Performance Assessment of GNSS Positioning in Different Vegetated Environments

Global Navigation Satellite Systems (GNSS) can efficiently provide a user’s position, yet the accuracy of such services is highly reliant on the signal receiver’s operating environments. In urban and vegetated environments, the presence of buildings and vegetation may obstruct the sky-view of the receiver, introducing signal degradation effects such as signal attenuation, non-line-ofsight (NLOS) reception, and multipath propagation. However, the effects and the categorizations of vegetation’s influence on GNSS positioning performance remained under-covered due to their unique and sophisticated geometry. In this study, GNSS’ positioning performance, indicated by selected signal measurements, was assessed under different vegetated environments, which were categorized by specific structural parameters used in botanical research. From the result of large-scale experiments, it was found that the signal attenuation, pseudorange error, and positioning error were characterized by unique distribution patterns in the open sky, urban, and vegetated environments respectively. Further investigations demonstrates that vegetation-induced signal degradations are multipath-dominated, and that a signal from a high-elevation angle satellite would experience greater degradations. Finally, the 2D positioning error is found to be linearly and inversely correlated to the ratio of crown spread over tree height, while the 2D positioning error’s standard deviation is found to be linearly proportional to the vegetation’s sky view occupancy.