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empirical algorithm for Significant Wave Height Retrieval from Wave Mode Data Provided by the Chinese Satellite Gaofen-3

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REMOTE SENSING 2018年第3期10卷

作者： Wang, He Wang, Jing Yang, Jingsong Ren, Lin Zhu, Jianhua Yuan, Xinzhe Xie, Chunhua State Ocean Adm Natl Ocean Technol Ctr Tianjin 300112 Peoples R China Zhejiang Ocean Univ Marine Acoust & Remote Sensing Lab Zhoushan 316000 Peoples R China State Ocean Adm Inst Oceanog 2 State Key Lab Satellite Ocean Environm Dynam Hangzhou 310012 Zhejiang Peoples R China State Ocean Adm Natl Satellite Ocean Applicat Serv Beijing 100081 Peoples R China

Gaofen-3 (GF-3), the first Chinese civil C-band synthetic aperture radar (SAR), was successfully launched by the China Academy of Space Technology on 10 August 2016. Among its 12 imaging modes, wave mode is designed to monitor the ocean surface waves over the open ocean. An empirical retrieval algorithm of significant wave height (SWH), termed Quad-Polarized C-bandWAVE algorithm for GF-3 wave mode (QPCWAVE_GF3), is developed for quad-polarized SAR measurements from GF-3 in wave mode. QPCWAVE_GF3 model is built using six SAR image and spectrum related parameters. Based on a total of 2576 WaveWatch III (WW3) and GF-3 wave mode match-ups, 12 empirical coefficients of the model are determined for 6 incidence angle modes. The validation of the QPCWAVE_GF3 model is performed through comparisons against independent WW3 modelling hindcasts, and observations from altimeters and buoys from January to October in 2017. The assessment shows a good agreement with root mean square error from 0.5 m to 0.6 m, and scatter index around 20%. In particular, applications of the QPCWAVE_GF3 model in SWH estimation for two storm cases from GF-3 data in wave mode and Quad-Polarization Strip I mode are presented respectively. Results indicate that the proposed algorithm is suitable for SWH estimation from GF-3 wave mode and is promising for other similar data.

关键词： Satellite Gaofen-3 significant wave height empirical algorithm

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INTELLIGENT HEART RATE MONITORING USING empirical algorithm AND DYNAMIC TIME WRAPPING

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INTERNATIONAL JOURNAL OF INNOVATIVE COMPUTING INFORMATION AND CONTROL 2017年第3期13卷 953-966页

作者： Lee, Shih-Hsiung Yang, Chu-Sing Natl Cheng Kung Univ Dept Elect Engn Inst Comp & Commun Engn 1 Univ Rd Tainan 701 Taiwan

This paper lays emphasis on heartbeat monitoring. The polyvinylidene difluoride (PVDF) material is used as the sensor for signal acquisition. There are two crucial subjects in this paper that shall be solved for heart rate calculation. First, the difference in signal amplitude shall be overcome (each analyte has a different heartbeat amplitude or intensity), so that the algorithm can calculate the heart rate effectively. Secondly, the difference in signal frequency or cycle is overcome (each analyte has a different heart rate or cycle), so that the accuracy of calculated heart rate is increased. Finally, the signal acquisition makes noise, which influences the calculation of heartbeat. The signal shall be preprocessed to remove the noise. Added to this, the sensor is placed in different positions, and the algorithm shall identify the signal as heartbeat signal or other signals, which contributes to calculating the heart rate rapidly. Our algorithm can calculate the heart rate effectively when the sensor is placed in different positions (chest and wrist) and overcome the effect of different signal cycle lengths.

关键词： DTW empirical algorithm Heart rate monitoring PVDF

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Adaptation of empirical Methods to Predict the LogD of Triazine Macrocycles

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ACS MEDICINAL CHEMISTRY LETTERS 2023年第10期14卷 1378-1382页

作者： Patterson-Gardner, Casey J. Pavelich, Gretchen M. Cannon, April T. Menke, Alexander J. Simanek, Eric E. Texas Christian Univ Dept Chem & Biochem Ft Worth TX 76129 USA

Octanol/water partition coefficients guide drug design, but algorithms do not always accurately predict these values. For cationic triazine macrocycles that adopt a conserved folded shape in solution, common algorithms fall short. Here, the logD values for 12 macrocycles differing in amino acid choice were predicted and then measured experimentally. On average, AlogP, XlogP, and ChemAxon predictions deviate by 0.9, 2.8, and 3.9 log units, with XlogP overestimating lipophilicity and AlogP and ChemAxon underestimating lipophilicity. Importantly, however, a linear relationship (R (2) > 0.98) exists between the values predicted by AlogP and the experimentally determined logD values, thus enabling more accurate predictions.

