CCD to Marry GPS

Collins Fosu, Bernd Eissfeller, Günter W. Hein

Abstract:	The new microchip and sensor technology, charged couple device (CCD), has assumed a permanent position as the natural transducer for optical input to a computer. The CCD combined with the microcomputer has revolu-tionised the whole discipline of observational astronomy all stages from data gathering to data analysis, presen-tation and use. This has brought about renaissance in as-trometry. Not only has it brought the convenience of digital imaging to field astronomy but has also great po-tential in determining very accurate astronomic latitude and longitude of a point at great speed and ease, compati-ble to GPS. This has generated great interest in geodesists to combine CCD with satellite positioning systems to sense the local gravity field to determine deflection of the vertical and local or precise geoid for levelling and other applications in geodesy. The principle here is to determine astronomic co-ordinates using CCD and compare them to geodetic co-ordinates from GPS. The difference gives the deflection of the vertical in quasi real time. While the CCD has revolutionised astronomical imaging, it is important to note that there are problems associated with using CCDs. In the case of geodetic astronomy some of the main problems are the size of the CCD chip, the accuracy of measuring the image co-ordinates and the systematic er-rors that can cause changes in the spatial structure of the obtained image affecting their fidelity, the instrumental and timing errors of the camera. These problems and how to deal with them are discussed in this paper. In this work we employ least squares smoothing techniques on data from astronomic observations using CCD zenith camera and compare the resulting astronomic co-ordinates with geodetic co-ordinates from GPS to de-termine deflections of the vertical and subsequently local geoids. We present preliminary results of research work going on at IfEN. These results clearly indicate that it is possible to determine the astronomic values to an accu-racy better than the 0.3 arcsecond required for precise orthometric height determination.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	69 - 80
Cite this article:	Fosu, Collins, Eissfeller, Bernd, Hein, Günter W., "CCD to Marry GPS," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 69-80.
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