Research On Precise GPS Positioning Of Single Frequency

After decades of development, GPS has been applied to many fields like navigation,satellite orbiting, positioning, navigation state monitoring and geodetics. GPS has been anessential part of industry, researching and education. Positioning with single frequencyrequires less capability of the receiver, as a result, the cost can be reduced. Positioningalgorithms with single frequency is studied, and a piece of carrier-phase data processingsoftware is developed.In the paper, firstly the GPS observables, physical influences, coordinate and time systemare studied. GPS observables include code pseudoranges, carrier phases and Dopplermeasurements. Pseudorange is the measurement of the distance between satellite and receiver.Carrier phase is the related value between the satellite signal and receiver frequency.Physical influences of GPS observations like ionospheric effects and multi-path effects areintroduced. Ionospheric effects can be eliminated by certain model.Secondly, model for GPS positioning and algorithms for ambiguity resolutions are studied.There are functional model and stochastic model for GPS positonging. Double differencefuction model is discussed, in which ionospheric effects, tropospheric effects, clock errors andother influences are largely eliminated. Integer least square method and LAMBDA methodwhich based on ILS are discussed. Because GPS ambiguities in double difference are largelycorrelated, the admmissable transformation methods for ambiguity decorrelation are dissussedwhich includes the two dimensional integer transformation and the multi-dimensionaltransformation method.The cycle-slip detection and repair is one of the core questions in the GPS data processingand the precondition of obtaining high precision positioning and navigation results. Thecomputational procedures of ionosphere residual error, wavelet transform and Kalmanfiltering for cycle-slip detection and repair are proposed and described. Analysis andconclusions are given through examples with real GPS data. Practical function for eachmethod are discussed and compared. Conclutions are drew from the discussions.Kalmanfiltering method is chosen with attention to the practical performance for engineeringapplications.Finally, a piece of software of GPS carrier-phase double difference data processing isdesigned and developed. The computing result of real GPS data are analysed.