关键词： empirical algorithm AlogP logP Triazine Macrocycle Hydrazone Dynamiccovalent chemistry

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Long-term monitoring of total suspended matter concentration in fishponds in the Guangdong-Hong Kong-Macao Greater Bay Area

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ENVIRONMENTAL MONITORING AND ASSESSMENT 2025年第2期197卷 1-24页

作者： Zhou, Tao Yang, Xiankun Cai, Shirong Yang, Qianqian Zhang, Wenxin Li, Zhen Ran, Lishan Guangzhou Univ Sch Geog & Remote Sensing Guangzhou 510006 Peoples R China Guangzhou Univ Rural Nonpoint Source Pollut Comprehens Management Guangzhou 510006 Peoples R China Univ Padua Dept Land Environm Agr & Forestry TESAF Viale Univ 16Agripolis I-35020 Legnaro Italy Univ Hong Kong Dept Geog Pokfulam Rd Hong Kong 999077 Peoples R China

Excessive total suspended matter (TSM) concentrations can exert a considerable impact on the growth of aquatic organisms in fishponds, representing a significant risk to aquaculture health. This study revised existing unified models using empirical data to develop an optimized TSM retrieval model tailored for the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) (R2 = 0.69, RMSE = 7.78 mg/L, and MAPE = 0.23). Employing top-of-atmosphere (TOA) reflectance data from Landsat satellites, accessed via Google Earth Engine (GEE), the refined model facilitated the generation of TSM datasets for fishponds across the GBA from 1986 to 2019. Over these 34 years, there was a marked decline in TSM levels in fishponds, with an approximate 50% reduction in annual average TSM. This decline was particularly notable in the northern, western, and eastern GBA regions, leading to a spatial distribution characterized by higher TSM concentrations in the central and southern regions and lower concentrations in the peripheral regions. Seasonally, TSM levels in GBA fishponds are significantly higher during spring and summer compared to autumn and winter. Regarding natural factors, wind speed shows a significant positive correlation with long-term TSM fluctuations in these environments (p < 0.01). Stocking density, regulated artificially, emerges as a pivotal factor affecting TSM fluctuations. Specifically, TSM concentrations are elevated during periods of high stocking density in the rapid growth phase, and decrease during the mature and harvesting phases when stocking densities are reduced. Furthermore, fishponds situated in impervious areas exhibit significantly higher TSM concentrations compared to those in cropland or forested areas. The economic costs associated with aquaculture drive variations in stocking densities across different land uses within the GBA, contributing to the observed spatial variations in TSM levels. Given the status of the GBA as one of China's most advanced aquacult

关键词： Total suspended matter Fishponds Guangdong-Hong Kong-Macao Greater Bay Area Google Earth Engine empirical algorithm

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Multiple Images Improve Lake CDOM Estimation: Building Better Landsat 8 empirical algorithms across Southern Canada

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REMOTE SENSING 2021年第18期13卷

作者： Koll-Egyed, Talia Cardille, Jeffrey A. Deutsch, Eliza McGill Univ Dept Nat Resource Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Dept Nat Resources Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Bieler Sch Environm Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada Univ Toronto Dept Ecol & Evolutionary Biol 25 Willcocks St Toronto ON M5S 3B2 Canada

Coloured dissolved organic matter (CDOM) is an important water property for lake management. Remote sensing using empirical algorithms has been used to estimate CDOM, with previous studies relying on coordinated field campaigns that coincided with satellite overpass. However, this requirement reduces the maximum possible sample size for model calibration. New satellites and advances in cloud computing platforms offer opportunities to revisit assumptions about methods used for empirical algorithm calibration. Here, we explore the opportunities and limits of using median values of Landsat 8 satellite images across southern Canada to estimate CDOM. We compare models created using an expansive view of satellite image availability with those emphasizing a tight timing between the date of field sampling and the date of satellite overpass. Models trained on median band values from across multiple summer seasons performed better (adjusted R-2 = 0.70, N = 233) than models for which imagery was constrained to a 30-day time window (adjusted R-2 = 0.45). Model fit improved rapidly when incorporating more images, producing a model at a national scale that performed comparably to others found in more limited spatial extents. This research indicated that dense satellite imagery holds new promise for understanding relationships between in situ CDOM and satellite reflectance data across large areas.

