Experimental Investigation of GNSS Direct Position Estimation in Densely Urban Area

Direct Position Estimation (DPE) has been introduced as a robust global navigation satellite system (GNSS) positioning method. Its superior performance stems from the full coupling of visible satellites. Previous literature has established that DPE offers more robust positioning against the conventional two-step scalar tracking loop (STL) receiver. However, its performance has yet to be evaluated under real urban environments. This paper aims to evaluate DPE performance with large-scale field tests. GNSS datasets were collected in various urban environments in Hong Kong, and the performance of DPE was compared with STL. Results have shown that DPE is superior when the satellite’s correlation values converge at the true receiver position, commonly occurring in light urban areas, where the majority of satellites are line-of-sight (LOS). But when satellites are severely affected by Multipath (MP) and non-line-of-sight (NLOS) errors, their correlation values deviate from the true user position. This paper finds that DPE’s outperformance against STL falters with an increasing number of deviated correlation values. This effect is further compounded by poor satellite geometry, together with the widening of correlation values due to MP reception. This conclusion is further supported by simulation results.