Research On GPS Attitude Determination Algorithm And Antenna Configuration

It is an important research field to determine the three-dimensional attitude using carrier phrase measurements of Global Positioning System(GPS). Real-time attitude determination is derived from extremely precise differential carrier phase measurements among multiple GPS antennas mounted on the vehide.This paper mainly studies something about the carrier posture measurements using GPS, and emphatically expounds the basic theory of GPS attitude measurements.In addtion the mathematical models of attitude solving algorithm based on carrier phrase measurements is deduced, followed by analysis and demonstration of the relationship between antenna configuration and attitude measurements.GPS carrier phase observable can be made up multiple linear combination models and usually the model of double difference GPS observations is applied to attitude measurements and positioning in practice because of its unique advantages. Then the most important problem comes out,which is how to resolve integer ambiguities of double difference GPS observable equations in real-time. Several resolutions of integer ambiguity are introduced in the article, which are limited to some conditions in the application, followed by LAMBDA algorithm introduced. Because the time of observation data is very short, there are high relativity among ambiguities and the search space of ambiguities becomes a extremely narrow multidimensional ellipsoid. LAMBDA algorithm overcomes such shortcomings above successfully. In LAMBDA algorithm original ambiguities are replaced firstly, then the varience-convarience matix of original ambiguities is transformed. The result is that the search space of ambiguities becomes spheriform approximately and the variences become much smaller. The search efficiency and success rate are improved greatly combining least-squares search. Because of its perfect theory system, this paper adopts LAMBDA algorithm to calculate integer ambiguities. LAMBDA algorithm is introduced in details, which include such as the float solution estimation, ambiguities decorrelating, determining the search space of integer ambiguity and so on. In order to check out LAMBDA method, it is simulated by software MATLAB 7.0. Test results show that the positioning error is less than one wavelength of carrier and the integer ambiguities can be resolved in real-time when the algorithm is applied.The article not only discusses three methods of attitude determination, but also deduces the equations. Finally, the relationship between attitude measurements and the antenna layout is discussed after calculating carrier attitude by means of direct resolution method. Research results show that the antenna configuration affects the precision of attitude measurements and the instantaneity of attitude resolution seriously.