GNSS smartphones positioning: advances, challenges, opportunities, and future perspectives

Abstract

Starting from 2016, the raw Global Navigation Satellite System (GNSS) measurements can be extracted from the Android Nougat (or later) operating systems. Since then, GNSS smartphone positioning has been given much attention. A high number of related publications indicates the importance of the research in this field, as it has been doing in recent years. Due to the cost-effectiveness of the GNSS smartphones, they can be employed in a wide variety of applications such as cadastral surveys, mapping surveying applications, vehicle and pedestrian navigation and etc. However, there are still some challenges regarding the noisy smartphone GNSS observations, the environment effect and smartphone holding modes and the algorithm development part which restrict the users to achieve high-precision smartphone positioning. In this review paper, we overview the research works carried out in this field with a focus on the following aspects: first, to provide a review of fundamental work on raw smartphone observations and quality assessment of GNSS observations from major smart devices including Google Pixel 4, Google Pixel 5, Xiaomi Mi 8 and Samsung Ultra S20 in terms of their signal strengths and carrier-phase continuities, second, to describe the current state of smartphone positioning research field until most recently in 2021 and, last, to summarize major challenges and opportunities in this filed. Finally, the paper is concluded with some remarks as well as future research perspectives.

Evaluation of Static Autonomous GNSS Positioning Accuracy Using Single-, Dual-, and Tri-Frequency Smartphones in Forest Canopy Environments

“…The trend towards higher accuracy in the mass market has become evident with the introduction of multi-constellation, multi-frequency smartphones. It will undoubtedly continue with, e.g., improvements in the new generation of GNSS chipsets and the smartphone positioning algorithms [ 49 ] or other solutions formerly intended for high-end receivers, such as RTK solutions for smartphones [ 98 ]. Therefore, there is still a need for development and research in the future.…”

“…The positioning accuracy of a GNSS module on a smartphone was typically between 3 and 5 m under good Multipath conditions and over 10 m under harsh Multipath environments [ 47 ]. However, measurements of smartphone positioning detected rapid Multipath variations over time [ 48 , 49 ]. Even when positioning was conducted using geodetic class receivers, considerable variability in positioning accuracies occurred due to the Multipath effect [ 50 ].…”

“…The additional use of the E5a/L5 frequencies is intended to reduce the Multipath effect (i.e., the reflection of satellite signals from trees, etc.) and provides the opportunity to make ionospheric-free linear combinations between observations of two frequencies to eliminate the ionosphere effect, thus improving accuracy [ 49 , 74 , 75 ]. The reception quality of the Xiaomi Mi 8, as the first dual-frequency smartphone, is particularly often studied [ 44 , 51 , 52 , 53 , 71 , 74 , 76 , 77 , 78 , 79 ].…”

Noises in Double-Differenced GNSS Observations

“…For this type of noise, the signal power spectrum is equal in all frequency bands. Identifying the type of noise allows for the determination of the noise density coefficients that are characteristic of a given noise, which can be included in the mathematical model of the observation development through the stochastic model [2,3]. Moreover, the noise is one of the coefficients that, in Kalman filtering for example, makes it possible to increase the accuracy of the position determination [4,5].…”

Relative Positioning in Remote Areas Using a GNSS Dual Frequency Smartphone

“…Other authors developed works with smartphones with other proposes, Robustelli et al [9] had done experiments to assess the observations quality and performance of GNSS standalone positioning with dual frequency smartphones, while Liu et al [10] demonstrated the impact of real-time regional ionospheric correction model can have in the smartphone positioning and Sharma et al [11] analyzed the antenna limitations in a smartphone-based GNSS positioning approaches. The authors Zangenehnejad & Gao [12] recently published a work about the opportunities and perspectives that the use of GNSS smartphones can be employed in different types of applications in the areas of mapping, navigation, cadastral, and in a wide range of works with georeferencing needs. Some of these works present results of differential positioning using very short baselines and, in general, are based on single frequency measurements, in our experiments we want to assess a long baseline survey methodology with the dual frequency.…”