关键词： satellite remote sensing Landsat 8 OLI coloured dissolved organic matter Canadian lakes NSERC Canadian Lake Pulse Network empirical algorithm

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Landsat 8 Lake Water Clarity empirical algorithms: Large-Scale Calibration and Validation Using Government and Citizen Science Data from across Canada

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REMOTE SENSING 2021年第7期13卷

作者： Deutsch, Eliza S. Cardille, Jeffrey A. Koll-Egyed, Talia Fortin, Marie-Josee Univ Toronto Dept Ecol & Evolutionary Biol 25 Willcocks St Toronto ON M5S 3B2 Canada McGill Univ Dept Nat Resources Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Bieler Sch Environm Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada

Water clarity has been extensively assessed in Landsat-based remote sensing studies of inland waters, regularly relying on locally calibrated empirical algorithms, and close temporal matching between field data and satellite overpass. As more satellite data and faster data processing systems become readily accessible, new opportunities are emerging to revisit traditional assumptions concerning empirical calibration methodologies. Using Landsat 8 images with large water clarity datasets from southern Canada, we assess: (1) whether clear regional differences in water clarity algorithm coefficients exist and (2) whether model fit can be improved by expanding temporal matching windows. We found that a single global algorithm effectively represents the empirical relationship between in situ Secchi disk depth (SDD) and the Landsat 8 Blue/Red band ratio across diverse lake types in Canada. We also found that the model fit improved significantly when applying a median filter on data from ever-wider time windows between the date of in situ SDD sample and the date of satellite overpass. The median filter effectively removed the outliers that were likely caused by atmospheric artifacts in the available imagery. Our findings open new discussions on the ability of large datasets and temporal averaging methods to better elucidate the true relationships between in situ water clarity and satellite reflectance data.

关键词： Landsat 8 OLI Secchi disk depth water clarity Canadian lakes empirical algorithm

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Remote sensing regression models to estimate water quality indicators in continental waters in North-East Argentina 7

Remote sensing regression models to estimate water quality i...

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2024 Congress of Argentina

作者： Hugo Gauto, Victor Marta Utges, Enid Ivonne Hervot, Elsa Daniela Tenev, Maria Farias, Alejandro Bonansea, Matias Ferral, Anabella UTN FRRe GISTAQ Resistencia Argentina Consejo Nacl Invest Cient & Tecn ICBIA Rio Cuarto Argentina UNC CONAE Inst Mario Gulich Cordoba Argentina

ISBN: (纸本)9798350365948;9798350365931

To ensure water preservation is relevant to constantly monitor water quality. To facilitate this task, remote sensing techniques are applied combining water property measurements and spectral information. Two empirical regression models were developed to estimate chlorophyll-a concentration and turbidity from a water body located in North-East Argentina, in the Metropolitan Area of Gran Resistencia, Chaco Province. The spectral platform used was Sentinel-2 MultiSpectral Instrument, and the physicochemical characterization was achieved by multiple field campaigns where water samples were collected. In the training step several candidate models were compared. Performance metrics (coefficient of determination, R-2, and root mean squared error, RMSE) were calculated and used for the final models selection. The obtained algorithms were linear combinations of spectral bands. Chlorophyll-a algorithm validated performance metrics were R-2 = 0.819 and RMSE = 13.71 mg/m(3). For the turbidity model, R-2 = 0.968 and RMSE = 1.62 NTU. Correlation between physicochemical parameters were asserted and maps were created applying the validated models. A correlation between chlorophyll-a and turbidity was observed. Due this, the spatial distribution in the maps of both parameters followed the same trend.

关键词： remote sensing water quality empirical algorithm chlorophyll-a turbidity Sentinel-2

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Assessment of empirical algorithms for bathymetry extraction using Sentinel-2 data

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INTERNATIONAL JOURNAL OF REMOTE SENSING 2019年第8期40卷 2855-2879页

作者： Casal, Gema Monteys, Xavier Hedley, John Harris, Paul Cahalane, Conor McCarthy, Tim Maynooth Univ Natl Ctr Geocomputat Maynooth Kildare Ireland Geol Survey Ireland Dublin Ireland Numer Opt Ltd Tiverton Devon England Rothamsted Res Sustainable Soil & Grassland Syst Harpenden Devon England Dublin Inst Technol Sch Surveying & Construct Management Dublin Ireland

Bathymetry estimated from optical satellite imagery has been increasingly implemented as an alternative to traditional bathymetric survey techniques. The availability of new sensors such as Sentinel-2 with improved spatial and temporal resolution, in comparison with previous optical sensors, offers innovative capabilities for bathymetry derivation. This study presents an assessment of the fit between satellite data and the underlying models in the most widely used empirical algorithms: the linear band model and the log-transformed band ratio model using Sentinel-2A data. Both models were tested in two study areas of the Irish coast with different morphological and environmental conditions. Results showed that the linear band model fitted better than the log-transformed band ratio model providing coefficient of determination values, R-2, between 0.83 and 0.88 (0 m-10 m) for the five images considered in the study. The closest fit was found in the depth range 2 m-6 m. Atmospheric correction, bottom type influence, and water column conditions proved to be key factors in the bathymetric derivation using these satellite datasets.

