Evaluation of adaptive ultra-tight integration in a forested environment

Forested environments pose a significant challenge to global navigation satellite system (GNSS) receivers with trees and foliage causing strong intermittent signal attenuation. This can cause frequent loss of lock in the tracking loops of the receiver, which in consequence can severely impact the availability and accuracy of the position, velocity, and time (PVT) solution. This paper evaluates an adaptive ultra-tight integration (UTI) tracking architecture in a hardware receiver. In this architecture, code-and carrier Doppler estimates are fed back from the PVT engine into impaired tracking channels to improve tracking robustness. The evaluation is done on real-world measurements from a test campaign in the German Black Forest. Tracking performance, PVT availability and accuracy are compared between the adaptive UTI, adaptive tracking, and non-adaptive scalar tracking as a baseline. It is shown, that the adaptive UTI significantly outperforms the non-adaptive baseline both in PVT availability and accuracy, as well as in the tracking figures of merit.