Pub Date : 2023-07-04DOI: 10.1080/01490419.2023.2229019
Alexa Putnam, S. Desai, R. S. Nerem
Abstract An alternative approach to empirical, non-parametric sea state bias (SSB) modeling for satellite altimeter measurements was developed with the intention of providing a simple, transparent, and efficient means to derive both a raw and smoothed SSB solution. This alternative approach, referred to as the interpolation method, maintains the flexibility to generate 2-D or 3-D models using either direct or difference measurements of the sea level anomaly uncorrected for SSB (uSLA). The final, smoothed SSB solution derived using the interpolation method is obtained over three steps, with a supplemental fourth step that consists of estimating a model-dependent dual-frequency ionosphere calibration bias to correct for a relative range + SSB error. A tandem phase analysis for all Topex/Poseidon, Jason 1-3 and Sentinel-6 Michael Freilich satellite altimeter inter-calibration periods reveals that the ionosphere calibration bias removes an ionosphere-related component from intermission bias calculations required to generate the long-term sea level record.
{"title":"Estimation of the Sea State Bias Using the Interpolation Method and Applications to Inter-Mission Calibration","authors":"Alexa Putnam, S. Desai, R. S. Nerem","doi":"10.1080/01490419.2023.2229019","DOIUrl":"https://doi.org/10.1080/01490419.2023.2229019","url":null,"abstract":"Abstract An alternative approach to empirical, non-parametric sea state bias (SSB) modeling for satellite altimeter measurements was developed with the intention of providing a simple, transparent, and efficient means to derive both a raw and smoothed SSB solution. This alternative approach, referred to as the interpolation method, maintains the flexibility to generate 2-D or 3-D models using either direct or difference measurements of the sea level anomaly uncorrected for SSB (uSLA). The final, smoothed SSB solution derived using the interpolation method is obtained over three steps, with a supplemental fourth step that consists of estimating a model-dependent dual-frequency ionosphere calibration bias to correct for a relative range + SSB error. A tandem phase analysis for all Topex/Poseidon, Jason 1-3 and Sentinel-6 Michael Freilich satellite altimeter inter-calibration periods reveals that the ionosphere calibration bias removes an ionosphere-related component from intermission bias calculations required to generate the long-term sea level record.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43076871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-19DOI: 10.1080/01490419.2023.2224513
Alexa Putnam, S. Desai, R. S. Nerem
Abstract Using an empirical, non-parametric sea state bias (SSB) modeling method, which was developed as a tool for SSB error analysis (Putnam, Alexa Forthcoming), we provide an error budget for overall SSB error, as well as the contributing sources of this error budget. The error analysis compares methods used to derive SSB models from observed altimeter measurements, collinear differences of measurements from adjacent repeat cycles, and methods using both collinear and crossover differences of measurements. Our error analysis reveals systematic error caused by ionosphere correction uncertainty in SSB models obtained from direct measurements, and wet troposphere correction uncertainty in SSB models generated using difference measurements. Results also expose a correlation to altimeter measurement error, with the backscatter coefficient accounting for over 20% of the SSB evaluation error and SWH accounting for approximately 50-60%. The error analysis presented here suggests SSB errors are lower than the often-used approximation of SSB error as 1% of SWH, except at SWH values less than 2 m where errors are likely larger. We find that increasing the pulse repetition frequency of the altimeter reduces SSB errors. The future for improving empirical, nonparametric SSB estimation primarily depends on improving measured SWH.
