Multipath interference and non-line-of-sight (NLOS) reception are major error sources when using global navigation satellite systems (GNSS) in urban environments. A promising approach to minimize the effect of multipath interference and aid NLOS detection is vector tracking. Therefore the objective of this research is to assess vector tracking in a dense urban environment to determine its effect on multipath interference and NLOS reception. Here, a vector delay lock loop (VDLL) is implemented using an adaptive extended Kalman filter (EKF). This replaces the individual code-tracking loops and navigation filter but retains conventional carrier frequency tracking. The positioning and tracking performance of the conventional and vector tracking implementations with and without a strobe correlator are compared using intermediate frequency (IF) signals recorded in the Koto-Ku district of urban canyon Tokyo city environment. Both static and dynamic tests were performed. It is shown that vector tracking reduces the root mean square positioning error by about 30% compared to an equivalent conventional receiver in urban environments and is capable of detecting long-delay NLOS reception for a GPS receiver without any external aiding. Introduction Multipath interference and non-line of sight (NLOS) reception are major sources of error for

No abstract

Abstract-Sensors play important roles for autonomous driving.Localization is definitely a key one. Undoubtedly, global positioning system (GPS) sensor will provide absolute localization for almost all the future land vehicles. In terms of driverless car, 1.5 meters of positioning accuracy is the minimum requirement since the vehicle has to keep in a driving lane that usually wider than 3 meters. However, the skyscrapers in highly-urbanized cities such as Tokyo and Hong Kong, dramatically deteriorate GPS localization performance, leading more than 50 meters of error. GPS signals are reflected at modern glassy buildings which caused the notorious multipath effect. Fortunately, the number of navigation satellite is rapidly increasing in a global scale since the rise of multi-GNSS (global navigation satellite system). It provides an excellent opportunity for positioning algorithm developer of GPS sensor. More satellites in the sky implies more measurements to be received. Novelty, this paper proposes to take advantage of the fact that clean measurements (refers to line-of-sight measurement) are consistent and multipath measurements are inconsistent. Based on this consistency check, the faulty measurements can be detected and excluded to obtain better localization accuracy. Experimental results indicate that the proposed method can achieve less than 1 meter lateral positioning error in middle urban canyons.

The Precise Point Positioning (PPP) is a popular positioning technique that is dependent on the use of precise orbits and clock corrections. One serious problem for real-time PPP applications such as natural hazard early warning systems and hydrographic surveying is when a sudden communication break takes place resulting in a discontinuity in receiving these orbit and clock corrections for a period that may extend from a few minutes to hours. A method is presented to maintain real-time PPP with 3D accuracy less than a decimeter when such a break takes place. We focus on the open-access International GNSS Service (IGS) Real-time Service (RTS) products and propose predicting the precise orbit and clock corrections as time series. For a short corrections outage of a few minutes we predict the IGS-RTS orbits using a fourth order polynomial, and for longer outages up to 3 hrs, the most recent IGS ultra-rapid orbits are used. The IGS-RTS clock corrections are predicted using a second order polynomial and sinusoidal terms. The models parameters are estimated sequentially using a sliding time window such that they are available when needed. The prediction model of the clock correction is built based on the analysis of their properties, including their temporal behavior and stability. Evaluation of the proposed method in static and kinematic testing shows that positioning precision of less than 10 cm can be maintained for up to two hours after the break. When PPP re-initialization is needed during the break, the solution convergence time increases; however, positioning precision remains less than a decimeter after convergence.

Continuous and trustworthy positioning is a critical capability for advanced driver assistance systems (ADAS). To achieve continuous positioning, methods such as global navigation satellite systems real-time kinematic (RTK), Doppler-based positioning, and positioning using low-cost inertial measurement unit (IMU) with car speedometer data are combined in this study. To ensure reliable positioning, the system should have integrity monitoring above a certain level, such as 99%. Achieving this level when combining different types of measurements that have different characteristics and different types of errors is a challenge. In this study, a novel integrity monitoring approach is presented for the proposed integrated system. A threat model of the measurements of the system components is discussed, which includes both the nominal performance and possible fault modes. A new protection level is presented to bound the maximum directional position error. The proposed approach was evaluated through a kinematic test in an urban area in Japan with a focus on horizontal positioning. Test results show that by integrating RTK, Doppler with IMU/speedometer, 100% positioning availability was achieved. The integrity monitoring availability was assessed and found to meet the target value where the position errors were bounded by the protection level, which was also less than an alert level, indicating the effectiveness of the proposed approach.