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Bioinspired Polarized Optical Flow Enables Turbid Underwater Target Motion Estimation
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作者 CHENG Haoyuan ZHAO Shujie +2 位作者 ZHU Jinchi YU Hao CHU Jinkui 《Journal of Ocean University of China》 SCIE CAS CSCD 2024年第4期915-923,共9页
Underwater target motion estimation is a challenge for ocean military and scientific research.In this work,we propose a method based on the combination of polarization imaging and optical flow for turbid underwater ta... Underwater target motion estimation is a challenge for ocean military and scientific research.In this work,we propose a method based on the combination of polarization imaging and optical flow for turbid underwater target detection.Polarization imaging can reduce the influence of backscattered light and obtain high-quality images underwater.The optical flow shows the motion and structural information of the target.We use polarized optical flow to obtain the optical flow field and estimate the target motion.The experimental results of different targets under varying water turbidity levels illustrate that our method is realizable and robust.The precision is verified by comparing the results with the precise displacement data and calculating two error measures.The proposed method based on polarized optical flow can obtain accurate displacement information and a good recognition effect.Moving target segmentation based on the Otsu method further proves the superiority of the polarized optical flow under turbid water.This study is valuable for target detection and motion estimation in scattering environments. 展开更多
关键词 turbid underwater motion estimation polarization imaging optical flow
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Phase-Based Optical Flow Method with Optimized Parameter Settings for Enhancing Displacement Measurement Adaptability
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作者 Zhaoxin Peng Menglian Liu +2 位作者 Zhiliang Wang Wei Liu Xian Wang 《Open Journal of Applied Sciences》 2024年第5期1165-1184,共20页
To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizi... To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring. 展开更多
关键词 Displacement Measurement Phase-Based optical Flow Optimized Parameter Setting
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Three-dimensional color particle image velocimetry based on a cross-correlation and optical flow method
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作者 单良 熊俊哲 +4 位作者 施飞杨 洪波 简娟 詹虹晖 孔明 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第5期88-96,共9页
Rainbow particle image velocimetry(PIV)can restore the three-dimensional velocity field of particles with a single camera;however,it requires a relatively long time to complete the reconstruction.This paper proposes a... Rainbow particle image velocimetry(PIV)can restore the three-dimensional velocity field of particles with a single camera;however,it requires a relatively long time to complete the reconstruction.This paper proposes a hybrid algorithm that combines the fast Fourier transform(FFT)based co-correlation algorithm and the Horn–Schunck(HS)optical flow pyramid iterative algorithm to increase the reconstruction speed.The Rankine vortex simulation experiment was performed,in which the particle velocity field was reconstructed using the proposed algorithm and the rainbow PIV method.The average endpoint error and average angular error of the proposed algorithm were roughly the same as those of the rainbow PIV algorithm;nevertheless,the reconstruction time was 20%shorter.Furthermore,the effect of velocity magnitude and particle density on the reconstruction results was analyzed.In the end,the performance of the proposed algorithm was verified using real experimental single-vortex and double-vortex datasets,from which a similar particle velocity field was obtained compared with the rainbow PIV algorithm.The results show that the reconstruction speed of the proposed hybrid algorithm is approximately 25%faster than that of the rainbow PIV algorithm. 展开更多
关键词 particle image velocimetry color light cross-correlation and optical flow method VORTEX
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FeatureMatching Combining Variable Velocity Model with Reverse Optical Flow
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作者 Chang Zhao Wei Sun +3 位作者 Xiaorui Zhang Xiaozheng He Jun Zuo Wei Zhao 《Computer Systems Science & Engineering》 SCIE EI 2023年第5期1083-1094,共12页
The ORB-SLAM2 based on the constant velocity model is difficult to determine the search window of the reprojection of map points when the objects are in variable velocity motion,which leads to a false matching,with an... The ORB-SLAM2 based on the constant velocity model is difficult to determine the search window of the reprojection of map points when the objects are in variable velocity motion,which leads to a false matching,with an inaccurate pose estimation or failed tracking.To address the challenge above,a new method of feature point matching is proposed in this paper,which combines the variable velocity model with the reverse optical flow method.First,the constant velocity model is extended to a new variable velocity model,and the expanded variable velocity model is used to provide the initial pixel shifting for the reverse optical flow method.Then the search range of feature points is accurately determined according to the results of the reverse optical flow method,thereby improving the accuracy and reliability of feature matching,with strengthened interframe tracking effects.Finally,we tested on TUM data set based on the RGB-D camera.Experimental results show that this method can reduce the probability of tracking failure and improve localization accuracy on SLAM(Simultaneous Localization and Mapping)systems.Compared with the traditional ORB-SLAM2,the test error of this method on each sequence in the TUM data set is significantly reduced,and the root mean square error is only 63.8%of the original system under the optimal condition. 展开更多
