Progress Update on a Global Collaboration for GNSS Receiver Antenna Calibration: Results from the IGS Ring Calibration Campaign (IGS ringCalVal)

GNSS station operators and network analysers face the challenge of achieving consistent phase center corrections (PCCs), particularly since multi-GNSS calibrations are not available for all antennas. To address this issue, a global initiative involving nine calibration organizations has launched a comprehensive ring calibration campaign. This collaboration aims to enhance the consistency of calibration methods and establish a robust quality assessment framework by sharing six structurally diverse antenna samples for calibration. The recommended methods by the International GNSS Service (IGS), including anechoic chamber and field robot calibration methods, are participating with the aim of defining a global benchmark for the accuracy and reliability of receiver antenna PCCs.

Over the past year, the campaign has made significant progress. Measures and methods to easily compare the PCC patterns and define a benchmark value for consistent PCCs have been established. In this contribution, we present the latest results of this campaign. We demonstrate in the pattern domain that the consistency among the system/frequencies per receiver antenna design varies around an uncertainty level of ±1 mm, with an elevation-dependent effect also needing consideration. In the position domain, we present system-specific PPP results per antenna and facility. For example, the variation among different antennas and facilities for classical GPS ionosphere free linear combination is generally below 2-3 mm for the horizontal component and below 5 mm for the vertical component when comparing calibration sets among the various facilities. We also present comprehensive and effective comparison methods for the pattern domain and evaluation tools for the position domain that are essential for establishing a globally fair and transparent benchmark for receiver antenna PCC calibration and verification processes.