Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have pr...Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have predominantly focused on landslides that occur on land.To this end,we aim to investigate ashore and underwater landslide data synchronously.This study proposes an optimized mosaicking method for ashore and underwater landslide data.This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area,airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud,the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries.Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method.In addition,synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images.A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods.The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.展开更多
Multi-beam Sonar and Side-scan Sonar compensate each other. In order to fully utilize all information, it is necessary to fuse two kinds of image and data. And the image co-registration is an important and complicated...Multi-beam Sonar and Side-scan Sonar compensate each other. In order to fully utilize all information, it is necessary to fuse two kinds of image and data. And the image co-registration is an important and complicated job before fusion. This paper suggests combining bathymetric data with intensity image, obtaining the characteristic points through the minimal angles of lines, and then deciding the corresponding image points by the maximal correlate coefficient in searching space. Finally, the second order polynomial is applied to the deformation model. After the images have been co-registered, Wavelet is used to fuse the images. It is shown that this algorithm can be used in the flat seafloor or the isotropic seabed. Verification is made in the paper with the observed data.展开更多
Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usual...Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usually made by machanic-clectronic components. But,there exists a fixed bias error in target tracking due to the application of discrete tapped delay line. With the development of digital sonar the multi-beamforming technique is extensively used in various sonar systems. In these systems each beam has a fixed bearing direction. The precise DOA (Direction Of Arrival) estimation of the target becomes more important in sonar design. General speaking, if the sampling frequency is high enough, it is possible to get arbitrary number of beams, which steer in any designated direction. But a hardware tradeoff must be taken account for a good designer. In order to obtain higher target spatial resolution and reduce the hardware cost, it is necessary to make some kind of interpolation algorithm in post beamforming. It is proved that in the most interested situation the behavior of directivity function in the neighborhood of main lobe depends on the sinc function and zero order Bessel function. The multi-beam data is actually the spatial sampling to these function. Based on the principle of parabolic interpolation, a simple but high accuracy beam interpolation technique is presented in this paper. The theoretical basis of three-point and five-point interpolation algorithm is described. As an example, the line array and circle array of hydrophones are illustrated to explain this algorithm. The results of system simulation show that the method proposed in this paper has good agreement with the theory. It can be used to improve the behavior of the directivity function and enhance the multi-target resolving ability of digital sonar system. It is also possible to use this technique to implement ATT (Automatic TargetTracking) in real time.展开更多
基金supported in part by the National Key R&D Program of China(Grant no.2016YFC0401908)。
文摘Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have predominantly focused on landslides that occur on land.To this end,we aim to investigate ashore and underwater landslide data synchronously.This study proposes an optimized mosaicking method for ashore and underwater landslide data.This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area,airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud,the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries.Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method.In addition,synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images.A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods.The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.
文摘Multi-beam Sonar and Side-scan Sonar compensate each other. In order to fully utilize all information, it is necessary to fuse two kinds of image and data. And the image co-registration is an important and complicated job before fusion. This paper suggests combining bathymetric data with intensity image, obtaining the characteristic points through the minimal angles of lines, and then deciding the corresponding image points by the maximal correlate coefficient in searching space. Finally, the second order polynomial is applied to the deformation model. After the images have been co-registered, Wavelet is used to fuse the images. It is shown that this algorithm can be used in the flat seafloor or the isotropic seabed. Verification is made in the paper with the observed data.
文摘Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usually made by machanic-clectronic components. But,there exists a fixed bias error in target tracking due to the application of discrete tapped delay line. With the development of digital sonar the multi-beamforming technique is extensively used in various sonar systems. In these systems each beam has a fixed bearing direction. The precise DOA (Direction Of Arrival) estimation of the target becomes more important in sonar design. General speaking, if the sampling frequency is high enough, it is possible to get arbitrary number of beams, which steer in any designated direction. But a hardware tradeoff must be taken account for a good designer. In order to obtain higher target spatial resolution and reduce the hardware cost, it is necessary to make some kind of interpolation algorithm in post beamforming. It is proved that in the most interested situation the behavior of directivity function in the neighborhood of main lobe depends on the sinc function and zero order Bessel function. The multi-beam data is actually the spatial sampling to these function. Based on the principle of parabolic interpolation, a simple but high accuracy beam interpolation technique is presented in this paper. The theoretical basis of three-point and five-point interpolation algorithm is described. As an example, the line array and circle array of hydrophones are illustrated to explain this algorithm. The results of system simulation show that the method proposed in this paper has good agreement with the theory. It can be used to improve the behavior of the directivity function and enhance the multi-target resolving ability of digital sonar system. It is also possible to use this technique to implement ATT (Automatic TargetTracking) in real time.