关键词 Visual SLAM feature point matching variable velocity model reverse optical flow
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Abnormal Crowd Behavior Detection Based on the Entropy of Optical Flow 被引量:1
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作者 Zheyi Fan Wei Li +1 位作者 Zhonghang He Zhiwen Liu 《Journal of Beijing Institute of Technology》 EI CAS 2019年第4期756-763,共8页
To improve the detection accuracy and robustness of crowd anomaly detection,especially crowd emergency evacuation detection,the abnormal crowd behavior detection method is proposed.This method is based on the improved... To improve the detection accuracy and robustness of crowd anomaly detection,especially crowd emergency evacuation detection,the abnormal crowd behavior detection method is proposed.This method is based on the improved statistical global optical flow entropy which can better describe the degree of chaos of crowd.First,the optical flow field is extracted from the video sequences and a 2D optical flow histogram is gained.Then,the improved optical flow entropy,combining information theory with statistical physics is calculated from 2D optical flow histograms.Finally,the anomaly can be detected according to the abnormality judgment formula.The experimental results show that the detection accuracy achieved over 95%in three public video datasets,which indicates that the proposed algorithm outperforms other state-of-the-art algorithms. 展开更多
关键词 abnormal events detection optical flows entropy crowded scenes crowd behavior
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Obstacle Avoidance of Flapping⁃Wing Air Vehicles Based on Optical Flow and Fuzzy Control 被引量:12
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作者 FU Qiang WANG Jin +2 位作者 GONG Le WANG Jingyuan HE Wei 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第2期206-215,共10页
The flapping-wing air vehicle(FWAV)is a kind of bio-inspired robot whose wings can flap up and down like bird and insect wings.A vision-based obstacle avoidance method for FWAVs is proposed in this paper.First,the Far... The flapping-wing air vehicle(FWAV)is a kind of bio-inspired robot whose wings can flap up and down like bird and insect wings.A vision-based obstacle avoidance method for FWAVs is proposed in this paper.First,the Farneback algorithm is used to calculate the optical flow field of the first-view video frames taken by the on-board image transmission camera.Based on the optical flow information,a fuzzy obstacle avoidance controller is then designed to generate the FWAV steering commands.Experimental results show that the proposed obstacle avoidance method can accurately identify obstacles and achieve obstacle avoidance for FWAVs. 展开更多
关键词 dense optical flow monocular vision obstacle avoidance flapping-wing air vehicle fuzzy control
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6-DOF motion estimation using optical flow based on dual cameras 被引量:3
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作者 刘梦瑶 王岩 郭雷 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第2期459-466,共8页
Because of its characteristics of simple algorithm and hardware, optical flow-based motion estimation has become a hot research field, especially in GPS-denied environment. Optical flow could be used to obtain the air... Because of its characteristics of simple algorithm and hardware, optical flow-based motion estimation has become a hot research field, especially in GPS-denied environment. Optical flow could be used to obtain the aircraft motion information, but the six-(degree of freedom)(6-DOF) motion still couldn't be accurately estimated by existing methods. The purpose of this work is to provide a motion estimation method based on optical flow from forward and down looking cameras, which doesn't rely on the assumption of level flight. First, the distribution and decoupling method of optical flow from forward camera are utilized to get attitude. Then, the resulted angular velocities are utilized to obtain the translational optical flow of the down camera, which can eliminate the influence of rotational motion on velocity estimation. Besides, the translational motion estimation equation is simplified by establishing the relation between the depths of feature points and the aircraft altitude. Finally, simulation results show that the method presented is accurate and robust. 展开更多
关键词 optical flow motion estimation dual cameras six degree-of-freedom(6-DOF)
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Contributions to Hom-Schunck optical flow equations-part I: Stability and rate of convergence of classical algorithm 被引量:2
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作者 DONG Guo-hua AN Xiang-jing FANG Yu-qiang HU De-wen 《Journal of Central South University》 SCIE EI CAS 2013年第7期1909-1918,共10页
