BIOGRAPHY PSEUDOLITE-BASED INVERTED POSITIONING AND ITS APPLICATIONS

PSEUDOLITE-BASED INVERTED POSITIONING AND ITSAPPLICATIONS

Liwen Dai, Jinling Wang, Toshiaki Tsujii, Chris RizosSchool of Geomatic EngineeringUniversity of New South WalesSydney, AustraliaBIOGRAPHY

Liwen Dai received a B.Sc. and M.Sc. in Geodesy in 1995 and 1998 respectively, from theWuhan Technical University of Surveying and Mapping (WTUSM), P.R. China, and then joinedthe School of Geomatic Engineering, The University of New South Wales (UNSW), Sydney,Australia, as a Visiting Fellow in November 1998. Since the start of 2000 he has been a full-timePh.D. student at UNSW where his current research interests are software and algorithmdevelopment for rapid static and kinematic positioning (and attitude determination) usingintegrated GPS, Glonass and pseudolite systems.

Jinling Wang holds a Ph.D. from the Curtin University, Australia. He is currently an AustralianResearch Council Postdoctoral Fellow in the School of Geomatic Engineering, UNSW. Jinlinghas authored over 100 refereed journal and conference publications, two widely-used commercialsoftware packages, and has received over 10 academic awards. He is Chairman of the WorkingGroup "Pseudolite applications in Engineering Geodesy", of the International Association ofGeodesy's (IAG) Special Commission 4, and a member of the Editorial Advisory Board of thejournal GPS Solutions.

Toshiaki Tsujii is a senior researcher of the Flight Systems Research Center, National AerospaceLaboratory (NAL), Japan, where he has been investigating aspects of satellite navigation andpositioning for ten years. In Feb. 2000 he commenced a 2 year visit within the SatelliteNavigation and Positioning (SNAP) Group, at the School of Geomatic Engineering, UNSW, as aJST postdoctoral research fellow. Toshiaki holds a Ph.D. in applied mathematics and physicsfrom Kyoto University. His current research interest is kinematic GNSS positioning of airbornevehicles.

Chris Rizos, B.Surv. (UNSW) Ph.D. (UNSW), has been an academic staff member of the Schoolof Surveying (renamed the School of Geomatic Engineering in 1994) at UNSW, since 1987,where he is now a Professor. Chris is leader of the SNAP group, a Fellow of the IAG and of theAustralian Institute of Navigation. He has published over 150 papers, as well as authored and co-authored several books relating to GPS and positioning technologies.

ABSTRACTIn this paper, the pseudolite-based inverted positioning system, where a ‘constellation’ of GPSreceivers with precisely known 'orbit' tracks a mobile pseudolite, is described. The systemconsists of an array of GPS receivers, the reference pseudolite (or reference GPS satellite) and themobile pseudolite. Two configurations of the inverted positioning system are discussed. Theimplementation challenges for the pseudolite-based inverted positioning system, includinggeometry optimization, multipath and receiver array location dependent errors have beeninvestigated. Several applications using the inverted positioning concept, including deformationmonitoring and navigation services based on pseudolite installed on stratospheric airships, arediscussed.

A static experiment was carried out using six NovAtel GPS receivers and two IntegriNauticsIN200CXL pseudolite instruments, on the UNSW campus, on the 4th April 2001. Theexperimental setup and operating procedures are described in detail. The carrier phasemeasurements have been processed in an 'inverted' mode. The results indicate that the accuracyof the inverted phase positioning is less 5mm. The static experiment has indicated that the twoconfigurations for the inverted positioning are feasible in practice.

INTRODUCTIONOver the last decade or so, GPS positioning has played an increasing role in both surveying andnavigation, and has become an indispensable tool for precise relative positioning. However, insome situations, such as in urban canyons, dam monitoring in valleys and in deep open-cutmines, the number of visible satellites may not be sufficient to reliably determine precisecoordinates. Furthermore, it is impossible to use GPS for precise indoor positioning.

Pseudolites, which are ground-based transmitters of GPS-like signals (i.e. “pseudo-satellite”), cansignificantly enhance the satellite geometry, and even replace the GPS satellite constellation insome circumstances. The pseudolites typically transmit pseudo-range and carrier phasemeasurements signals at one or both the GPS frequency bands (L1: 1575.42MHz; L2:1227.6MHz). The use of pseudolites can be traced back to the early stages of GPS developmentin the late 1970s, at the Army Yuma Proving Ground in Arizona (Harrington & Dolloff, 1976),where the pseudolites were used to validate the GPS concept before launch of the first satellites.In the mid 1980s, the RTCM committee SC-104 ('Recommended Standards for DifferentialNAVSATR GPS Service') designated the Type 8 Message for the pseudolite almanac, containingthe location, code and health information of pseudolites (Kalafus et al., 1986). With thedevelopment of the pseudolite techniques and GPS user equipment during the last decade,pseudolites can now be used to enhance the availability, reliability, integrity and accuracy inmany applications, such as aircraft landing (Holden & Morley, 1997; Hein et al., 1997),deformation monitoring applications (Dai et al., 2000; 2001a), Mars exploration (Lemaster &Rock, 1999), precision approach applications, and others (Barltrop et al., 1996; Wang et al.,2000).