Ultra-wideband (UWB) time-of-flight (TOF)-based ranging information in a non-line-of-sight (NLOS) environment can display significant forward errors, which directly affect positioning performance. NLOS has been a major factor limiting the improvement of UWB positioning accuracy and its application in complex scenarios. Therefore, in order to weaken the influence of the indoor complex environment on the NLOS environment of UWB and to further improve the performance of positioning, in this paper, we first analyze the factors and characteristics of NLOS formation in an indoor environment. The NLOS is divided into fixed NLOS influenced by spatial structure and dynamic random NLOS influenced by human occlusion. Then, the anchor LOS/NLOS information map is established by making full use of indoor spatial a priori information. On this basis, a robust adaptive extended Kalman filtering algorithm based on the anchor LOS/NLOS information map is designed, which is not only effectively able to exclude the influence of spatial NLOS, but can also optimize the random error. The proposed algorithm was validated in different experimental scenarios. The experimental results show that the positioning accuracy is better than 0.32 m in complex indoor NLOS environments.
The ionospheric morphology responses to tropical cyclone passing over eastern Australia, named as Debbie in 2017, is investigated using Global Positioning System (GPS) Slant Total Electron Content (STEC), and ionospheric characteristics by ionosonde. Based on the data analysis in this study, some significant morphological characteristics of ionospheric responses to tropical cyclone Debbie are identified as follows. As the GPS satellites PRN05 and PRN20 observed on Townsville GPS station were passing near to the cyclone Debbie center at landfall time, their STEC values are obviously increased. The stronger enhancement of f0F1 and f0F2 were also observed by ionosonde at Townsville on 28th March, when the distance between Townsville and the center of tropical cyclone Debbie was shorter. Regarding the coupling mechanism between the ionospheric disturbance and the tropical cyclone, it is supposed that the electric field perturbations due to turbulent top movement from tropical cyclones might generate ionospheric irregularity and disturbance.
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