Globally exponential stability (which implies convergence and uniqueness) of their classical iterative algorithm is established using methods of heat equations and energy integral after embedding the discrete iterat... Globally exponential stability (which implies convergence and uniqueness) of their classical iterative algorithm is established using methods of heat equations and energy integral after embedding the discrete iteration into a continuous flow. The stability condition depends explicitly on smoothness of the image sequence, size of image domain, value of the regularization parameter, and finally discretization step. Specifically, as the discretization step approaches to zero, stability holds unconditionally. The analysis also clarifies relations among the iterative algorithm, the original variation formulation and the PDE system. The proper regularity of solution and natural images is briefly surveyed and discussed. Experimental results validate the theoretical claims both on convergence and exponential stability. 展开更多
关键词 optical flow Hom-Schunck equations globally exponential stability convergence convergence rate heat equations energy integral and estimate Gronwall inequality natural images REGULARITY
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Discontinuity-preserving optical flow algorithm 被引量:2
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作者 Yuan Lei Li Jinzong Li Dongdong 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2007年第2期347-354,共8页
A modification of Horn and Schunk's approach is investigated, which leads to a better preservation of flow discontinuities. It improves Horn-Schunk model in three aspects: (1) It replaces the smooth weight coeffic... A modification of Horn and Schunk's approach is investigated, which leads to a better preservation of flow discontinuities. It improves Horn-Schunk model in three aspects: (1) It replaces the smooth weight coefficient in the energy equation by the variable weight coefficient. (2) It adopts a novel method to compute the mean velocity. The novel method also reflects the effect of the intensity difference on the image velocity diffusion. (3) It introduces a more efficient iterative method than the Gauss-Seidel method to solve the associated Euler-Lagrange equation. The experiment results validate the better effect of the improved method on preserving discontinuities. 展开更多
关键词 optical flow Image sequences Differential methods PNSR.
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A Closed Form Solution to Segment 3D Motion Using Straight-line Optical Flow 被引量:2
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作者 张婧 石繁槐 +1 位作者 马文娟 刘允才 《Journal of Shanghai Jiaotong university(Science)》 EI 2008年第1期76-80,共5页
A closed form solution to the problem of segmenting multiple 3D motion models was proposed from straight-line optical flow. It introduced the multibody line optical flow constraint (MLOFC), a polynomial equation relat... A closed form solution to the problem of segmenting multiple 3D motion models was proposed from straight-line optical flow. It introduced the multibody line optical flow constraint (MLOFC), a polynomial equation relating motion models and line parameters. The motion models can be obtained analytically as the derivative of the MLOFC at the corresponding line measurement, without knowing the motion model associated with that line. Experiments on real and synthetic sequences were also presented. 展开更多
关键词 SEGMENTATION optical flow LINE generalized principal component analysis (GPCA)
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A ROBUST OPTICAL FLOW COMPUTATION 被引量:2
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作者 Lu Zongqing XieWeixin Pei Jihong 《Journal of Electronics(China)》 2007年第5期635-641,共7页
This paper presents a new method for robust and accurate optical flow estimation.The sig- nificance of this work is twofold.Firstly,the idea of bi-directional scheme is adopted to reduce the model error of optical flo... This paper presents a new method for robust and accurate optical flow estimation.The sig- nificance of this work is twofold.Firstly,the idea of bi-directional scheme is adopted to reduce the model error of optical flow equation,which allows the second order Taylor's expansion of optical flow equation for accurate solution without much extra computational burden;Secondly,this paper establishs a new optical flow equation based on LSCM (Local Structure Constancy Model) instead of BCM (Brightness Constancy Model),namely the optical flow equation does not act on scalar but on tensor-valued (ma- trix-valued) field,due to the two reason:(1) structure tensor-value contains local spatial structure information,which provides us more useable cues for computation than scalar;(2) local image structure is less sensitive to illumination variation than intensity,which weakens the disturbance of non-uniform illumination in real sequences.Qualitative and quantitative results for synthetic and real-world scenes show that the new method can produce an accurate and robust results. 展开更多
关键词 optical flow TENSOR Brightness Constancy Model (BCM) Local Structure Constancy Model (LSCM)
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Measuring In-Plane Micro-Motion of Micro-Structure Using Optical Flow 被引量:1
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作者 金翠云 靳世久 +1 位作者 栗大超 王建林 《Transactions of Tianjin University》 EI CAS 2009年第1期19-22,共4页
