Research On Information Disposed Module Of A GPS-based Marine Navigation System

In this paper, information disposed module of a marine navigation system based on GPS are investigated and completed .The function of the module is to calculate navigation information for marine navigation system. The module's software is designed in Visual C++ develop environment. The design of this module's software divides into three parts. The first part is to receive the orientation information from COM port connected with GPS-OEM board. The second part is to pick up longitude, latitude, velocity and time data from orientation information according to data format. The last part is to calculate navigation parameter based on known sea route information and orientation information. The module's key technique is described in detail in this paper. One is the design of navigation parameter arithmetic. In the past the big circular navigation method was used. This method considers the earth 's shape as a global shape so it's precision is not good. In this paper, the earth 's shape is considered as ellipse .So the method of normal intercept arc is used to calculate earth-line-length and azimuth angle. The precision of this method is better than past. The calculation formula of leeway angle and leeway distance becomes simple because of using this method. The other key is the design of interface of this module. The interface includes three parts as follows: the interface to GPS-OEM board; the interface to interface module; the interface to track manage module. The criterion of interface , data frame and data structure are designed in detail. Furthermore, the method of receiving data from COM port is designed too. By using of multithreading technique, the data transmission is fulfilled between GPS receiver and computer. The process runs in background. This method adapts to serial communication in any way and can provide some users for reference. The information disposed module of a marine navigation system runs well by test. The functions preplanned are completed. The precision of navigation parameter is satisfied with our need.