{"title":"Estimation of the sea state bias error budget for pulse-limited satellite altimetry","authors":"Alexa Putnam, S. Desai, R. S. Nerem","doi":"10.1080/01490419.2023.2224513","DOIUrl":"https://doi.org/10.1080/01490419.2023.2224513","url":null,"abstract":"Abstract Using an empirical, non-parametric sea state bias (SSB) modeling method, which was developed as a tool for SSB error analysis (Putnam, Alexa Forthcoming), we provide an error budget for overall SSB error, as well as the contributing sources of this error budget. The error analysis compares methods used to derive SSB models from observed altimeter measurements, collinear differences of measurements from adjacent repeat cycles, and methods using both collinear and crossover differences of measurements. Our error analysis reveals systematic error caused by ionosphere correction uncertainty in SSB models obtained from direct measurements, and wet troposphere correction uncertainty in SSB models generated using difference measurements. Results also expose a correlation to altimeter measurement error, with the backscatter coefficient accounting for over 20% of the SSB evaluation error and SWH accounting for approximately 50-60%. The error analysis presented here suggests SSB errors are lower than the often-used approximation of SSB error as 1% of SWH, except at SWH values less than 2 m where errors are likely larger. We find that increasing the pulse repetition frequency of the altimeter reduces SSB errors. The future for improving empirical, nonparametric SSB estimation primarily depends on improving measured SWH.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48816605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-19DOI: 10.1080/01490419.2023.2223764
Minzhi Xiang, Hongzhou Chai, Xiao Yin, Zhenqiang Du, Kaidi Jin
Abstract High-precision position, velocity and attitude information is the premise for the unmanned surface vehicle (USV) to perform various tasks. The traditional navigation technology of USV is to combine RTK (real-time kinematics) with MEMS (micro-electromechanical system). In order to avoid bi-directional communication of RTK/MEMS, a loosely coupled PPP (precise point positioning)-RTK/MEMS navigation method is proposed in this contribution, where the un-combined PPP-RTK positioning model and advanced time-differenced carrier-phase (TDCP) velocity determination model is adopted. When the reference stations are far away from the user, i.e., more than 55 km, the centimetre-level positioning results can be achieved and especially 99% horizontal error is less than 10 cm. Compared with the TDCP-only centimetre-per-second-level velocity accuracy, the proposed method can increase to accuracy of the order of millimetres per second. In terms of attitude determination accuracy, the roll and pitch are better than 0.1° and yaw is better than 0.5°, showing a similar performance to the nominal accuracy. Therefore, the proposed PPP-RTK/MEMS integration method can be a promising USV navigation solution in the offshore area.
{"title":"Precise Navigation of USV Based on PPP-RTK/MEMS in the Offshore Environment","authors":"Minzhi Xiang, Hongzhou Chai, Xiao Yin, Zhenqiang Du, Kaidi Jin","doi":"10.1080/01490419.2023.2223764","DOIUrl":"https://doi.org/10.1080/01490419.2023.2223764","url":null,"abstract":"Abstract High-precision position, velocity and attitude information is the premise for the unmanned surface vehicle (USV) to perform various tasks. The traditional navigation technology of USV is to combine RTK (real-time kinematics) with MEMS (micro-electromechanical system). In order to avoid bi-directional communication of RTK/MEMS, a loosely coupled PPP (precise point positioning)-RTK/MEMS navigation method is proposed in this contribution, where the un-combined PPP-RTK positioning model and advanced time-differenced carrier-phase (TDCP) velocity determination model is adopted. When the reference stations are far away from the user, i.e., more than 55 km, the centimetre-level positioning results can be achieved and especially 99% horizontal error is less than 10 cm. Compared with the TDCP-only centimetre-per-second-level velocity accuracy, the proposed method can increase to accuracy of the order of millimetres per second. In terms of attitude determination accuracy, the roll and pitch are better than 0.1° and yaw is better than 0.5°, showing a similar performance to the nominal accuracy. Therefore, the proposed PPP-RTK/MEMS integration method can be a promising USV navigation solution in the offshore area.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46772472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-29DOI: 10.1080/01490419.2023.2208289
Emily J. Tidey, R. Odolinski
Abstract The use of Real Time Kinematic (RTK) Global Navigation Satellite System (GNSS) for accurate horizontal and vertical measurements in the marine environment has been considered since the late-1980’s and tested from the 1990’s when GPS and GLONASS were the only operational constellations available and high-cost multi-frequency receiver equipment was required. This paper modernizes the conversation using multi-constellation, low-cost, single-frequency RTK GNSS measurements and proves their value with accurate positioning and tide measurements. Our tests show average stationary horizontal positioning measurements using this equipment are suitable (95% CI) for the most stringent International Hydrographic Organization (IHO) Standard S-44 ‘Exclusive Order’ at base station ranges of up to 27 km. Vertical observations on a moving platform, smoothed using a baseline distance-dependent moving average filter show the equipment and method are comparable with traditional electronic tide gauge observations over the same base station range. All of our measurement results show the potential to improve total uncertainty calculations undertaken by hydrographers, engineers and scientists in the marine realm, while the low-cost equipment raises the possibility that more measurements can be taken, leading to improvements in monitoring, modelling and understanding the marine environment.
