Development of a Digital Zenith Camera for Precision Determination of Gravitational Deflection of the Vertical
Abstract
Applied Research Laboratories, The University of Texas at Austin (ARL:UT) has developed a digital zenith camera system for the purpose of measuring the gravitational deflection of the vertical (DoV). This portable instrument is capable of determining the DoV at a location to 0.1 arc-second accuracy in approximately one hour of automated observations. The zenith camera's principles of operation and fundamental design are informed through earlier groundbreaking work by European teams. Technical advancements embodied in the ARL:UT zenith camera design include engineering innovations to attenuate systematic biases and the integration of free and open source software from the astrometry.net project, which facilitates robust and accurate astronomical positioning in real time.
The gravitational DoV is the difference between a location's geodetic coordinates, e.g., as determined via GNSS observations, and astronomical coordinates, as determined via astronomical observations relative to the local level plane. A digital zenith camera estimates astronomical coordinates by capturing star images directly overhead, solving the celestial pointing vector of the images' centers, and applying tilt corrections to account for imperfect leveling of the instrument. Additional transformations account for Earth orientation and time to convert from the celestial to terrestrial reference frames. The National Geospatial-Intelligence Agency (NGA), which has funded ARL:UT's development of the digital zenith camera, maintains geodetically stable test monuments which have been employed for testing and calibration of astronomical positioning instrumentation for many years. Testing of the ARL:UT zenith camera on these well-characterized test locations demonstrates accuracy and precision to 0.1 arc-seconds. Future test plans include locations better suited to inter-comparisons with international collaborators.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.G33B0679H
- Keywords:
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- 1217 Time variable gravity;
- GEODESY AND GRAVITY;
- 1219 Gravity anomalies and Earth structure;
- GEODESY AND GRAVITY;
- 1244 Standards and absolute measurements;
- GEODESY AND GRAVITY;
- 1294 Instruments and techniques;
- GEODESY AND GRAVITY