal stromal clarity. These changes are documented in this prospective eye study. To report the changes in epithelial/stromal (E/S) reflectivity ratio and corneal stromal densitometry following simple limbal epithelial transplantation (SLET) in patients with unilateral chemical burn-induced LSCD. It is a prospective imaging study of cornea before and after SLET. Corneal densitometry with Pentacam and epithelial and stromal reflectivity on anterior segment optical coherence tomography were analyzed for five patients (n = 5 eyes), who underwent autologous SLET for unilateral chemical burn-induced LSCD. Mann-Whitney U-test and Pearson correlation. A significant improvement in E/S reflectivity was noted at 1 month (P < 0.05) after SLET, and this was maintained until the end of 6 months. The densitometry measurements decreased in the entire cornea at every level, that is, anterior, central, and posterior cornea. However, the values did not normalize till the last follow-up at 6 months. A trend of normal corneal epithelization exists in eyes undergoing SLET. Densitometry at all the levels, the anterior, central, and posterior cornea, also decreases after SLET. SLET improves visual outcomes in LSCD eyes not only by epithelization but also by reducing stromal scarring.

Study on Thermal Reflection Characteristics of Composite Inorganic Coatings

This study examined the thermal reflective properties of composite inorganic coatings applied to various wall types. It evaluated the influence of these coatings on the thermal insulation and reflectivity of the walls. The findings indicate that coating application markedly enhances a wall’s thermal insulation capabilities and increases its heat flux reflection ratio. These results offer crucial theoretical backing and practical guidance for the future use of coating technologies in construction. By refining the coating formulations and application processes, the thermal insulation properties of walls can be further enhanced, thus making a significant contribution to building energy efficiency and environmental protection. Consequently, this research provides essential references and insights for advancing coating technology in the construction industry.

Thickened photoreceptor outer segment layer in children with hyperopic anisometropic amblyopia.

To quantitatively investigate the reflectivity and structure of the outer retinal layers in children with hyperopic anisometropic amblyopia by using swept-source optical coherence tomography (SS-OCT). Seventy-eight patients with amblyopia and 64 age-matched children with normal vision were included in this study. All participants underwent SS-OCT and detailed ophthalmic examinations. Longitudinal reflectance profile measurements were measured using Image J. The reflectivity of outer retinal layers was measured at the three selected positions: subfovea, 1 mm nasal to the fovea, and 1 mm temporal to the fovea. The reflectivity ratios were calculated by outer retinal layers divided by the nuclear layer (ONL) for normalization. Photoreceptor outer segment layer thickness was also measured. The results were compared between the amblyopia and normal controls. The possible effects of age, sex, and axial length on results were adjusted by generalized estimating equations. Photoreceptor outer segment layer thickness was significantly greater in amblyopic eyes than in normal control eyes at all three regions (18.41 ± 1.83 vs. 16.84 ± 1.39, P < 0.001 at the fovea; 14.78 ± 1.34 vs. 14.19 ± 1.40, P = 0.030 at 1 mm nasal to the foveal; 14.92 ± 1.48 vs. 14.41 ± 1.32, P = 0.049 at 1 mm temporal to the fovea). The reflectivity ratio of outer segment/ONL was higher only at 1 mm nasal to the fovea (2.94 ± 0.61 vs. 2.70 ± 0.42, P = 0.02). Subfoveal OS thickness was positively correlated with choroidal thickness (r = 0.248, P = 0.018) but was not correlated with spherical equivalent, age, axial length, or logMAR visual acuity. Quantitative measurement of SS-OCT images revealed greater photoreceptor outer segments in both eyes of children with amblyopia than in normal control eyes. A thicker OS thickness is somehow related to amblyopia, and this may be a new useful diagnostic parameter for amblyopia.

Transport of the Hunga volcanic aerosols inferred from Himawari-8/9 limb measurements

