Research On Positioning Algorithm Based On Single-frequency Low-cost Receiver

With the rapid development of the Global Navigation Satellites System(GNSS),various positioning modes of GNSS have been widely used.Due to the advantages of low price and small size of single-frequency low-cost receivers,they are widely used in car navigation,precision agriculture and other industries.At the same time,the pseudorange observations of single-frequency low-cost receivers will have a large noise error error.Phase smoothing pseudorange can reduce the impact of measurement noise on positioning results,but carrier phase smoothing pseudorange technology is limited by smooth The size of the window,the quality control of the pseudorange and carrier phase observations,such as the gross difference between the pseudorange and carrier phase,the cycle slip,and the accumulated ionospheric residuals of adjacent epochs may cause the smoothing filter to diverge.Therefore,this paper conducts algorithm research on the above difficult problems,the main research is as follows:(1)In order to solve the problem of the cumulative amount of ionospheric changes in the carrier phase smoothing pseudorange,the optimal smoothing window is determined according to the ionospheric change rate and observation noise.A method for determining observation noise suitable for single frequency receivers is proposed.And verify the effectiveness of this method in low-cost receivers.(2)In view of the problems in the quality of observation data of low-cost receivers,the carrier phase smoothing pseudorange algorithm is introduced into quality control conditions to mitigate the effects of accumulated ionospheric errors,cycle slips and gross errors.At the same time,the state update is combined with single-difference Hatch filtering and Kalman filtering.The results show that using this method for lowcost receiver positioning,the accuracy is significantly improved compared to pseudorange single-point positioning,traditional Hatch filtering and pseudorange double-difference relative positioning.(3)RTK performance evaluation of static and dynamic experiments of Ublox single frequency low cost receiver.The results show that in the static experiment,the positioning accuracy in the open plane direction is 0.16 m and the vertical positioning accuracy is achieved in the vertical direction.In the occlusion environment,the submeter positioning accuracy is achieved in the planar direction and the sub-decimeter positioning accuracy is achieved in the vertical direction.Dynamic experiment: In the open environment,the sub-meter accuracy is achieved in the planar direction and the positioning accuracy in the vertical direction is 0.47 m.In the occlusion environment,sub-meter positioning accuracy can be achieved on the plane,and meter-level positioning accuracy can be achieved in the vertical direction.(4)Based on the VS2013 platform using C language,the GNSS multi-system combined RTK positioning software was developed,and its stability was tested with measured data.The results show that the software is stable and reliable.