{"title":"Low-cost multi-GNSS, single-frequency RTK averaging for marine applications: accurate stationary positioning and vertical tide measurements","authors":"Emily J. Tidey, R. Odolinski","doi":"10.1080/01490419.2023.2208289","DOIUrl":"https://doi.org/10.1080/01490419.2023.2208289","url":null,"abstract":"Abstract The use of Real Time Kinematic (RTK) Global Navigation Satellite System (GNSS) for accurate horizontal and vertical measurements in the marine environment has been considered since the late-1980’s and tested from the 1990’s when GPS and GLONASS were the only operational constellations available and high-cost multi-frequency receiver equipment was required. This paper modernizes the conversation using multi-constellation, low-cost, single-frequency RTK GNSS measurements and proves their value with accurate positioning and tide measurements. Our tests show average stationary horizontal positioning measurements using this equipment are suitable (95% CI) for the most stringent International Hydrographic Organization (IHO) Standard S-44 ‘Exclusive Order’ at base station ranges of up to 27 km. Vertical observations on a moving platform, smoothed using a baseline distance-dependent moving average filter show the equipment and method are comparable with traditional electronic tide gauge observations over the same base station range. All of our measurement results show the potential to improve total uncertainty calculations undertaken by hydrographers, engineers and scientists in the marine realm, while the low-cost equipment raises the possibility that more measurements can be taken, leading to improvements in monitoring, modelling and understanding the marine environment.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46480395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-27DOI: 10.1080/01490419.2023.2213838
Kaidi Jin, Hongzhou Chai, Chuhan Su, Minzhi Xiang, Mingchen Shi
Abstract Doppler velocity logger (DVL) error parameters can significantly influence the navigation accuracy of DVL/strapdown inertial navigation system (SINS) integration for unmanned underwater vehicles (UUV). To improve the navigation accuracy of UUV, this study proposes a two-stage DVL calibration method aided by global navigation satellite system (GNSS) measurements. First, utilizing the velocity of GNSS/SINS integrated navigation, the scale factor error of DVL is calculated by the moduli of velocities in UUV body frame and DVL instrument frame. Then, using the measurements throughout the calibration process, the calibration problem of the installation angle is converted to a nonlinear constraint optimization problem by describing the angle as a unit quaternion. Moreover, an easy-to-implement quaternion estimation algorithm is chosen to solve the problem and obtain the optimal quaternion. Simulation and sea trial indicate that the proposed method can rapidly and accurately estimate the DVL error parameters in different scenarios, and the position accuracy of the DVL/SINS system is improved.
{"title":"A GNSS-aided DVL calibration method based on quaternion estimation for underwater vehicles","authors":"Kaidi Jin, Hongzhou Chai, Chuhan Su, Minzhi Xiang, Mingchen Shi","doi":"10.1080/01490419.2023.2213838","DOIUrl":"https://doi.org/10.1080/01490419.2023.2213838","url":null,"abstract":"Abstract Doppler velocity logger (DVL) error parameters can significantly influence the navigation accuracy of DVL/strapdown inertial navigation system (SINS) integration for unmanned underwater vehicles (UUV). To improve the navigation accuracy of UUV, this study proposes a two-stage DVL calibration method aided by global navigation satellite system (GNSS) measurements. First, utilizing the velocity of GNSS/SINS integrated navigation, the scale factor error of DVL is calculated by the moduli of velocities in UUV body frame and DVL instrument frame. Then, using the measurements throughout the calibration process, the calibration problem of the installation angle is converted to a nonlinear constraint optimization problem by describing the angle as a unit quaternion. Moreover, an easy-to-implement quaternion estimation algorithm is chosen to solve the problem and obtain the optimal quaternion. Simulation and sea trial indicate that the proposed method can rapidly and accurately estimate the DVL error parameters in different scenarios, and the position accuracy of the DVL/SINS system is improved.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47903907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-23DOI: 10.1080/01490419.2023.2213840
Yanhong Wang, Yilan Chen, Yikai Feng, Zhipeng Dong, Xiaoyu Liu
Abstract Satellite-derived bathymetry is an economic and effective method of obtaining large-scale, high-resolution bathymetric information. At present, bathymetric inversion models require existing bathymetric data as a necessary condition, but these may be difficult to obtain around many small islands. Under the condition of sparse measurement data, many common methods have low levels of accuracy. This paper proposes a method of transferring a bathymetric model for an island that has in situ data to an island that has little in situ data. First, in situ data are used to establish a high-precision satellite bathymetry model for a given island. Second, this model is transplanted to other islands. The addition of just 2–3 data points to correct the model results can reduce the mean relative error to 6.62% in the range of 0–20 m. This is close to the accuracy of establishing the model using a large number of measurement data (mean relative error of 5.25%).