Optical flow method is one of the most important methods of analyzing motion images. Optical flow field is used to analyze characteristics of motion objects. According to motion features of micro-electronic mechani-ca... Optical flow method is one of the most important methods of analyzing motion images. Optical flow field is used to analyze characteristics of motion objects. According to motion features of micro-electronic mechani-cal system (MEMS) micro-structure, the optical algorithm based on label field and neighborhood optimization is presented to analyze the in-plane micro-motion of micro-structure. Firstly, high speed motion states for each fre-quency segment of micro-structure in cyclic motion are frozen based on stroboscopic principle. Thus a series of dynamic images of micro-structure are obtained. Secondly, the presented optical algorithm is used to analyze the image sequences, and can obtain reliable and precise optical field and reduce computing time. As micro-resonator of testing object, the phase-amplitude curve of micro-structure is derived. Experimental results indicate that the meas-urement precision of the presented algorithm is high, and measurement repeatability reaches 40 nm under the same experiment condition. 展开更多
关键词 micro-electronic mechanical system (MEMS) MICRO-MOTION stroboscopic imaging optical flow label field
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Optical Flow with Learning Feature for Deformable Medical Image Registration 被引量:1
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作者 Jinrong Hu Lujin Li +3 位作者 Ying Fu Maoyang Zou Jiliu Zhou Shanhui Sun 《Computers, Materials & Continua》 SCIE EI 2022年第5期2773-2788,共16页
Deformable medical image registration plays a vital role in medical image applications,such as placing different temporal images at the same time point or different modality images into the same coordinate system.Vari... Deformable medical image registration plays a vital role in medical image applications,such as placing different temporal images at the same time point or different modality images into the same coordinate system.Various strategies have been developed to satisfy the increasing needs of deformable medical image registration.One popular registration method is estimating the displacement field by computing the optical flow between two images.The motion field(flow field)is computed based on either gray-value or handcrafted descriptors such as the scale-invariant feature transform(SIFT).These methods assume that illumination is constant between images.However,medical images may not always satisfy this assumption.In this study,we propose a metric learning-based motion estimation method called Siamese Flow for deformable medical image registration.We train metric learners using a Siamese network,which produces an image patch descriptor that guarantees a smaller feature distance in two similar anatomical structures and a larger feature distance in two dissimilar anatomical structures.In the proposed registration framework,the flow field is computed based on such features and is close to the real deformation field due to the excellent feature representation ability of the Siamese network.Experimental results demonstrate that the proposed method outperforms the Demons,SIFT Flow,Elastix,and VoxelMorph networks regarding registration accuracy and robustness,particularly with large deformations. 展开更多
关键词 Deformation registration feature extraction optical flow convolutional neural network
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Study on Local Optical Flow Method Based on YOLOv3 in Human Behavior Recognition 被引量:2
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作者 Hao Zheng Jianfang Liu Mengyi Liao 《Journal of Computer and Communications》 2021年第1期10-18,共9页
In the process of human behavior recognition, the traditional dense optical flow method has too many pixels and too much overhead, which limits the running speed. This paper proposed a method combing YOLOv3 (You Only ... In the process of human behavior recognition, the traditional dense optical flow method has too many pixels and too much overhead, which limits the running speed. This paper proposed a method combing YOLOv3 (You Only Look Once v3) and local optical flow method. Based on the dense optical flow method, the optical flow modulus of the area where the human target is detected is calculated to reduce the amount of computation and save the cost in terms of time. And then, a threshold value is set to complete the human behavior identification. Through design algorithm, experimental verification and other steps, the walking, running and falling state of human body in real life indoor sports video was identified. Experimental results show that this algorithm is more advantageous for jogging behavior recognition. 展开更多
关键词 YOLOv3 Local optical Flow Method Human Behavior Recognition
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Single-Phase Velocity Determination Based in Video and Sub-Images Processing:An Optical Flow Method Implemented with Support of a Programmed MatLab Structured Script 被引量:1
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作者 Andreas Nascimento Edson Da Costa Bortoni +2 位作者 José Luiz Goncalves Pedro Antunes Duarte Mauro Hugo Mathias 《Journal of Software Engineering and Applications》 2015年第6期290-294,共5页
