The Digital Zenith Camera - A New High-Precision and Economic Astrogeodetic Observation System for Real-Time Measurement of Deflections of the Vertical
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During the last few years, new developments in the field of geodetic astronomy have been sparsely published. This might be due to the fact that the determination of deflections of the vertical still required relatively large efforts, both in time and in manpower, thus keeping the costs per point at a high level. Recently, the development of new high performance image sensors (CCD) at a reasonable price level enabled and initiated fundamental improvements in astrogeodetic observation instrumentations in terms of efficiency, automation, accuracy, and real-time capability. This promising development leads to a revitalization of astrogeodetic methods and offers very encouraging prospects for local high-precision astrogeodetic gravity field and geoid determinations.In this paper, two slightly different versions of the digital zenith camera, initially developed at the Institutfur Erdmessung, University of Hannover, are presented as high-precision state-of-the-art instruments. Using modern CCD technology for imaging stars and a GPS receiver, these systems allow the direct determination of the direction of the plumb line and thus its deflection from the ellipsoidal normal within a fully automated procedure in real-time. In addition to a description of the system’s design and performance, the processing steps are presented: image data acquisition, data transfer and processing giving deflections of the vertical immediately after measurement.
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Astronomical-topographic levelling using high-precision astrogeodetic vertical deflections and digital terrain model dataHirt, Christian; Flury, J. (2009)At the beginning of the twenty-first century, a technological change took place in geodetic astronomy by the development of Digital Zenith Camera Systems (DZCS). Such instruments provide vertical deflection data at an ...
Assessment of EGM2008 in Europe using accurate astrogeodetic vertical deflections and omission error estimates from SRTM/DTM2006.0 residual terrain model dataHirt, Christian; Marti, Urs; Burki, Beat; Featherstone, Will (2010)We assess the new EGM2008 Earth gravitational model using a set of 1056 astrogeodetic vertical deflections over parts of continental Europe. Our astrogeodetic vertical deflection data set originates from zenith camera ...
Hirt, Christian; Denker, H.; Flury, J.; Lindau, A.; Seeber, G. (2009)In regions with a rough topography, e.g. the European Alps, the accuracy of geoid or quasigeoid models is often reduced. For the validation and accuracy assessment of gravimetric models, astronomical levelling is a ...