Abstract. The Hunga volcano (21.545° S, 178.393° E; also known as Hunga Tonga-Hunga Ha′apai) erupted on 15 January 2022, producing copious amounts of aerosols that reached high into the stratosphere, exceeding 30 km and settling into layers a few kilometres deep between 22 and 28 km. The Advanced Himawari Imager (AHI) on board the geostationary Himawari-8/9 platform at 140.7° E was able to monitor the eruption at 10 min intervals and 0.25 to 4 km2 spatial resolution within 16 spectral channels ranging from visible to infrared wavelengths and over a latitude–longitude field of view of ∼ ±75°. Here a new use of these data is proposed where the limb region of the field of view is exploited to detect aerosol layers extending vertically into the atmosphere. The analyses provide vertical profiles of scattered visible light and are compared to CALIOP space lidar measurements. Hunga aerosols are detected using the ratio of near-infrared reflectances at 1.61 and 2.25 µmm in the western limb from 22 January and in the eastern limb from 31 January 2022 up until the present time (December 2023). Between January and April 2022, the average zonal velocity is estimated to be ∼ −25 m s−1 (westwards) and the meridional velocity to be ∼ 0.2 m s−1 (northwards). The latitudinal spread is characterized by a gradual northerly movement of the main layer situated between 22 and 28 km in the first 60 d, and stagnation or slight southerly spread thereafter. There is a shallow maximum of the lower stratospheric aerosol between 10 and 20° S, and the aerosol loading during 2023 is elevated compared with the 3 months prior to the eruption. The Southern Hemisphere (0–30° S) tropical lower stratospheric aerosol e-folding time is estimated to be ∼ 12 months, but the decay is not uniform and has high variability. The current methodology does not provide quantitative estimates of the amount or type of aerosol, but based on the spectral properties of water and ice clouds the analysis suggests there is a strong liquid water content in the aerosol layers.

Enhancing Machine Learning Performance in Estimating CDOM Absorption Coefficient via Data Resampling

Chromophoric dissolved organic matter (CDOM) is a mixture of various types of organic matter and a useful parameter for monitoring complex inland surface waters. Remote sensing has been widely utilized to detect CDOM in various studies; however, in many cases, the dataset is relatively imbalanced in a single region. To address these concerns, data were acquired from hyperspectral images, field reflection spectra, and field monitoring data, and the imbalance problem was solved using a synthetic minority oversampling technique (SMOTE). Using the on-site reflectance ratio of the hyperspectral images, the input variables Rrs (452/497), Rrs (497/580), Rrs (497/618), and Rrs (684/618), which had the highest correlation with the CDOM absorption coefficient aCDOM (355), were extracted. Random forest and light gradient boosting machine algorithms were applied to create a CDOM prediction algorithm via machine learning, and to apply SMOTE, low-concentration and high-concentration datasets of CDOM were distinguished by 5 m−1. The training and testing datasets were distinguished at a 75%:25% ratio at low and high concentrations, and SMOTE was applied to generate synthetic data based on the training dataset, which is a sub-dataset of the original dataset. Datasets using SMOTE resulted in an overall improvement in the algorithmic accuracy of the training and test step. The random forest model was selected as the optimal model for CDOM prediction. In the best-case scenario of the random forest model, the SMOTE algorithm showed superior performance, with testing R2, absolute error (MAE), and root mean square error (RMSE) values of 0.838, 0.566, and 0.777 m−1, respectively, compared to the original algorithm’s test values of 0.722, 0.493, and 0.802 m−1. This study is anticipated to resolve imbalance problems using SMOTE when predicting remote sensing-based CDOM. It is expected to produce and implement a machine learning model with improved reliable performance.

Multifrequency radar observations of marine clouds during the EPCAPE campaign

Abstract. The Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) was a year-round campaign conducted by the US Department of Energy at the Scripps Institution of Oceanography in La Jolla, CA, USA, with a focus on characterizing atmospheric processes at a coastal location. The ground-based prototype of a new Ka-, W-, and G-band (35.75, 94.88, and 238.8 GHz) profiling atmospheric radar, named CloudCube, which was developed at the Jet Propulsion Laboratory, took part in the experiment during 6 weeks in March and April 2023. This article describes the unique data sets that were obtained during the field campaign from a variety of marine clouds and light precipitation. These are, to the best of the authors' knowledge, the first observations of atmospheric clouds using simultaneous multifrequency measurements including 238.8 GHz. These data sets therefore provide an exceptional opportunity to study and analyze hydrometeors with diameters in the millimeter- and submillimeter size range that can be used to better understand cloud and precipitation structure, formation, and evolution. The data sets referenced in this article are intended to provide a complete, extensive, and high-quality collection of G-band data in the form of Doppler spectra and Doppler moments. In addition, Ka-band and W-band reflectivity and Ka-, W-, and G-band reflectivity ratio profiles are included for several cases of interest on 6 different days. The data sets can be found at https://doi.org/10.5281/zenodo.10076227 (Socuellamos et al., 2024).