Important in many different sectors of the industry, the determination of stream velocity has become more and more important due to measurements precision necessity, in order to determine the right production rates, d... Important in many different sectors of the industry, the determination of stream velocity has become more and more important due to measurements precision necessity, in order to determine the right production rates, determine the volumetric production of undesired fluid, establish automated controls based on these measurements avoiding over-flooding or over-production, guaranteeing accurate predictive maintenance, etc. Difficulties being faced have been the determination of the velocity of specific fluids embedded in some others, for example, determining the gas bubbles stream velocity flowing throughout liquid fluid phase. Although different and already applicable methods have been researched and already implemented within the industry, a non-intrusive automated way of providing those stream velocities has its importance, and may have a huge impact in projects budget. Knowing the importance of its determination, this developed script uses a methodology of breaking-down real-time videos media into frame images, analyzing by pixel correlations possible superposition matches for further gas bubbles stream velocity estimation. In raw sense, the script bases itself in functions and procedures already available in MatLab, which can be used for image processing and treatments, allowing the methodology to be implemented. Its accuracy after the running test was of around 97% (ninety-seven percent);the raw source code with comments had almost 3000 (three thousand) characters;and the hardware placed for running the code was an Intel Core Duo 2.13 [Ghz] and 2 [Gb] RAM memory capable workstation. Even showing good results, it could be stated that just the end point correlations were actually getting to the final solution. So that, making use of self-learning functions or neural network, one could surely enhance the capability of the application to be run in real-time without getting exhaust by iterative loops. 展开更多
关键词 optical Flow Single-Phase Velocity Video and Image Processing Sensing MatLab Script
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A novel algorithm for ocean wave direction inversion from X-band radar images based on optical flow method
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作者 WANG Li CHENG Yunfei +1 位作者 HONG Lijuan LIU Xinyu 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第3期88-93,共6页
As one of the important sea state parameters for navigation safety and coastal resource management, the ocean wave direction represents the propagation direction of the wave. A novel algorithm based on an optical flow... As one of the important sea state parameters for navigation safety and coastal resource management, the ocean wave direction represents the propagation direction of the wave. A novel algorithm based on an optical flow method is developed for the ocean wave direction inversion of the ocean wave fields imaged by the X-band radar continuously. The proposed algorithm utilizes the echo images received by the X-band wave monitoring radar to estimate the optical flow motion, and then the actual wave propagation direction can be obtained by taking a weighted average of the motion vector for each pixel. Compared with the traditional ocean wave direction inversion method based on frequency-domain, the novel algorithm is fully using a time-domain signal processing method without determination of a current velocity and a modulation transfer function(MTF). In the meantime,the novel algorithm is simple, efficient and there is no need to do something more complicated here. Compared with traditional ocean wave direction inversion method, the ocean wave direction of derived by using this proposed method matches well with that measured by an in situ buoy nearby and the simulation data. These promising results demonstrate the efficiency and accuracy of the algorithm proposed in the paper. 展开更多
关键词 X-band radar optical flow weighted average ocean wave direction radar image
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An improved optical flow method to estimate Arctic sea ice velocity(winter 2014-2016)
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作者 Haili Li Changqing Ke +2 位作者 Qinghui Zhu Xiaoyi Shen Mengmeng Li 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2021年第12期148-160,共13页
Sea ice velocity impacts the distribution of sea ice,and the flux of exported sea ice through the Fram Strait increases with increasing ice velocity.Therefore,improving the accuracy of estimates of the sea ice velocit... Sea ice velocity impacts the distribution of sea ice,and the flux of exported sea ice through the Fram Strait increases with increasing ice velocity.Therefore,improving the accuracy of estimates of the sea ice velocity is important.We introduce a pyramid algorithm into the Horn-Schunck optical flow(HS-OF)method(to develop the PHS-OF method).Before calculating the sea ice velocity,we generate multilayer pyramid images from an original brightness temperature image.Then,the sea ice velocity of the pyramid layer is calculated,and the ice velocity in the original image is calculated by layer iteration.Winter Arctic sea ice velocities from 2014 to 2016 are obtained and used to discuss the accuracy of the HS-OF method and PHS-OF(specifically the 2-layer PHS-OF(2 LPHS-OF)and 4-layer PHS-OF(4 LPHS-OF))methods.The results prove that the PHS-OF method indeed improves the accuracy of sea ice velocity estimates,and the 2 LPHS-OF scheme is more appropriate for estimating ice velocity.The error is smaller for the 2 LPHS-OF velocity estimates than values from the Ocean and Sea Ice Satellite Application Facility and the Copernicus Marine Environment Monitoring Service,and estimates of changes in velocity by the 2 LPHS-OF method are consistent with those from the National Snow and Ice Data Center.Sea ice undergoes two main motion patterns,i.e.,transpolar drift and the Beaufort Gyre.In addition,cyclonic and anticyclonic ice drift occurred during winter 2016.Variations in sea ice velocity are related to the open water area,sea ice retreat time and length of the open water season. 展开更多
