Biograph: Prof Geng holds a Bachelor’s degree in Engineering Surveying and Space Geodesy from Wuhan University, China in 2004, and graduated with a Ph.D. degree in GPS Geodesy from Nottingham Geospatial Institute, the University of Nottingham, UK in January 2011. His PhD topic is ‘Rapid ambiguity resolution in GPS precise point positioning (PPP)’ which is among the first few dissertations systematically discussing PPP ambiguity resolution under the supervision of Prof Alan Dodson. Prof Geng afterwards worked as a primary investigator and an enterprise research fellow at University of Nottingham on the industrial application of real-time PPP in remote areas such as deserts and open oceans, which was based on a 12-month grant from EPSRC (Engineering and Physical Sciences Research Council, UK). From 2012 to 2015, he stayed in San Diego of the USA and held a Green scholar and postdoctoral position at Scripps Institution of Oceanography (SIO), University of California San Diego, USA and worked on earthquake and tsunami early warning using real-time GPS and its integration with accelerometers. The project was initially funded by the Cecil H. and M. Green Earth Science Foundation and later supported by a four-year NASA AIST (Advanced Information System Technology) program. Since October of 2015, he has been a full professor in GNSS Geodesy at Wuhan University and was elected as IAG Fellow in 2019.
Title:Towards global instantaneous decimeter-level positioning using multi-constellation and multi-frequency GNSS
Abstract: Autonomous driving has greatly promoted innovations in both GNSS hardware devices and positioning algorithm, owing to its requirement of both high precision positions and critical safe standard. We develop a method to achieve global instantaneous decimeter-level positioning by virtue of both multi-GNSS and triple-frequency observations contributing to precise point positioning (PPP). Inter-system phase biases (ISPBs) for two wide-lane observables are firstly computed for each station to form inter-GNSS resolvable ambiguities, and then correspondingly two wide-lane fractional-cycle biases (FCBs) computed for each satellite to recover the integer property of single-station ambiguities. With both ISPB and FCB products, we can accomplish tightly-coupled multi-GNSS PPP wide-lane ambiguity resolution (PPP-WAR) using only a single epoch of triple-frequency observations on a global scale. To verify this method, we used one month of GPS/BeiDou/Galileo (E1/E5a/E5b)/QZSS data from 107 globally distributed stations, and one hour of such multi-GNSS data collected on a vehicle moving in an urban area. The resultant single-epoch positions reached a mean accuracy of 0.22 m, 0.18 m and 0.63 m for the east, north and up components, respectively, in case of abundant triple-frequency observations from over 15 satellites. Most interestingly, a smaller positioning error of 0.12 m, 0.10 m and 0.42 m for the three components was achieved by Galileo-only PPP-WAR (E1/E5a/E6) with more than 9 satellites on view, showing the lower observable noises of frequency combination E1/E5a/E6 comparing with those of their multi-GNSS counterparts. Finally, we expect that the prospect of instantaneous PPP-WAR in aiding driverless vehicles can be more promising if, whenever possible, integrated with inertial sensors and/or smoothed through multi-epoch data.