Digital astro-geodetic camera system for the measurement of the deflections of the vertical: tests and results

This study introduces the new results of a novel low-cost digital zenith camera system operated in Turkey that uses astronomical and geodetic instrumentation. Currently, it is possible to determine deflections of the vertical (DoV) components by using a vast amount of information gathered from geo-referenced star images, tilt measurements, and Global Navigation Satellite System technology. This new design of an astro-geodetic camera system is used for calculating DoV components with 12 independent solutions on a test station in Istanbul, and additional observations were performed to investigate the external accuracy of the system on a test network. A specific leveling method is developed to align system toward the zenithal direction. The final results of the observations on a test station located in Istanbul indicate that the accuracy of the system is about +/- 0.19 arc-seconds in latitude and +/- 0.28 arc-seconds in longitude determination. The system has been further tested on a network with 4 control points that have averagely 20km baselines. At the test network, the root mean square of the average value of the vertical deflections is calculated as +/- 0.36 arc-seconds. Furthermore, DoV components are compared with the values that are calculated using global geopotential models.