Hole repair processing is an important part of point cloud data processing in airborne 3-dimensional(3D)laser scanning technology.Due to the fragmentation and irregularity of the surface morphology,when applying the 3...Hole repair processing is an important part of point cloud data processing in airborne 3-dimensional(3D)laser scanning technology.Due to the fragmentation and irregularity of the surface morphology,when applying the 3D laser scanning technology to mountain mapping,the conventional mathematical cloud-based point cloud hole repair method is not ideal in practical applications.In order to solve this problem,we propose to repair the valley and ridge line first,and then repair the point cloud hole.The main technical steps of the method include the following points:First,the valley and ridge feature lines are extracted by the GIS slope analysis method;Then,the valley and ridge line missing from the hole are repaired by the mathematical interpolation method,and the repaired results are edited and inserted to the original point cloud;Finally,the traditional repair method is used to repair the point cloud hole whose valley line and ridge line have been repaired.Three experiments were designed and implemented in the east bank of the Xiaobaini River to test the performance of the proposed method.The results showed that compared with the direct point cloud hole repair method in Geomagic Studio software,the average repair accuracy of the proposed method,in the 16 m buffer zone of valley line and ridge line,is increased from 56.31 cm to 31.49 cm.The repair performance is significantly improved.展开更多
The analysis of the radiated noise of vessels given in this paper shows some strong superposed line components in low frequency spectrum below 100Hz occurring at discrete frequencies which correspond with the rotation...The analysis of the radiated noise of vessels given in this paper shows some strong superposed line components in low frequency spectrum below 100Hz occurring at discrete frequencies which correspond with the rotation speed of propeller shaft, or propeller blade frequency, or their harmonic frequencies. Since the line components reflect propeller's working characteristics, the propller's features can be extracted directly from low-frequency line components in addition to demodulated line component. So there are two ways to extract the features, one is direct way, the other is demodulation way. Detection performance of the line component in background-noise is discussed in this paper. The signal level is defined as the difference between the PDF's (Probability Density Function) mean of the peak of the line component and PDF's mean of the background-noise. In direct way the signal level of the line component is proportional to the signal noise ratio (S / N). In demodulation way the signal level of demodulated line component reduces with S / N descent, but the signal level reduces slowly if S / N is high and very fast if S / N is low.展开更多
The properties of 1(1/2)-spectrum are proved and the performances are an- alyzed. By means of the spectrum, the basic frequency component of the harmonic signals can be enhanced. Gaussian color noise and symetrical di...The properties of 1(1/2)-spectrum are proved and the performances are an- alyzed. By means of the spectrum, the basic frequency component of the harmonic signals can be enhanced. Gaussian color noise and symetrical distribution noise can be canceled. And non-quadratic phase coupling harmonic components in harmonic signal can be reduced. The ship radiated-noise is analyzed and its 7 features are extracted by the spectrum. By means of B-P artificial neural network, three type ships are classified according to extracted features. The classification results about the three type ships A, B and C are 90%, 91.3% and 85.7%. respectively.展开更多
基金National Natural Science Foundation of China(Nos.41861054,41371423,61966010)National Key R&D Program of China(No.2016YFB0502105)。
文摘Hole repair processing is an important part of point cloud data processing in airborne 3-dimensional(3D)laser scanning technology.Due to the fragmentation and irregularity of the surface morphology,when applying the 3D laser scanning technology to mountain mapping,the conventional mathematical cloud-based point cloud hole repair method is not ideal in practical applications.In order to solve this problem,we propose to repair the valley and ridge line first,and then repair the point cloud hole.The main technical steps of the method include the following points:First,the valley and ridge feature lines are extracted by the GIS slope analysis method;Then,the valley and ridge line missing from the hole are repaired by the mathematical interpolation method,and the repaired results are edited and inserted to the original point cloud;Finally,the traditional repair method is used to repair the point cloud hole whose valley line and ridge line have been repaired.Three experiments were designed and implemented in the east bank of the Xiaobaini River to test the performance of the proposed method.The results showed that compared with the direct point cloud hole repair method in Geomagic Studio software,the average repair accuracy of the proposed method,in the 16 m buffer zone of valley line and ridge line,is increased from 56.31 cm to 31.49 cm.The repair performance is significantly improved.
文摘The analysis of the radiated noise of vessels given in this paper shows some strong superposed line components in low frequency spectrum below 100Hz occurring at discrete frequencies which correspond with the rotation speed of propeller shaft, or propeller blade frequency, or their harmonic frequencies. Since the line components reflect propeller's working characteristics, the propller's features can be extracted directly from low-frequency line components in addition to demodulated line component. So there are two ways to extract the features, one is direct way, the other is demodulation way. Detection performance of the line component in background-noise is discussed in this paper. The signal level is defined as the difference between the PDF's (Probability Density Function) mean of the peak of the line component and PDF's mean of the background-noise. In direct way the signal level of the line component is proportional to the signal noise ratio (S / N). In demodulation way the signal level of demodulated line component reduces with S / N descent, but the signal level reduces slowly if S / N is high and very fast if S / N is low.
文摘The properties of 1(1/2)-spectrum are proved and the performances are an- alyzed. By means of the spectrum, the basic frequency component of the harmonic signals can be enhanced. Gaussian color noise and symetrical distribution noise can be canceled. And non-quadratic phase coupling harmonic components in harmonic signal can be reduced. The ship radiated-noise is analyzed and its 7 features are extracted by the spectrum. By means of B-P artificial neural network, three type ships are classified according to extracted features. The classification results about the three type ships A, B and C are 90%, 91.3% and 85.7%. respectively.
