Low-Cost Real-Time Precise Point Positioning (PPP) Correction Service with High Availability and Accuracy
Date
2020-04-24
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Abstract
Thanks to the availability of real-time state-space correction services, real-time Precise Point Positioning (PPP) is drawing increasing interests from various applications. However, the current real-time PPP correction services are mainly designed to support professional users using high-end GNSS systems. To support many emerging applications such as precise positioning with smartphones and self-driving cars which demand high availability and accuracy as well as high cost-effectiveness, such correction services must be improved. A low-cost real-time PPP correction service has been proposed which is based on an Improved Legacy Navigation message (ILNAV) to represent and disseminate real-time precise satellite orbit, clock, and code bias with improved availability and scalability. The ILNAV can provide real-time precise satellite orbit and clock corrections for up to two hours when correction outages occur. The update rates of the ILNAV are fully scalable to accommodate various requirements in terms of communication bandwidth and accuracy. The precise satellite Differential Code Bias (DCB) is estimated with Low-Earth Orbit (LEO) satellite onboard GPS observations, which is integrated into the ILNAV as Timing Group Delay (TGD) parameter to reduce the communication load of standalone code bias messages. Since the ILNAV provides fully consistent representation and user algorithms as the standard LNAV, it can also support convenient transitions from standard LNAV to ILNAV for improved positioning performance. To support low-cost GNSS users for further improved positioning accuracy and accelerated filter convergence, highly available and precise atmospheric corrections are estimated using real-time uncombined PPP and ILNAV. The Spherical Harmonic Function (SHF) model is used to represent global ionospheric Vertical Total Electron Content (VTEC) corrections, while the Slant Total Electron Content (STEC) map and polynomial model are developed for representing regional slant ionospheric and zenith wet tropospheric corrections, respectively. The low-cost real-time PPP correction service is evaluated with an application to Android Nexus 9 tablet and u-blox devices. The results demonstrate that submeter-level horizontal positioning accuracy can be achieved with the Android Nexus 9 tablet under favorable environments, while accuracy improvement to decimeter-level can be obtained using u-blox M8T/F9P receivers with a patch antenna.
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Keywords
SSR, real-time PPP, ILNAV, DCB, global ionospheric corrections, regional atmospheric corrections
Citation
Zhou, P. (2020). Low-Cost Real-Time Precise Point Positioning (PPP) Correction Service with High Availability and Accuracy (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.