Abstract
We evaluated the performance of GNSS absolute antenna calibrations and its impact on accurate positioning with a new assessment method that combines inter-antenna differentials and laser tracker measurements. We thus separated the calibration method contributions from those attainable by various geometric constraints and produced corrections for the calibrations. We investigated antennas calibrated by two IGS-approved institutions and in the worst case found the calibration’s contribution to the vertical component being in excess of 1 cm on the ionosphere-free frequency combination L3. In relation to nearby objects, we gauge the 1sigma accuracies of our method to determine the antenna phase centers within pm ,0.38 mm on L1 and within pm ,0.62 mm on L3, the latter applicable to global frame determinations where atmospheric influence cannot be neglected. In addition to antenna calibration corrections, the results can be used with an equivalent tracker combination to determine the phase centers of as-installed individual receiver antennas at system critical sites to the same level without compromising the permanent installations.
Highlights
In a geodetic system where VLBI provides connection to the celestial reference frame and SLR to the center of the terrestrial frame, GNSS ground stations play a key role in the implementation on the observational level (Plag and Pearlman 2009; United Nations 2015; Altamimi et al 2016)
We present an assessment that utilizes a combination of inter-antenna differentials and high-precision geometric measurements to determine the unbiased phase center offset from the geometric antenna reference points (ARP)
GNSS antennas are an essential part of bringing a unified geodetic observation system on the observation level to fruition
Summary
In a geodetic system where VLBI provides connection to the celestial reference frame and SLR to the center of the terrestrial frame, GNSS ground stations play a key role in the implementation on the observational level (Plag and Pearlman 2009; United Nations 2015; Altamimi et al 2016). To reduce the vertical error by another order of magnitude and meet climate change monitoring requirements on the geodetic system of 1 mm accuracy (Plag and Pearlman 2009; NRC 2010), reliable determinations of the antenna phase center offsets (PCO) and variations (PCV) combined as phase center corrections (PCC) with respect to the tangible structure are instrumental These PCCs are currently rather weakly constrained by independent methods, and the lack of on-site phase center model tests in particular is a primary source of systematic errors and biases in GNSS processing (Dilssner et al 2008; Gross and Herring 2017; Johansson et al 2019). The IGS currently approves AC tables generated with two different principles—robotic vis-à-vis anechoic chamber, compared in
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