Digital Zenith Camera of the University of Latvia

Abstract

Design of digital zenith camera in Institute of Geodesy and Geoinformatics of the University of Latvia started in 2009. Now, after tests of a prototype, improvements of design and manufacturing of the second version, it has reached operational status. The paper describes construction of camera, features of it‘s control software. Vertical deflection determination results are discussed.

Performance Analysis of Latvian Zenith Camera

“…Unlike other known instruments of this type, our zenith camera can employ any amount of rotation between observation positions; actual orientation of it is determined by astrometric processing of star field images (Zariņš et al, 2016). As 180 dg rotation offers the best definition of expected quasi-circular trajectory of ellipsoidal zenith projection on rotating instrument coordinate system, a regular observation session is made of a number of such position pairs.…”

“…Here X, Y are already corrected for residual tilt according to (1) in (Zariņš et al, 2016); ξ and η are North-South and East-West components of vertical deflection; X  and Y  represent drift speed components.…”

“…Star image CCD coordinates were fitted to respective coordinates in reference star catalog using least squares approximation by 6-parameter transformation model; CCD coordinates of astrometric zenith point for the mid-exposure time moment were calculated. Tiltmeter measurements were approximated using linear time dependency; residual tilt for the mid-exposure time moment was calculated -to be applied as correction to zenith point CCD coordinates according to formulas (1) in (Zariņš et al, 2016). Atmospheric turbulence effect on star images together with discrete nature of images (with pixel size close to 1ʺ) seem to be dominating dispersion sources for astrometric model.…”

“…Basically, design of digital zenith camera in the institute of Geodesy and Geoinformatics of the University of Latvia was concluded in 2016 (Zariņš, Rubans, & Silabriedis, 2016). Up to the end of 2017 a number of test observations at a fixed test site, as well as field observations at about 70 different sites were performed.…”

The Use of the Automated Digital Zenith Camera System in Istanbul for the Determination of Astrogeodetic Vertical Deflection

“…As effective and fully automated systems, the development of the DZCSs in Germany and Switzerland (e.g., Hirt and Bürki 2003;Bürki et al 2004;Hirt 2004;Müller et al 2005;Hirt and Seeber 2008;Hirt et al 2010a) have inspired many other researchers in geodesy, particularly astrogeodesy. Scientists in several countries have developed their own DZCSs: Poland (Kudrys 2007), latvia (Abele et al 2012;Zariņš et al 2016;Zarins et al 2018), Turkey (Halıcıoğlu et al 2012;Halıcıoğlu et al 2016), China (Wang et al 2014;Tian et al 2014) and Hungary (Hirt et al 2014). Each of these systems has unique design features, including hardware components and automation software.…”