Construction of Rules for Recognizing Landslides Along Highways Induced By Rainfall

After the "7-20" concentrated rainfall, many landslides occurred along the highways in Jiaozuo City, which seriously threatened the transportation safety and brought serious economic losses to the government and the residents along the highways. In order to investigate the development pattern and distribution characteristics of landslides along highways under extreme weather, we took Jiaozuo City Highway as the research object, based on the Sentinel-2 remote sensing data, and on the basis of analyzing the spectral characteristics of landslide hazards, we used the band ratio method to establish the identification rules of loess landslides along highways; based on the topography, geology, human impacts, and meteorological and hydrological selected 11 impact factors, and used geoprospectors to investigate the The driving factors of landslides. The following conclusions and understandings were obtained: (1) a total of 256 landslides along the highway in Jiaozuo City were identified, and the overall identification accuracy of 69.9% was obtained through visual interpretation and on-site research; (2) the ratio of the surface true reflectance of red and green light fused with the slope (&gt;15°) can be used to carry out the identification of landslides in large-scale post-disaster situations; (3) the human activities and topography have a greater impact on landslide development; (4) the identification rule has a greater impact on the development of landslides with similar geological backgrounds. rule is useful for the identification and prevention of landslides along highways in low-hill loess-covered areas with similar geologic backgrounds.

Design and operation of a load-tolerant ICRH system in Experimental Advanced Superconducting Tokamak

Ion Cyclotron Resonance Heating (ICRH) has been a dependable tool for sturdy plasma heating with high RF power of several megawatts. However, a sudden increase in the reflected power during ICRH heating experiments is a problem that should be solved for future fusion experimental devices. To solve this issue, a load tolerant matching network has been designed for the ICRH system in EAST. The matching network includes a 3-stub tuner impedance matching system with conjugate-T structure, 30 Ω to 50 Ω transmission line and center grounded antenna strap. By maintaining a low reflection ratio in the network for a wide range of resistance, this matching network can allow sturdy high-power operations without fast impedance matching in EAST. In our matching network, the two arms of a conjugate-T are designed to have a λ/2 length difference which could mitigate current imbalance and antenna poloidal phasing outside of the control problem. The T-point corresponds to the maximum point of the standing wave voltage, which could greatly improve the input impedance of the antenna.

Characterization of central-involved diabetic macular edema using OCT and OCTA.

To characterize the occurrence of diabetic macular edema and the presence of abnormal retinal fluid accumulation in nonproliferative diabetic retinopathy (NPDR). In this two-year prospective study, a total of 122 eyes with diabetes type 2 underwent optical coherence tomography (OCT) and OCT-Angiography in association with OCT-Fluid imaging, a novel algorithm of OCT analysis allowing quantification of abnormal accumulation of fluid in the retina through low optical reflectivity ratios (LOR). Early Treatment Diabetic Retinopathy Study (ETDRS) grading for diabetic retinopathy (DR) severity assessment was performed using 7-field color fundus photography. Best corrected visual acuity was also recorded. During the 2-year follow-up, 23 eyes (19%) developed central-involved diabetic macular edema (CI-DME) and 2 eyes (2%) developed clinically significant macular edema (CSME). In the two-year period of the study, eyes that developed CI-DME showed a progressive increase in central retinal thickness (CRT) (β = 7.7 ± 2.1 µm/year, p < 0.001) and in LOR values (β = 0.009 ± 0.004 ratio/year, p = 0.027). The increase in CRT and abnormal retinal fluid, represented by increased LOR ratios, are associated with increased retinal perfusion in the deep capillary plexus (DCP) (skeletonized vessel density, p = 0.039). In contrast, the eyes with CSME showed decreased retinal perfusion and abnormal fluid located in the outer layers of the retina. CI-DME and CSME appear to represent different entities. Eyes with CI-DME show increases in abnormal retinal fluid associated with increased retinal vascular perfusion in the DCP. Eyes with CSME are apparently associated with decreased retinal vascular perfusion in the DCP and abnormal fluid in the outer retina.

