• Senior Scientist, GeoForschungsZentrum Potsdam, since 1999
• Adjunct Professor, National Time Service Centre, CAS, since 2008
• Overseas Communication Assessor, Education Minstry of China, since 2005
• Adjunct Professor, University ChangAn, since 2004
• Adjunct Professor, Insitute of Geodesy and Geophysics, CAS, 2005 - 2008
• Overseas Assessor, Chinese Academy of Sciences, 2005 - 2008
• 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

Author and Co-authored Books:

Xu, G. (Ed) (2009, in processing):
Sciences of Geodesy
Springer Heidelberg
ca. 460 pages, in English

This hand and reference book describes sciences of different areas of geodesy, about the history, the theory, the objective, the development, the highlight of the research, the applications, the problems and the future of the individual areas. They are written by different authors specialized in the related areas as follows:

Topics -- Authors
Preface -- Guochang Xu
Aerogravimetry -- Rene Forsberg
Superconducting Gravimetry -- Jürgen Neumeyer
Terrestrial Gravimetry -- Ludger Timmen et al.
Deformation and Tectonics -- Luisa Bastos et al.
Analytic Orbit Theory -- Guochang Xu
Inversion Problem -- Jürgen Kusche et al.
Airborne Lidar -- Tianyuan Shih
InSAR - Ye Xia
Marine Geodesy - Jörg Reinking
Adjustment and Filtering -- Yuanxi Yang
GPS/Galileo Systems -- Oscar Colombo
Equivalence Principle of GPS Algorithms -- Guochang Xu et al.
Earth Rotation and Polar Motion -- Harald Schuh et al.
Laser Ranging -- Ludwig Combrinck

Keywords: Aerogravimetry, Superconducting Gravimetry, Terrestrial Gravimetry, Deformation and Tectonics, Analytic Orbit theory, Inversion Problem, Remote Sensing (Lidar), Radar Interferometry (InSar), GPS/Galileo Systems, Equivalence Principle of GPS Algorithms, Marine Geodesy, Adjustment and Filtering, Earth Rotation and Polar Motion, Laser Ranging.

Contents: Preface. - Aerogravimetry. - Superconducting Gravimetry. - Terrestrial Gravimetry. - Deformation and Tectonics. - Analytic Orbit Theory. - Inversion Problem. - Airborne Lidar. - InSAR. - Marine Geodesy. - Adjustment and Filtering. - GPS/Galileo Systems. - Equivalence Principle of GPS Algorithms. - Earth Rotation and Polar Motion. - Laser Ranging.


Xu, G. (2008):
Orbits
Springer Heidelberg
ISBN 978-3-540-78521-7, 230 pages, in English

This hand and reference book describes and derivates the solutions of the equations of satellite motion perturbed by the extraterrestrial disturbances and the geopotential disturbances. The equations of extraterrestrial disturbances are solved by means of discretization and approximated potential function as well as Gaussian equations individually and accordingly. The equations of geopotential disturbances are solved by using symbolic mathematical operation. Singularity-free theory is outlined to make the orbit theory without problem of singularity. Simplified disturbed equations of motion are proposed to simplify the solutions. Applications of the theory for the analytic orbit determination are also discussed. Other contents are supplemented to form a book which covers the complete orbit theory and the analytic solutions of the disturbed satellite orbits as well as their applications. So this is the first book since satellite era which describes systematically the orbit theory with analytic solution of the second order with respect to all of the extraterrestrial disturbances and the geopotential disturbances and meanwhile free of singularity. Based on such theory the algorithms of orbit determination can be greatly renewed and many interesting areas of applications are opened. Orbit determination may be carried out analytically and the kinematics and dynamics of the orbit may be described physically and explicitly. Real time orbit determination, which is difficult to be realised due to the adjustment and filtering as well as integrator used in numerical algorithms, is now possible. Deeper insight of the physics of disturbances becomes possible for applications.

Keywords: Satellite Orbits, Analytic Solutions, Solutions of Extraterrestrial Disturbances, Solutions of J2 and other Geopotential Disturbances, Analytic Orbit Determination, Singularity-Free Theory, Applications

Contents: Introduction.- Coordinate and Time Systems.- Keplerian Orbits.- Perturbations of the Orbits.- Solutions of C20 Disturbance.- Solutions of other Geopotential Disturbances.- Solutions of Extraterrestrial Disturbances.- Numerical Orbit Determination.- Analytic Orbit Determination.- Singularity-Free Theory and Discussions.


Xu, G. (2007):
GPS - Theory, Algorithms and Applications
Second Edition
Springer Heidelberg
ISBN 3-540-67812-3, 350 pages, in English

Extended contents:
Introduction of GPS, Galileo, GLONASS, GNSS systems
Equivalence of the uncombined and combining algorithms
The theory and algorithm of the independent parameterisation of the GPS observation models
Equivalence theorem of the GPS data processing algorithms
Applications of the GPS theory and algorithms for software development
Algebra solution of the variation equation in the orbits determination
Discussions and comments, etc.

Reduced contents:
Part of the ambiguity related contents

Keywords: GPS, Positioning and Navigation, Satellite Geodesy, Adjustment and Filtering, Ambiguity Resolution, Orbit Determination, Equivalence Theorem and Algorithms, Independent parameterisation, Software Development

Contents: Introduction.- Coordinate and Time Systems.- Satellite Orbits.- GPS Observables.- Physical Influences of GPS Surveying.- GPS Observation Equations and Equivalence Properties.- Adjustment and Filtering Methods.- Cycle Slips Detection and Ambiguity Resolution.- Parameterisation and Algorithms of GPS Data Processing.- Applications of GPS Theory and Algorithms.- Perturbed Orbit and its Determination.- Discussions.


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/Galileo software (MFGSoft). 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



Author and Co-authored GPS Software:

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. (1998):
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.