Senior Scientist, GeoForschungsZentrum Potsdam, since 1999

Adjunct Professor, University ChangAn, since 2004

Overseas Assessor, Chinese Academy of Sciences, since 2004

Senior Scientist, National Survey and Cadastre - Denmark, 1998 - 1999

Scientist, GeoForschungsZentrum Potsdam, 1993 - 1998

Research Associate, Technical University Berlin, 1986 - 1993

Engineer, Institute of Geodesy and Geophysics in Wuhan, 1984 - 1986

Doktor-Ingenieur, 1992, in Geodesy, Technical University Berlin

Master of Science, 1984, in Geodesy, Chinese Academy of Sciences

Bachelor of Science, 1982, in Mathematics, Wuhan University

link to Springer

Comments are welcome!

Xu, G. (2003):
GPS - Theory, Algorithms and Applications
Springer Heidelberg
ISBN 3-540-67812-3, 315 pages, in English

This hand and reference book describes static, kinematic and dynamic Global Positioning System (GPS) theory, algorithms and applications. It is primarily based on source-code descriptions of the KSGSoft program developed by the author at the GFZ in Potsdam. The theory and algorithms are revised and extended for a new development of a multiple functional GPS software. New concepts such as the unified GPS data processing method, ambiguity-ionospheric equations and diagonarisation algorithm as well as general ambiguity search criteria, are reported for the first time. Mathematically rigorous, the book begins with the basics of coordinate and time systems and satellite orbits, as well as GPS observables, and deals with topics such as physical influences of GPS, GPS observation equations, adjustment and filtering methods, cycle slip detection and ambiguity resolution, GPS data processing, kinematic positioning and flight state monitoring, determination of perturbed orbits, and discussions.

Keywords: GPS, Positioning and Navigation, Satellite Geodesy, Adjustment and Filtering, Ambiguity Resolution, Orbit Determination

Contents: Introduction.- Coordinate and Time Systems.- Satellite Orbits.- GPS Observables.- Physical Influences of GPS Surveying.- GPS Observation Equations.- Adjustment and Filtering Methods.- Cycle Slips Detection and Ambiguity Resolution.- Kinematic and Static GPS Data Processing.- Concept of Precise Kinematic Positioning and Flight-State Monitoring.- Perturbed Orbit and its Determination.- Discussions.

Li, H.; Xu, G.; Han, H.; Zhao, H.; Chen, J.; Wang, G. (1999):
GPS and its Software Design
Science Press Peking
ISBN 7-03-007204-9/TP.1049, 337 pages, in Chinese and in C

Wang, G.; Wang, H.; Xu, G. (1995):
The Principle of the Satellite Altimetry
Science Press Peking
ISBN 7-03-004499-1/P.797, 390 pages, in Chinese

Xu, G. (1992):
Spectral Analysis and Geopotential Determination
(Spektralanalyse und Erdschwerefeldbestimmung)
Dissertation, DGK, Reihe C, Heft Nr. 397
Press of the Bavarian Academy of Sciences
ISBN 3 7696 9442 2, 100 pages, in English and German

Wang, G.; Chen, Z.; Chen, W.; Xu, G. (1988):
The Principle of GPS Precise Positioning System
Surveying Press Peking
ISBN 7-5030-0141-0/P.58, 345 pages, in Chinese

And many other publications

Xu, G. (2004):
MFGsoft, Multi Functional GPS/(Galileo) Software
with real time and post processing abilities, for local, regional and global networks static/kinematic, dynamic, kinematic/dynamic, on-board GPS applications, developed in GFZ, in C (and Fortran), an integrated GPS software, a simulator of the Galileo navigation system, and a basis of a combined software for GPS and Galileo applications, equivalent principle used to unify the un-differenced and differencing methods, diagonalisation algorithm used for keeping the sequential problem as small as possible, an independent parameterisation method used to keep the adjustment and filtering problem regular, data conditions used to guarantee the equivalence property, optimal baseline network and extended double differencing forming, fixed network or fixed orbits possible, switches of clock biases solution, data combinations, tropospheric models, IGS or broadcast orbits, reference stations, two kinds of a priori information, single point positioning and velocity determination included, ability to read or create the Sun, Moon and planets orbits, optimal ambiguity search criterion, Earth tide, ocean loading tide, mass centre correction, broadcast ionospheric model, relativity model, solar radiation and air drag models available, all possible orbit disturbance force models and orbit integration tools available, new adjustment models of solar radiation and atmospheric drag, differential solution of varaiation equations, orbit correction for regional network, dynamic or kinematic/dynamic orbit determination selectable, adjustment and filtering subroutine package, statistic and spectral analysis tools, utilities routines, very detailed theoretical descriptions and references.

Xu, G. (1999):
KGSoft, Kinematic GPS Software
a redeveloped and modified version of KSGSoft at the National Survey and Cadastre (KMS) - Denmark, designed for kinematic positioning and flight state monitoring of an airborne remote sensing system, in C, can be used in real time module, height information of starting point can be introduced, ocean loading tide model is available, kinematic troposphere model for the airplane on the air can be determined and used, ionosphere residuals modulation is available, satellite antenna centre correction is possible, ambiguity search can be carried out meanwhile in both coordinate and ambiguity domains, used for precise applications, served as a basis of education of PhD and MSc students and a tool of their studies.

Xu, G., Reigber, Ch., Schwintzer, P. (1994):
KSGSoft, Kinematic/Static GPS Software
developed at the GeoForschungsZentrum (GFZ) Potsdam, licensed and implemented in several international research institutes, in C, runs on workstation and PC, least squares adjustment, block-wise least squares algorithm, conditional and sequential adjustment and Kalman filtering are used, works on data processing of multiple kinematic/static stations simultaneously, static results can be used as conditions for kinematic solution using multiple static references, constraints of known distances between antennas of the moving platform can be introduced for precise moving state monitoring and for modifying ambiguity resolution, provides carrier phase independent velocity solution derived from instantaneous Doppler observations, velocity information are included in Kalman filtering, pre-processing integrated in main procedure, allows an increasing number of unknowns with time, debug functions integrated, switches are given to every correction models and processing modules, very effective ambiguity search algorithm through introducing conditions after the adjustment, post-processing of kinematic positioning and flight state monitoring selectable, well documented, used for aerogravimetry, aerophotogrammetry, airborne altimetry, ship-borne oceanography, car-borne surveying and volcano monitoring as well as extensive static applications.