Analysis On Accuracy Of Combined GPS/BDS Single Point Positioning

Beidou system of independent operation officially used in the Asia-Pacific region, the global network has begun, the major navigation systems have accelerated the launch of the satellite, the number of navigation satellites greatly increased due to the increase of visible satellites, making multi-constellation navigation systems become more the trend in the development of GNSS. For my country, the combination of GPS and BDS positioning inevitably become the focus and hot spots, the combination of available satellite positioning to increase, reduce accidental errors and improve the accuracy of aspects of great help, and will correct the error for the various constellations selection, combination combination of various types of satellites observed values will become the key combination, because the satellite and signal quality are good and bad, so blindly satellite does not necessarily increase the accuracy of the intake, so this topic is based on GPS/BDS portfolio positioning principle, analysis combined system improvements and random ionospheric model accuracy. The main content of this paper includes the following aspects: 1. signal and structural analysis of GPS and BDS. Analysis of the structure and the GPS signal signal Compass including traditional and modern signal signal, given differences Compass system and GPS navigation message, according to Compass GPS ICD ICD files and documents, and Beidou GPS raw data is parsed, the parsed data format RENIX standard format. 2.GNSS portfolio positioning theory. Describes the spatial and temporal reference datum GPS and Beidou system, convert them to each other are described. Solving each spatial location GPS, Compass three satellites, given GNSS observations, including the carrier phase and pseudorange observations, finally locating a combination of GPS and Compass. 3.Presentation of improved ionospheric error and correct methods, GPS Step 8 coefficient Crow break model and Compass systems Crowe Boucher model, and later introduced the dual-band corrections and ionospheric grid model. For the combined system ionospheric delay correction, also proposed to improve the hatch after filtering carrier phase smoothing pseudorange approach.4.Presentation of the combined system function model and stochastic model to analyze the combined system of several stochastic models, including models such as the right to a high degree angle model, PDOP model and a posteriori method of estimating model, the accuracy and the advantages and disadvantages of several types of stochastic models when combined system positioning solver, select the appropriate stochastic models.