Hailstorm events in the Central Andes of Peru: insights from historical data and radar microphysics

Abstract. Hailstorms, while fascinating from a meteorological perspective, pose significant risks to communities, agriculture, and infrastructure. In regions such as the Central Andes of Peru, the characteristics and frequency of these extreme weather events remain largely uncharted. This study fills this gap by investigating the historical frequency and vertical structure of hailstorms in this region. We analyzed historical hailstorm records dating back to 1958 alongside 4 years of observations (2017–2021) from the Parsivel2 disdrometer and a cloud-profiling radar MIRA35c. Our findings indicate a trend of decreasing hail frequency (−0.5 events per decade). However, the p value of 0.07 suggests the need for further investigation, particularly in relation to environmental changes and reporting methods. The results show that hailstorms predominantly occur during the austral summer months, with peak frequency in December, and are most common during the afternoon and early evening hours. The analysis of radar variables such as reflectivity, radial velocity, spectral width, and linear depolarization ratio (LDR) reveals distinct vertical profiles for hail events. Two case studies highlight the diversity in the radar measurements of hailstorms, underscoring the complexity of accurate hail detection. This study suggests the need for refining the Parsivel2 algorithm and further understanding its classification of hydrometeors. Additionally, the limitations of conventional radar variables for hail detection are discussed, recommending the use of LDR and Doppler spectrum analysis for future research. Our findings lay the groundwork for the development of more efficient hail detection algorithms and improved understanding of hailstorms in the Central Andes of Peru.

Insights into Canopy Escape Ratio from Canopy Structures: Correlations Uncovered through Sentinel-2 and Field Observation

This study explores the quantitative relationship between canopy structure and the canopy escape ratio (fesc), measured as the ratio of near-infrared reflectance of vegetation (NIRv) to the fraction of absorbed photosynthetically active radiation (fAPAR). We analyzed the correlation between fesc and key indicators of canopy structure—specifically, leaf area index (LAI) and clumping index (CI)—utilizing both Sentinel-2 satellite data and in situ observations. Our analysis revealed a moderate correlation between fesc and LAI, evidenced by an R2 value of 0.37 for satellite-derived LAI, which contrasts with the lower correlation (R2 of 0.15) observed with field-measured LAI. Conversely, the relationship between fesc and CI proved to be significantly weaker (R2 &lt; 0.1), indicating minimal interaction between foliage distribution and light escape at the canopy level. This disparity in correlation strength was further evidenced in time series analysis, which showed little phenological variation in fesc compared to LAI. Our findings elucidate the complexities of estimating fesc based on the NIRv to fAPAR ratio and underscore the need for advanced methodologies in future research to enhance the accuracy of canopy escape models.

High transmission of circularly polarized light and circular dichroism with all-dielectric metamaterial

The optical chirality of metamaterials gives birth to distinct responses of left circularly polarized (LCP) and right circularly polarized (RCP) light, leading to asymmetric transmission and circular dichroism (CD) of circularly polarized light. In this work, meta-atom structure composed of square and semicircular combinations were designed, which exhibits extreme high ratio of transmission, reflection and CD values in blue light range. In compare to other reported structures, the structure composed of semicircular and square combinations can achieve better asymmetric transmission. At the wavelength of 460 nm, the incident LCP light can be mostly converted to RCP light, and the incident RCP light can be almost completely reflected. Furthermore, the geometric phase can be controlled by designing the orientation angle of the meta-atom, and the metamaterial can function under any linear or circular polarization and achieving the regulation of the light field. The designed metamaterial provides promising insights into the high CD and possible applications in optical integrated devices, such as anomalously refracted, focusing, and holograms, etc.

Validation of a Novel Noninvasive Technology to Estimate Blood Oxygen Saturation Using Green Light: Observational Study