关键词： Bathymetry empirical algorithm atmospheric correction coastal applications

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Triazine Macrocycle Libraries: Synthesis, logD Prediction, and a Surprisingly Hydrophobic, Membrane-Permeable Diamine

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ACS MEDICINAL CHEMISTRY LETTERS 2025年第6期16卷 1017-1023页

作者： Stokes, Gretel A. Patterson-Gardner, Casey J. Engstrom, Alexander M. Menke, Alexander J. Reddy, K. Harsha Vardhan Lokey, R. Scott Simanek, Eric E. Texas Christian Univ Dept Chem & Biochem Ft Worth TX 76109 USA Univ Calif Santa Cruz Dept Chem Santa Cruz CA 95064 USA

A library of triazine macrocycles was obtained to evaluate strategies for predicting lipophilicity using additive algorithms. Two synthetic routes were examined. While both were successful, one proved amenable to solution-phase library synthesis. The octanol-water partition coefficients (logP) were measured using reverse-phase HPLC at pH 10. When experimental and computed values (AlogP) are compared, a linear correlation is observed. That is, while additive algorithms underestimate hydrophobicity by a factor of 100, a simple correction yields accurate predictions. Two macrocycles showed anomalous hydrophobicities at high pH that were borne out in membrane transit (PAMPA) studies. Homodimers containing two primary amines were more hydrophobic than the corresponding heterodimers containing a single amine and a hydrophobic group. Structural analysis and computation provide a rationale for this behavior: the amines engage in an intramolecular hydrogen bond.

关键词： triazine library computation hydrophobicity empirical algorithm PAMPA intramolecularhydrogen bond

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Remote Sensing Estimates of Particulate Organic Carbon Sources in the Zhanjiang Bay Using Sentinel-2 Data and Carbon Isotopes

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REMOTE SENSING 2023年第15期15卷

作者： Yu, Guo Zhong, Yafeng Liu, Sihai Lao, Qibin Chen, Chunqing Fu, Dongyang Chen, Fajin Guangdong Ocean Univ Coll Ocean & Meteorol Zhanjiang 524088 Peoples R China Guangdong Ocean Univ Coll Elect & Informat Engn Zhanjiang 524088 Peoples R China Guangdong Ocean Univ Coll Chem & Environm Sci Zhanjiang 524088 Peoples R China Guangdong Ocean Univ Key Lab Climate Resources & Environm Continental S Zhanjiang 524088 Peoples R China

The source information of coastal particulate organic carbon (POC) with high spatial and temporal resolution is of great significance for the study of marine carbon cycles and marine biogeochemical processes. Over the past decade, satellite ocean color remote sensing has greatly improved our understanding of the spatiotemporal dynamics of ocean particulate organic carbon concentrations. However, due to the complexity of coastal POC sources, remote sensing methods for coastal POC sources have not yet been established. With an attempt to fill the gap, this study developed an algorithm for retrieving coastal POC sources using remote sensing and geochemical isotope technology. The isotope end-member mixing model was used to calculate the proportion of POC sources, and the response relationship between POC source information and in situ remote sensing reflectance (R-rs) was established to develop a retrieval algorithm for POC sources with the following four bands: (R-rs(443)/R-rs(492)) x (R-rs(704)/R-rs(665)). The results showed that the four-band algorithm performed well with R-2, mean absolute percentage error (MAPE) and root mean square error (RMSE) values of 0.78, 33.57% and 13.74%, respectively. Validation against in situ data showed that the four-band algorithm derived calculated the proportion of marine POC accurately, with an MAPE and RMSE of 27.49% and 13.58%, respectively. The accuracy of the algorithm was verified based on the Sentinel-2 data, with an MAPE and RMSE of 28.02% and 15.72%, respectively. Additionally, we found that the proportion of marine POC sources was higher outside the Zhanjiang Bay than inside it using in situ survey data, which was consistent with the retrieved results. Influencing factors of POC sources may be due to the occurrence of phytoplankton blooms outside the bay and the impact of terrestrial inputs inside the bay. Remote sensing in combination with carbon isotopes provides important technical assistance in comprehending the biogeo

关键词： remote sensing geochemical isotope POC sources empirical algorithm Zhanjiang Bay

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