Research On The Position Method Based On U-blox Module

With the development of A-GPS positioning technology,low-cost positioning chips are widely used on portable carriers,such as mobile phones,tablet computers,and car navigation systems,and have broad application prospects.However,the positioning performance of low-cost navigation modules is far inferior to that of measurement receivers.The specific performance is that the observation noise is large,the positioning accuracy is poor,and the stability is not high.This paper chooses u-blox NEO M8T navigation module as the research object,uses pseudorange,carrier phase,doppler and SNR,studies from the perspective of reducing the noise of original observations and gross error.The main contents are as follows:1?Study the encoding rules of the original observation data in the UBX protocol,and complete the decoding of the observation value file and the navigation message file.Analyze the original positioning accuracy,the number of the search satellites and the signal quality of the u-blox NEO M8T module.Evaluate the performance of u-blox module systematically with the cost performance,sensitivity and time to first fix.2?Analyze the relationship between height angle,SNR and GPS observations quality,design a fast select satellites method based on SNR,and study the influence of different weighting random models on positioning accuracy.The experimental results show that the weighting method of using SNR-elevation combined stochastic model can better suppress observation noise and gross error.Compare with the weighting method that only uses the elevation stochastic model and the SNR stochastic model,the precision of inner coincidence and and the precision are greatly improved.3?Analyze the measurement accuracy of doppler and carrier phase,set the reasonable smoothing duration,and use doppler to smooth the pseudoranges replace the carrier phase difference components,it's better to solve the problem of carrier phase observations are easy to have cycle slip in the complex environment and gradual accumulation of ionospheric delay variation during smooth pseudoranges.The experimental results show that the measurement accuracy of doppler can reach centimeter level,and the stability is higher.Use doppler smooth pseudorange positioning,the positioning accuracy and stability of u-blox module can be further improved on the basis of satellites selection and weighting,its dynamic positioning accuracy in the N/E/U direction increased by 28.6%,9.1%,and 4.6%,respectively.