Background Pulse oximeters work within the red-infrared wavelengths. Therefore, these oximeters produce erratic results in dark-skinned subjects and in subjects with cold extremities. Pulse oximetry is routinely performed in patients with fever; however, an elevation in body temperature decreases the affinity of hemoglobin for oxygen, causing a drop in oxygen saturation or oxyhemoglobin concentrations. Objective We aimed to determine whether our new investigational device, the Shani device or SH1 (US Patent 11191460), detects a drop in oxygen saturation or a decrease in oxyhemoglobin concentrations. Methods An observational study (phase 1) was performed in two separate groups to validate measurements of hemoglobin and oxygen concentrations, including 39 participants recruited among current university students and staff aged 20-40 years. All volunteers completed baseline readings using the SH1 device and the commercially available Food and Drug Administration–approved pulse oximeter Masimo. SH1 uses two light-emitting diodes in which the emitted wavelengths match with absorption peaks of oxyhemoglobin (hemoglobin combined with oxygen) and deoxyhemoglobin (hemoglobin without oxygen or reduced hemoglobin). Total hemoglobin was calculated as the sum of oxyhemoglobin and deoxyhemoglobin. Subsequently, 16 subjects completed the “heat jacket study” and the others completed the “blood donation study.” Masimo was consistently used on the finger for comparison. The melanin level was accounted for using the von Luschan skin color scale (VLS) and a specifically designed algorithm. We here focus on the results of the heat jacket study, in which the subject wore a double-layered heated jacket and pair of trousers including a network of polythene tubules along with an inlet and outlet. Warm water was circulated to increase the body temperature by 0.5-0.8 °C above the baseline body temperature. We expected a slight drop in oxyhemoglobin concentrations in the heating phase at the tissue level. Results The mean age of the participants was 24.1 (SD 0.8) years. The skin tone varied from 12 to 36 on the VLS, representing a uniform distribution with one-third of the participants having fair skin, brown skin, and dark skin, respectively. Using a specific algorithm and software, the reflection ratio for oxyhemoglobin was displayed on the screen of the device along with direct hemoglobin values. The SH1 device picked up more minor changes in oxyhemoglobin levels after a change in body temperature compared to the pulse oximeter, with a maximum drop in oxyhemoglobin concentration detected of 6.5% and 2.54%, respectively. Conclusions Our new investigational device SH1 measures oxygen saturation at the tissue level by reflectance spectroscopy using green wavelengths. This device fared well regardless of skin color. This device can thus eliminate racial disparity in these key biomarker assessments. Moreover, since the light is shone on the wrist, SH1 can be readily miniaturized into a wearable device.

Phase Error Reduction for a Structured-Light 3D System Based on a Texture-Modulated Reprojection Method.

Fringe projection profilometry (FPP), with benefits such as high precision and a large depth of field, is a popular 3D optical measurement method widely used in precision reconstruction scenarios. However, the pixel brightness at reflective edges does not satisfy the conditions of the ideal pixel-wise phase-shifting model due to the influence of scene texture and system defocus, resulting in severe phase errors. To address this problem, we theoretically analyze the non-pixel-wise phase propagation model for texture edges and propose a reprojection strategy based on scene texture modulation. The strategy first obtains the reprojection weight mask by projecting typical FPP patterns and calculating the scene texture reflection ratio, then reprojects stripe patterns modulated by the weight mask to eliminate texture edge effects, and finally fuses coarse and refined phase maps to generate an accurate phase map. We validated the proposed method on various texture scenes, including a smooth plane, depth surface, and curved surface. Experimental results show that the root mean square error (RMSE) of the phase at the texture edge decreased by 53.32%, proving the effectiveness of the reprojection strategy in eliminating depth errors at texture edges.

Evaluating the impact of pavement reflectance and aspect ratio on thermal conditions in a scale model of a street canyon: introducing PAVSCAM

Evaluating the impact of pavement reflectance and aspect ratio on thermal conditions in a scale model of a street canyon: introducing PAVSCAM

Improving river medium–high flow estimation by CM Hierarchical Classification (CMHC) method using Sentinel-2 imagery

River discharge monitoring is one of the most important parts of water resources management. However, due to hydrological stations' high operating and maintenance costs, discharge monitoring data has gradually become scarce. Remote sensing technology has great potential to supplement observations in this field. The close relationship between the reflectance ratio of dry (C) and wet (M) pixels around the river in the near-infrared (NIR) band and river discharge has been effectively proved, and many CM-based methods have also achieved good results, but often underestimate medium–high flow in rivers. However, medium–high flow usually occurs during the rainy season or flood-prone periods, and their underestimation not only affects the risk assessment of possible or already occurred floods but may also cause damage to people's lives, property, and social assets. To improve this phenomenon, we proposed a new CM method called CM Hierarchical Classification (CMHC) based on the Sentinel-2 dataset and Google Earth Engine (GEE) cloud platform to monitor the river discharge at different classes and achieve high-precision discharge estimation at medium–high flow. The study was conducted at four stations along the Po River in Italy, where measured discharge data were used to derive the calibration curve and evaluate the performance of the estimated results. The Nash-Sutcliffe efficiency (NS) values for the estimates reached an average of 0.84 and up to 0.89, indicating the excellent performance of the method. Compared with existing methods, our method substantially improves the monitoring accuracy of medium–high flow of the river. Furthermore, additional experiments in the Han River in China also confirmed the applicability of the CMHC method, implying that this method can be used to improve the ability of Sentinel-2 to estimate river discharge, especially for medium–high flow, and provide support for river discharge monitoring on a global scale.