Gyrocompass System Study For Vessel Attitude Determination Utilizing Global Positioning System

GPS gyrocompass is a crucial instrument used in navigation and attitude determination aspects. It has many advantages such as little volume, high precision, convenient, uninfluenced by magnetic field and no errors accumulation and so on. An essential trend is noticed that GPS gyrocompass will replace the traditional compass in some applications. Low-cost direction determination for civil ship has long been an issue of great interest in navigation. Recently, the attitude determination study has been focused more and more in the application of GPS study. The main idea of this method is to calculate the attitude parameters of the differencing equations by the observations received from GPS broadcast. The most important and difficult point of this technology is to find out the integer ambiguity combinations and resolve the attitude angles accurately in a short time.The main work in this paper includes the principle of attitude determination, carrier differencing method, integer ambiguity searching algorithm and attitude determination test. The major contributions and roadmap of the thesis are summarized as follows. Firstly, having a deep study and discussing about the hybrid analytical method. This method can help advance the real-time calculation and optimize the process of the searching work. Secondly, along with a length constraint of baseline, the improved algorithm can reduce the search span effectively, and this method will be important for the initialization step. Thirdly, a new method which reduces the times of restart in many different environments is discussed in the paper. The fourth one is the RAIM algorithm which is introduced to help advance the accuracy and stability of attitude results. The fifth part of the paper gives the experiment process in attitude determination. The test is carried out in the campus environment and the main equipments we used in the experiment are Super-Star II receivers and PC-104 machine. Results of this system are analyzed and compared with the traditional method in detail, while the precision of the system can be up to 0.1°to 0.2°rms around. Finally, it should be noticed that the study in this paper should not only be used on ship navigation but also could be applied to airocraft in the future.