Automatic Determination of Vertical Deflections in Real-Time by Combining GPS and Digital Zenith Camera for Solving the "GPS-Height-Problem"

Christian Hirt

Abstract:	The availability of automatic astronomical observation methods like a digital zenith camera in combination with highly developed satellite methods like GPS allows a real-time determination of vertical deflections. They can be utilized for astrogeodetic geoid surveys in geodesy. Physically defined height information is obtained by using geoid information in conjunction with GPS heights. Consequently the “GPS-height-problem” can be solved. As a state-of-the-art instrument for modern astronomical position determination, a digital zenith camera developed at the Institut für Erdmessung is introduced. The data flow starting from data registration with suitable sensors, data transfer to a computer and data processing by appropriate methods up to astronomical coordinates longitude and latitude and vertical deflections is presented. Emphasis is laid on algorithms for processing digital zenith images in combination with digital star catalogues. The performance of a real-time software-package for a fully automatical calculation of the astronomical latitude and longitude is described. Practical results obtained from field tests which verify the system’s accuracy of approximately 0.2 arcseconds for vertical deflections are given. In conclusion, the paper demonstrates possible applications of the automatic determination of vertical deflections in geodesy and geophysics. Current research activities for further improvements of the digital zenith camera’s accuracy and performance are outlined.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	2540 - 2551
Cite this article:	Hirt, Christian, "Automatic Determination of Vertical Deflections in Real-Time by Combining GPS and Digital Zenith Camera for Solving the "GPS-Height-Problem"," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 2540-2551.
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