{"title":"Multispectral Satellite-Derived Bathymetry Based on Sparse Prior Measured Data","authors":"Yanhong Wang, Yilan Chen, Yikai Feng, Zhipeng Dong, Xiaoyu Liu","doi":"10.1080/01490419.2023.2213840","DOIUrl":"https://doi.org/10.1080/01490419.2023.2213840","url":null,"abstract":"Abstract Satellite-derived bathymetry is an economic and effective method of obtaining large-scale, high-resolution bathymetric information. At present, bathymetric inversion models require existing bathymetric data as a necessary condition, but these may be difficult to obtain around many small islands. Under the condition of sparse measurement data, many common methods have low levels of accuracy. This paper proposes a method of transferring a bathymetric model for an island that has in situ data to an island that has little in situ data. First, in situ data are used to establish a high-precision satellite bathymetry model for a given island. Second, this model is transplanted to other islands. The addition of just 2–3 data points to correct the model results can reduce the mean relative error to 6.62% in the range of 0–20 m. This is close to the accuracy of establishing the model using a large number of measurement data (mean relative error of 5.25%).","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46702067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In recent years, two types of macroalgae, namely, Ulva prolifera and Sargassum horneri, have appeared occasionally together in the Yellow Sea and the East China Sea. Remote sensing enables timely and cost-effective observation of macroalgae across large areas. In the available studies, the recognition and classification of the two macroalgae are primarily based on spectral difference analysis. In this study, the spectral features, indices and textural feature parameters of the macroalgae targets were extracted and a preliminary multi-feature dataset was constructed based on Sentinel-2 images. Feature selection was performed using SHAP-based importance analysis and Bhattacharyya distance. From this, a multi-feature dataset was created and used as an input to a deep semantic segmentation network of improved ResUnet. The experiments of intelligent recognition and classification of U. prolifera and S. horneri were carried out using the proposed multi-feature-based ResUnet algorithm, with specific F1-scores of 96.7% and 96.8%, respectively. The proposed multi-feature-based ResUnet algorithm can obtain efficient and high-accuracy results for the recognition and classification of marine floating macroalgae. It achieves accurate remote sensing monitoring of the two types of marine floating macroalgae and has significant theoretical research significance and practical application value.
{"title":"Distinguishing Ulva prolifera and Sargassum horneri by using multi-feature-based ResUnet algorithm","authors":"Jinyu Li, Shengjia Zhang, Chao Zhang, Hong-chun Zhu","doi":"10.1080/01490419.2023.2197265","DOIUrl":"https://doi.org/10.1080/01490419.2023.2197265","url":null,"abstract":"Abstract In recent years, two types of macroalgae, namely, Ulva prolifera and Sargassum horneri, have appeared occasionally together in the Yellow Sea and the East China Sea. Remote sensing enables timely and cost-effective observation of macroalgae across large areas. In the available studies, the recognition and classification of the two macroalgae are primarily based on spectral difference analysis. In this study, the spectral features, indices and textural feature parameters of the macroalgae targets were extracted and a preliminary multi-feature dataset was constructed based on Sentinel-2 images. Feature selection was performed using SHAP-based importance analysis and Bhattacharyya distance. From this, a multi-feature dataset was created and used as an input to a deep semantic segmentation network of improved ResUnet. The experiments of intelligent recognition and classification of U. prolifera and S. horneri were carried out using the proposed multi-feature-based ResUnet algorithm, with specific F1-scores of 96.7% and 96.8%, respectively. The proposed multi-feature-based ResUnet algorithm can obtain efficient and high-accuracy results for the recognition and classification of marine floating macroalgae. It achieves accurate remote sensing monitoring of the two types of marine floating macroalgae and has significant theoretical research significance and practical application value.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43063267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-27DOI: 10.1080/01490419.2023.2200043
V. Noujas, R. S. Kankara, B. Rajan
Abstract Episodic extreme waves caused by cyclones can have catastrophic consequences for coastal zones, including drastic beach morphology changes. The present study analyzed the beach morphological changes from Kakinada to Konapapapeta on the southeast coast of India before, during, and after the tropical cyclone Phethai using field survey and numerical modeling. Beach profiles were collected using Trimble RTK GPS and shoreline tracking was performed with handheld GPS. Numerical modeling was carried out using MIKE software to estimate the sediment transport rate before, during, and after the cyclone. Although the intensity of the cyclone reduced to a deep depression before landfall, several morphological changes were observed. Erosion was higher in the northern sector, where the beach width was less, and prominent scarps were seen throughout this region after the cyclone. The inundation varied from 40 to 120 m during the cyclone due to a storm surge of 0.5 to 1 m. During the cyclone, significant wave heights reached up to 4 m. The gross sediment transport rate is 3 to 13 times greater during the cyclone period than during the non-cyclone period. The maximum gross sediment transport rate during the Phethai cyclone was 1040 m3/day. Sediment transport was estimated for the same site for the non-cyclone year 2019, and the gross transport rate was 26,174 m3. As it is projected that extreme events are likely to increase due to climate change, output from this type of study is vital to environmental managers to assess erosion and develop long-term mitigation plans.
