Research On High Precision Real-time Fusion Positioning And Indoor And Outdoor Switching Of Android Smartphone

In the era of internet of everything,the position of the smart phone to provide services in the majority of the user's life plays an important role in positioning accuracy 5-10 m has been unable to meet the growing user demand for high-precision positioning.This article aims to take advantage of smart phones GNSS,IMU and BLE data to further enhance the smart phone static and dynamic positioning accuracy and indoor and outdoor realize seamless handover,effectively enhance the public user experience.This article starts with the analysis of the raw data characteristics of the smartphone GNSS and IMU,constructs a GNSS/INS fusion positioning model for pedestrians and vehicle conditions,and conducts a study on seamless indoor and outdoor switching,implements a variety of algorithms on the smartphone,and tests its positioning performance.The specific research work and its conclusions are as follows:(1).Completed the characteristic analysis of the raw data of the smartphone GNSS and IMU.This article describes the interface for smartphones to use Android API to obtain GNSS,IMU and BLE data,and gives specific methods for calculating pseudoranges;The GNSS raw data is obtained by static observation at known points,and the original pseudorange,carrier phase and Doppler are analyzed using the method of quadratic difference between epochs.The results show that the carrierto-noise ratio is closely related to the data quality.Based on the characteristics of the original data of the smartphone,a robust processing model for GNSS positioning was established;The quality and characteristics of raw data of smartphone acceleration,linear acceleration,gravitational acceleration,gyroscope,magnetometer and rotation vector under static conditions are analyzed.In the first 1minute after power-on,the output of each sensor is unstable and the noise of the accelerometer is too large,and the weight needs to be reduced.(2)Completed the research on smart phone GNSS/INS high-precision fusion positioning.Established a high-precision GNSS single-point and differential positioning model based on a smart phone,and conducted dynamic and static experiments under different observation environments.The results show that in the case of better static observation,the horizontal RMSE is 0.70 m and the vertical is 1.04 m of RTK algorithm;in the case of dynamic vehicle-mounted,the RMSE horizontal is 1.27 m,and the vertical is 2.27 m in RTK.The pedestrian and vehicle-mounted GNSS/INS positioning models are modeled separately,and the pedestrian positioning model adopts the GNSS/PDR fusion model.The test results show that the model has a certain improvement effect on the positioning accuracy.One of the mobile phones can improve the positioning accuracy by 10.1%,but it depends on the recognition of the observation environment;In the vehicle-mounted situation,the fusion positioning model can ensure that the positioning error does not exceed 8m when the GNSS signal is out of lock for 10 seconds.(3)Complete the research on seamless switching between indoor and outdoor smart phones.The method of GNSS indoor and outdoor scene judgment is introduced in detail.The HMM scene judgment model is established and tested using the number of GNSS satellites and the carrier-to-noise ratio data.The results show that the recognition accuracy of the indoor and outdoor handover process is high,and the time delay is low.It only takes 1-3s to complete the scene interpretation.Established an indoor and outdoor seamless switching model based on GNSS/PDR/BLE technology.The model considers two aspects from outdoor to indoor and indoor to outdoor,and focuses on the research on the problem that GNSS positioning requires a certain initialization time from indoor to outdoor.This process uses the PDR algorithm to keep the handover stable,and when the observation environment gradually improves,the weight of the GNSS is increased accordingly.The overall switching process is relatively smooth and stable,and the horizontal RMSE is 2.56 m.(4)High precision real-time positioning APP development.This paper implements the theoretical algorithm of the application research into the Android APP,and uses the JAVA language to complete the preparation of the APP-RTKCore for high-precision real-time positioning and indoor and outdoor switching on the Android Studio platform.It realizes the visual display function of GNSS raw data analysis,GNSS high-precision positioning,GNSS/INS fusion positioning,indoor and outdoor switching,and various auxiliary function modules.