A Contour Matching Algorithm to Reconstruct Ruptured Documents

Author(s):  
Anke Stieber ◽  
Jan Schneider ◽  
Bertram Nickolay ◽  
Jörg Krüger
2011 ◽  
Vol 383-390 ◽  
pp. 7576-7581 ◽  
Author(s):  
Ya Jie Liu ◽  
Yan Zhao ◽  
Fa Lin Wu

The accumulation course angle error of inertial navigation system will decrease the accuracy and reliability of an geomagnetism aided inertial navigation system using a geomagnetic contour matching algorithm. To improve the matching accuracy, the matching track and true track should be as parallel as possible. An improved geomagnetic matching algorithm is presented by introducing rotation angle search technique. To reduce the computation burden, improve operation efficiency and reduce false matching probability, a new search area determination method is proposed, which redefines the search region and reduces the search range. Simulation results demonstrate the effectiveness of the proposed algorithm and the improvement in the matching accuracy.


2021 ◽  
Vol 13 (22) ◽  
pp. 4616
Author(s):  
Shijie Zhao ◽  
Wei Zheng ◽  
Zhaowei Li ◽  
Aigong Xu ◽  
Huizhong Zhu

In this study, we improve the matching accuracy of underwater gravity matching navigation. Firstly, the Iterative Optimal Annulus Point (IOAP) method with a novel grid topology is proposed for breaking through the inherent grid structure limit of the canonical gravity matching algorithm and enhancing its underwater gravity matching accuracy. The theory of IOAP is as follows: (1) small-annulus matching and positioning mechanism on the tracking starting point is developed by employing the starting point and drift error of the INS (Inertial Navigation System), the fixed rotation angle, etc. The optimal matching location of the starting point is obtained by matching and comparing the matched points in this small-annulus grid, which contributes to heightening the initial-position error insensitivity of the algorithms. (2) Variable-angle three-layer annulus matching and positioning mechanisms on the tracking ending point were constructed by using the optimal matching location of the starting point and combining the tracking direction-and-distance information of the INS and the cumulative drift error, etc. It is used to generate the annulus matching points with the ring-type grid topology. (3) The optimal matching position of the ending point in this annulus is obtained by iteratively calculating the evaluation index value of the matching points and following the evaluation index optimal rule. Secondly, we comprehensively consider the main performance evaluation indexes of the underwater gravity matching algorithms, such as the statistical indicators of the matching accuracy, the average matching time and the matching success rate, and take them as a basis of the pros and cons of the matching analysis. Furthermore, under conditions that include different scale searching regions or different reference-angle ring radii, the statistical results verify that the IOAP had a different matching ability and better robustness. Finally, several trajectories with the starting points from different areas and the ending points in different gravity ranges are tested and compared to carry out the numerical simulations. These results indicate that the IOAP has many advantages, such as a high matching accuracy and strong positioning applicability in different gravity regions. Compared with the TERCOM (terrain contour matching algorithm), its average matching accuracy was the highest, increased by 40.39%.


2011 ◽  
Vol 137 ◽  
pp. 128-133
Author(s):  
Yun Fang Chen ◽  
Ruo Fei Zhong ◽  
Bo Shi

Marine gravity aided INS navigation, in which Gravity anomaly and gravity gradient of earth gravity field from sensors sensitive to gravity have been supplementary information aided to correct positioning error accumulated with time to achieve precise navigation and graphic trace, has been a fervent and frontier issue in underwater passive navigation technology in application to Autonomous Underwater Vehicle (AUV). Core theoretical technology of gravity aided INS navigation was matching algorithm, in which Terrain Contour Matching (TERCOM), Sandia Inertial Terrain Aided Navigation (SITAN) and Iterative Closest Contour Point (ICCP) were three typical representatives based on gravity reference map. However, these algorithms more or less had some limitations in certain conditions such as a relatively larger INS positioning error. Aiming at the application limitation that positioning error from INS were commonly large when after a long voyage AUVs entered into the region in which gravity could be used to matching, above three algorithms were integrated to use on base of expounding their algorithm models, computation progress and advantages and disadvantages analysis, then integration theory, algorithm design and model foundation were presented to meet practice application demand better.


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