3DMA GNSS Positioning with Multipath Signals in Urban Areas: Methodology and Preliminary Results

3D Mapping Aided (3DMA) GNSS has emerged as a promising solution to enhance the performance of GNSS in urban areas. The basic idea of 3DMA GNSS positioning is to compare simulated and observed GNSS signal characteristics and find the best matching location. 3D mapping data is utilized to simulate the features of GNSS signals observed, such as satellite visibility (shadow matching) and pseudorange value (raytracing), under obstruction and reflection from urban buildings. Due to the difficulty in effectively simulating the characteristics of multipath signals, current 3DMA GNSS methods generally exclude the observations from multipath reception. However, ignoring multipath satellites will not only reduce the number of available GNSS observations but also result in valuable signal propagation characteristics contained in multipath signals going unexploited. In this paper, a novel 3DMA GNSS positioning method focusing on the utilization of multipath signals in urban areas is proposed. GNSS Interferometric Reflectometry (GNSS-IR) is introduced to estimate the perpendicular distance between a GNSS receiver and surrounding reflective building facades using SNR observations from multipath satellites. The estimated distances can be simulated based on 3D mapping data and compared, and the best matching point is determined as the receiver's position. Two static positioning experiments were conducted using smartphones in different urban environments to verify the performance of the proposed method. The results show that the positioning error of the proposed method is less than 3 m in both scenarios, improving the accuracy by more than 70% compared to traditional methods.