Enabling High Accuracy Dynamic Applications in Urban Environments Using PPP and RTK on Android Multi-Frequency and Multi-GNSS Smartphones

摘要

In recent months, smartphones and IoT devices have become the leading products of mass-market GNSS. However, they are still limited in their positioning capability and, even with the release of Android raw measurements in late 2016, the use of PPP and RTK processing is still yet to be optimised. Smartphones are not ideal GNSS receivers, their measurements suffer from interference and multipath effects due to the multi-purpose nature of the antenna, shared with other systems such as Wi-Fi and Bluetooth. The Xiaomi Mi 8 represented a milestone within the GNSS mass-market, offering improved accuracies with the multi-frequency GNSS Broadcom BCM47755 chipset. The additional L5/E5 signals improve the resilience, but not immunity, to multipath effects in urban environments. This work is completed through the FLAMINGO initiative (Fulfilling enhanced Location Accuracy in the Mass-market through Initial GalileO services) which endeavours to facilitate mass-market devices to achieve sub-metre accuracies by using raw GNSS measurements and advances in GNSS hardware, systems and infrastructure. The PPP and RTK accuracies achievable in urban areas are evaluated through a field test within a varied semi-open sky and sub-urban environment. Objects have been identified with a FLAMINGO target accuracy, allowing evaluation of the positioning accuracy achievable in variious test scenarios. The results obtained highlight the sensitivity of the smartphone to multipath effects, especially in the sub-urban scenario. Furthermore, the use of L5/E5 observations increases the final accuracy, but the use of an ionosphere-free combination does not always provide the best results due to increased noise.