Hongmei Zhang

Study on side scan sonar image matching based on the integration of SURF and similarity calculation of typical areas

In this paper, a method for side scan sonar image matching is proposed based on SURF and similarity calculating in typical areas. The process is composed of three steps of rough matching, geometric correction and accurate matching. Firstly, rough matching is implemented to get a rough matching relationship of reference image and matching image based on SURF. Then geometric correction is executed with the relationship to make the matching image have a same viewing condition with the reference image. Finally, accurate matching is implemented by similarity calculating of typical areas in two corrected images. This matching algorithm combined the merits of the regional matching and feature matching. Experiment proved that the method has advantages in speed, accuracy, reliability and invariance to geometric differences between two side scan sonar images.

Design of digital filter based on VB and matlab

The core of digital signal processing is the design of digital filter. At present, most digital filters are designed by Matlab, which is a high-performance numerical calculation software and provides a powerful function of graphical display. Matlab is widely used in engineering calculation, numerical analysis and other fields, but it is less able to develop interface. In this paper, a method of hybrid programming with VB and Matlab is introduced to design digital filter. The integrated software can take full advantages of VB and Matlab, and the process of realization indicates that this method is simple and convenient.

Study on establishing local marine geomagnetic field model

Establishment local marine geomagnetic field model with marine geomagnetic observation is very important for marine research and exploration. Four methods, which are Taylor polynomial, Legendre polynomial, spline surface function and multi-surface function, are introduced into the work. Some key problems in the establishment of the model by the four methods are studied and discussed in the paper. In order to further improve the modeling accuracies of the four methods, zoning modeling is also studied and given out. Integrated the above researches, an optimum method, multi-surface function with zoning modeling, is presented by comparing and analyzing the four methods in actual applications, which achieves the model accuracy better than 5 nT in establishing local marine geomagnetic field finally.

Study on underwater terrain matching positioning based on the integration of TERCOM and MCTM

Based on the current situation of underwater navigation, this paper presents an underwater topographic matching navigation method which is the integration of TERCOM and MCTM algorithm. First of all, we use the TERCOM to acquire a rough position of vehicle. Secondly, a search area is found according to TERCOM positioning result. The multi-contour matching algorithm is implemented in the area. The algorithm is based on the chain code. By means of the code technique, all of contours are coded. Then, each contour coded in the real-time terrain is matched with the corresponding background one. Each matched contour can provide a set of transformation parameters between the real-time terrain and the background. According to all of the transformation parameters acquired from different contour matches, a weighted average is adopted so as to acquire the accurate transformation parameters. Finally, By means of the final transformation parameters, the actual location of underwater vehicle is given out.

Design of optimum filter for blend of GPS height and heave

Precise determination of transducer instantaneous height of multibeam bathymetric system (MBS) is a very important work in fulfilling the transformation from the MBS sounding data to the underwater topographic height. The blend of GPS height and heave can get accurately the solution. But it is a key to design an optimum filter for implementing the blend. In this paper, we study in detail the method of designing optimum filter for the blend. Firstly, we analyze the frequency-spectrum characters of GPS height signal, heave signal and tidal level. Secondly, we choose Fast Fourier Transform (FFT) as an optimization filter design method for the extraction and blend of the valid signals. Thirdly, by analyzing the frequency-band distributions of GPS height signal and heave signal, we give out the appropriate cut-off frequency as 1/10 Hz in the signal blend. Based on above research, we blend the low-frequency signal from GPS height and the high-frequency signal from heave. Finally, the research was tested and proved by an actual project. An underwater topographic accuracy better than 10 centimeters was achieved by the research with MBS.

Study on underwater synthetic navigation system based on inertial navigation system and multibeam bathymetric system

Inertial navigation system (INS) is an independent navigation system, but is difficult to be used in far-distance and long-time navigation due to INS accumulation error. Thus, a new synthetic navigation system for underwater based on the integration of INS and multibeam bathymetric system (MBS) is studied and presented in the paper. Firstly, we introduce the composition of the underwater navigation system and the functions of each unit in the system. Secondly, we introduce the work principle of the integrated system. Thirdly, a complete navigation and positioning algorithm based on contour match is studied deeply. In the work, first of all, we study the method of drawing contours with MBS bathymetric data. Then by means of image matching technique, we study a fast image matching algorithm based on wavelet transformation and sequential similarity detection algorithm (SSDA). According to above work, we fulfill the contour match and the determination of underwater vehicle. In order to test the integrated system, an experiment is implemented with observed MBS data and simulated INS data finally. The experimental result proves that the system has high navigation and positioning accuracy, as well as credibility and stability.

Integrated underwater navigation system based on INS and SSS

Based on analyzing current independent navigation methods, this paper presents a new underwater navigation system, which is integrated inertial navigation system (INS) and side scan sonar (SSS). Firstly we introduce the component of the underwater navigation system and the functions of each unit in the system. Then, we study the algorithm of the matching navigation used in the system. A fast image match method by integrating wavelet transform and improved sequential similarity detection algorithm (SSDA) is given out. Based on above researches, we implement simulation experiments. Experimental results show that the system presented in this paper can acquire high navigation accuracy under the background with characteristic seabed relief. Finally, some valuable conclusions and suggestions are given.