Abstract
AbstractIn urban areas, the Global Navigation Satellite System (GNSS) can lead to position errors of tens of meters due to signal obstruction and severe multipath effects. In cases of 3D-positioning, the vertical coordinate is estimated less accurately than are the horizontal coordinates. Multisensor systems can enhance navigation performance in terms of accuracy, availability, continuity and integrity. However, the addition of multiple sensors increases the system cost, and thereby the applicability to low-cost applications is limited. By using the concept of receiver clock modelling (RCM), the position estimation can be made more robust; the use of high-sensitivity (HS) GNSS receivers can improve the system availability and continuity. This paper investigates the integration of a low-cost HS GNSS receiver with an external clock in urban conditions; subsequently, the gain in the navigation performance is evaluated. GNSS kinematic data is recorded in an urban environment with multiple geodetic-grade and HS receivers. The external clock stability information is incorporated through the process noise matrix in a Kalman filter when estimating the position, velocity and time states. Results shows that the improvement in the precision of the height component and vertical velocity with both receivers is about 70% with RCM compared with the estimates obtained without applying RCM. Pertaining accuracy, the improvement in height with RCM is found to be about 70% and 50% with geodetic and HS receivers, respectively. In terms of availability, the HS receiver delivers an 100% output compared with a geodetic receiver, which provides an output 99⋅4% of the total experiment duration.
Highlights
The Global Navigation Satellite System (GNSS) can provide position, velocity and timing (PVT) information
This paper addresses the feasibility of using a standalone HS multi-GNSS single-frequency receiver with external clock on a mobile platform in an urban environment
Measurement data recorded with receivers (JAVAD 0082 and u-blox 1771) connected with miniaturised atomic clock (MAC) SA.35 m are analysed in terms of their quality and statistics
Summary
The Global Navigation Satellite System (GNSS) can provide position, velocity and timing (PVT) information. With three coordinates and a receiver clock bias, there are four unknowns to be estimated at each epoch This leads to a weakened observation geometry and the requirement of a minimum of four satellites to obtain a solution (Bednarz and Misra, 2006). In RCM, the receiver clock is modelled with a linear polynomial over certain time spans, which allows avoidance of an epoch-wise estimation of the clock time bias It strengthens the observation geometry and the positioning results are more robust. Results from a kinematic experiment in an open-sky environment shows that the precision of the up coordinate is improved by about 50–70% when RCM is applied; the reliability of the system is amplified further, leading to a more robust position estimation (Krawinkel and Schön, 2016). Conclusions are drawn based on the performance of the HS and geodetic receivers in the urban scenario
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