Research On GNSS/INS Integrated Navigation Application Based On Android Mobile Phone

The high-precision location services of smart phones,tablets and other mobile intelligent terminals based on Android system have gradually become the focus of public concern,and the demand for popular high-precision location services has become increasingly strong.At present,the mainstream positioning mode of smart phones is still GNSS positioning,but there will be weak GNSS or even no GNSS signal in the complex urban environment.At this time,GNSS can not meet the requirements of accurate positioning.This paper analyzes and studies the key technologies in GNSS/ INS Integrated Navigation of Android smartphone,aiming to realize integrated positioning by using the built-in GNSS chip of smartphone and MEMS IMU sensor,and improve the positioning performance of smartphone in sheltered environment.Relevant research work and conclusions are as follows:(1)Research on pedestrian dead reckoning PDR positioning method of Android smartphone.According to the characteristics of poor stability of MEMS IMU of smart phone,an inertial navigation PDR positioning method suitable for smart phone is proposed,and the feasibility of gait detection,step estimation and heading estimation methods proposed in this paper are verified by experiments.Experiments show that the accuracy of gait detection is better than 99%,the result of step estimation is basically consistent with the real step size of pedestrians,and the result of heading estimation can be basically consistent with the real trajectory in the first period of time.On this basis,the positioning accuracy of mobile phone PDR algorithm is further given through experiments.Without external constraints,the positioning accuracy is better than 2m in short-term 10 s,which basically meets the needs of pedestrian navigation and positioning.(2)Research on real-time carrier phase differential positioning method of smart phone.Aiming at the RTCM protocol standard in differential data transmission,the differential data encoding and decoding module of smart phone is developed.On this basis,the real-time carrier phase difference is realized,and the feasibility of mobile phone carrier phase difference is verified by static and dynamic experiments.The research shows that in the static mode,the plane positioning accuracy of MP1 smartphone is 0.465 m,the elevation positioning accuracy is 0.384 m,the plane positioning accuracy of MP2 smartphone is 0.774 m and the elevation positioning accuracy is 0.711 m.In the dynamic mode,the plane positioning accuracy of MP1 smartphone is 1.127 m,the high-range positioning accuracy is1.152 m,the plane positioning accuracy of MP2 smartphone is 0.835 m and the elevation positioning accuracy is 1.037 m.(3)Research on GNSS/INS integration of Android smartphone.According to the kinematics model of pedestrians,a pedestrian based smart phone satellite inertial fusion filter is established,and the satellite inertial fusion positioning based on Android smart phone is realized.Considering that GNSS is vulnerable to environmental impact,it is proposed to independently judge the current environmental quality by calculating the average carrier noise ratio parameters of satellites,and then dynamically adjust the observation noise matrix of GNSS,so as to reduce the weight of GNSS positioning results in places with poor observation conditions.Experiments show that the smart phone RTK + PDR fusion positioning method proposed in this paper can effectively make up for the decline of the positioning accuracy of smart phone RTK in the sheltered area.In the severe sheltered environment,the plane lifting effect of smart phone RTK + PDR fusion positioning is 47.65% and42.90%,and the elevation lifting effect is 39.78% and 67.98%.(4)Develop the integrated pedestrian navigation and positioning app on Android smartphone.Taking Android studio as the development platform and Java as the development language,a pedestrian navigation and positioning app software is developed,which realizes the pedestrian dead reckoning positioning method,carrier phase differential positioning method and satellite inertial fusion positioning method on Android smartphone.It provides public users with an Android smartphone navigation and positioning app software with high positioning accuracy,good continuity and low cost.