关键词 winter sea ice velocity pyramid Horn-Schunck optical flow(PHS-OF)method transpolar drift Beaufort Gyre open water Arctic
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Optical flow-based method to estimate internal wave parameters from X-band marine radar images
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作者 Jinghan Wen Zhongbiao Chen Yijun He 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2022年第9期149-157,共9页
The velocity and direction of internal waves(IWs) are important parameters of the ocean,however,traditional observation methods can only obtain the average parameters of IWs for a single location or large area.Herein,... The velocity and direction of internal waves(IWs) are important parameters of the ocean,however,traditional observation methods can only obtain the average parameters of IWs for a single location or large area.Herein,a new method based on optical flow is proposed to derive the phase velocity vectors of IWs from X-band marine radar images.First,the X-band marine radar image sequence is averaged,and ramp correction is used to reduce the attenuation of gray values with increasing radial range.Second,the average propagation direction of the IWs is determined using the two-dimensional Fourier transform of the radar images;two radial profiles along this direction are selected from two adjacent radar images;and then,the average phase velocity of the IWs is estimated from these radial profiles.Third,the averaged radar images are processed via histogram equalization and binarization to reduce the influence of noise on the radar images.Fourth,a weighting factor is determined using the average phase velocity of a reference point;the phase velocities on the wave crest of the IWs are subsequently estimated via the optical flow method.Finally,the proposed method is validated using X-band marine radar image sequences observed on an oil platform in the South China Sea,and the error of the phase velocity is calculated to be 0.000 3–0.073 8 m/s.The application conditions of the proposed method are also discussed using two different types of IW packets. 展开更多
关键词 internal wave X-band marine radar optical flow phase velocity
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Comparision of DdQm models in image optical flow analysis based on LBM
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作者 丁广太 徐加银 李超 《Journal of Shanghai University(English Edition)》 CAS 2011年第5期363-368,共6页
The optical flow analysis of the image sequence based on the formal lattice Boltzmann equation, with different DdQm models, is discussed in this paper. The Mgorithm is based on the lattice Boltzmann method (LBM), wh... The optical flow analysis of the image sequence based on the formal lattice Boltzmann equation, with different DdQm models, is discussed in this paper. The Mgorithm is based on the lattice Boltzmann method (LBM), which is used in computational fluid dynamics theory for the simulation of fluid dynamics. At first, a generalized approximation to the formal lattice Boltzmann equation is discussed. Then the effects of different DdQm models on the results of the optical flow estimation are compared with each other, while calculating the movement vectors of pixels in the image sequence. The experimental results show that the higher dimension DdQm models, e.g., D3Q15 are more effective than those lower dimension ones. 展开更多
关键词 optical flow constraint image sequence the formal lattice Boltzmann equation DdQm model Lucas and Kanade's method Horn and Schunck's method.
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Vision-Based Obstacle Avoidance in Sidewalk Environment Using Top-View Transform and Optical-Flow
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作者 Young-jun HAN Hern-soo HAHN 《Journal of Measurement Science and Instrumentation》 CAS 2011年第4期341-345,共5页
This paper presents a vision-based obstacle avoidance method for blind pedestrians in an outdoor sidewalk environ- ment. Unlike many existing travel-aid systems using stereo-vi- sion based methods, the proposed method... This paper presents a vision-based obstacle avoidance method for blind pedestrians in an outdoor sidewalk environ- ment. Unlike many existing travel-aid systems using stereo-vi- sion based methods, the proposed method is able to get obstacle position as well as user motion information by just one monocu- lar camera fixed at the belly of the user. To achieve this goal, a top-view transformation of the road image is used for obstacle detection and user motion estimation, based on which a grid map is generated for navigation. For detection part, the bottom points of erect obstacles are detected by extracting local-maxima and minima on the top-view image while user motion is estimat- ed by analysing the optical flow vector field in the user sur- rounding area. For the obstacle avoidance part, a step score is calculated on the grid map for evaluating the safety of next moving step. Experiments with several sidewalk video-clips show that the proposed obstacle avoidance method is able to provide useful guidance instructions under certain sidewalk environments. 展开更多
关键词 electronic travel aids obstacle avoidance top-viewtransform optical flow
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