Research On Indoor Positioning Method Based On Geomagnetic Field

With the acceleration of the modernization process,people's demand for Location-Based Services(LBS)is no longer satisfied with the outdoor environment,and the demand for Location-Based Indoor Location Services(ILBS)becomes more urgent.Indoor Positioning Systems(IPS)are designed to provide information about the location of people or objects in the building.With the rapid development of Internet of Things(IOT)technology in recent years,more and more scholars provide their own solutions for IPS.Among many solutions,geomagnetic positioning method is popular because of its low cost and high precision.In this method,the magnetic map is constructed by pre forming the magnetic fingerprint for the indoor environment,and then the real-time data is matched with the fingerprint data in the magnetic map in the positioning stage to achieve the positioning function.However,in the current research,there are many problems,such as low resolution of magnetic fingerprint,time-consuming and labor-consuming of magnetic map construction,and insufficient optimization of location algorithm.To solve the above problems,this paper proposes an indoor geomagnetic positioning method based on Android smart phone.The specific work includes the following aspects:1.Aiming at the problem that the complementary filter is obviously affected by the change of magnetic field in indoor environment,this paper improves the complementary filter and proposes an improved complementary filter algorithm.The algorithm makes full use of the high accuracy of gyroscope in a short period of time,projects the measured magnetic field into the geographical coordinate system,and then compares it with the local standard magnetic field,so as to dynamically change the filtering coefficient.2.Aiming at the problem that the number of magnetic fingerprint features in magnetic map is less,this paper proposes a method of generating and extracting magnetic fingerprint.Firstly,the improved complementary filtering algorithm is used to calculate the mobile phone's attitude and obtain the mobile phone's attitude matrix.Then the attitude matrix is used to transform the collected magnetic field data from carrier coordinate system to geographic coordinate system.At last,the magnetic fingerprint data of the current position is extracted from the conversion results,so as to obtain the accurate three-dimensional characteristics of the magnetic field.3.In view of the time-consuming and labor-consuming problem of magnetic map construction at present,this paper proposes a fast construction method of magnetic map.The indoor environment is divided into a set of straight-line paths,and then the magnetic fingerprint of each path is obtained by the proposed method of magnetic fingerprint generation and extraction.Finally,the magnetic map is constructed by interpolation algorithm,which improves the efficiency of the map construction.4.Aiming at the problem of low positioning accuracy caused by low resolution of indoor magnetic field,this paper improves the gait detection algorithm based on accelerometer,and takes the output result as the state model of Particle Filtering(PF)algorithm,and realizes the optimal positioning algorithm combining PDR and PF.In addition,the test client is designed,and the positioning method proposed is tested by modularization test and overall positioning test.The results show that the indoor geomagnetic positioning method proposed in this paper can achieve positioning accuracy within 0.7m,which can meet the basic requirements of indoor positioning.