{"title":"Assessment of beach morphological changes in the east coast of India during cyclone Phethai, through field data and numerical modeling","authors":"V. Noujas, R. S. Kankara, B. Rajan","doi":"10.1080/01490419.2023.2200043","DOIUrl":"https://doi.org/10.1080/01490419.2023.2200043","url":null,"abstract":"Abstract Episodic extreme waves caused by cyclones can have catastrophic consequences for coastal zones, including drastic beach morphology changes. The present study analyzed the beach morphological changes from Kakinada to Konapapapeta on the southeast coast of India before, during, and after the tropical cyclone Phethai using field survey and numerical modeling. Beach profiles were collected using Trimble RTK GPS and shoreline tracking was performed with handheld GPS. Numerical modeling was carried out using MIKE software to estimate the sediment transport rate before, during, and after the cyclone. Although the intensity of the cyclone reduced to a deep depression before landfall, several morphological changes were observed. Erosion was higher in the northern sector, where the beach width was less, and prominent scarps were seen throughout this region after the cyclone. The inundation varied from 40 to 120 m during the cyclone due to a storm surge of 0.5 to 1 m. During the cyclone, significant wave heights reached up to 4 m. The gross sediment transport rate is 3 to 13 times greater during the cyclone period than during the non-cyclone period. The maximum gross sediment transport rate during the Phethai cyclone was 1040 m3/day. Sediment transport was estimated for the same site for the non-cyclone year 2019, and the gross transport rate was 26,174 m3. As it is projected that extreme events are likely to increase due to climate change, output from this type of study is vital to environmental managers to assess erosion and develop long-term mitigation plans.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48281847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-10DOI: 10.1080/01490419.2023.2200212
Sheikh Mohammed Rabiul Alam, M. S. Hossain
Abstract As is well-documented, cloud cover (CC) obscures the target object and water depth and turbidity impede optical remote sensing (RS). Therefore, Landsat imagery acquired under cloud-free (CFI) and low-tide (LTI) conditions are considered ‘quality’ observations when mapping tidal wetlands such as saltmarsh. Although it is essential to estimate probabilities of acquiring at least one CFI and LTI, previous studies rarely addressed in RS of saltmarsh land cover (SLC). In order to evaluate the probabilities of acquiring at least one CFI and LTI in a year, a month, a season, a pair of seasons, or a certain time interval within a year over south-eastern Bangladesh, all images acquired between 1988 and 2019 were examined. The results indicate that SLC applications are generally affected by CC and tide heights; an average yearly CF probability of 16% can be acquired under LT conditions. Seasonal variations in CFI are apparent and there is a significant shortage of clear observation during the monsoon. The higher number of CFI may not guarantee a higher probability of LTI due to tide dynamics. The availability of both CFI and LTI can be remarkably improved if the present 16-day interval time of Landsat’s acquisition is increased.
{"title":"Probabilities of acquiring cloud-free and low-tide Landsat observations for mapping saltmarsh over south-eastern Bangladesh from 1980 to 2019","authors":"Sheikh Mohammed Rabiul Alam, M. S. Hossain","doi":"10.1080/01490419.2023.2200212","DOIUrl":"https://doi.org/10.1080/01490419.2023.2200212","url":null,"abstract":"Abstract As is well-documented, cloud cover (CC) obscures the target object and water depth and turbidity impede optical remote sensing (RS). Therefore, Landsat imagery acquired under cloud-free (CFI) and low-tide (LTI) conditions are considered ‘quality’ observations when mapping tidal wetlands such as saltmarsh. Although it is essential to estimate probabilities of acquiring at least one CFI and LTI, previous studies rarely addressed in RS of saltmarsh land cover (SLC). In order to evaluate the probabilities of acquiring at least one CFI and LTI in a year, a month, a season, a pair of seasons, or a certain time interval within a year over south-eastern Bangladesh, all images acquired between 1988 and 2019 were examined. The results indicate that SLC applications are generally affected by CC and tide heights; an average yearly CF probability of 16% can be acquired under LT conditions. Seasonal variations in CFI are apparent and there is a significant shortage of clear observation during the monsoon. The higher number of CFI may not guarantee a higher probability of LTI due to tide dynamics. The availability of both CFI and LTI can be remarkably improved if the present 16-day interval time of Landsat’s acquisition is increased.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43915105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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