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Abstract

New Zealand’s position straddling the Australian and Pacific plate boundary means it experiences both secular plate motion, and non-secular motions associated with earthquakes. The purpose of New Zealand's 39 PositioNZ CORS sites are to maintain the national datum as these events occur. Positions and velocities from the PositioNZ network are used to develop a deformation model which translates between present day IGS20 coordinates into NZGD2000. Maintaining an up-to-date deformation model is a technical challenge in the face of ongoing earthquake deformation and New Zealand's small tax base is unable to pay for a dense network of GNSS sites that would allow for more comprehensive land movement monitoring. Our long term datum monitoring is done through a homogeneously reprocessed solution including historical data from 39 PositioNZ CORS sites, 149 Geonet CORS sites, and 157 private CORS sites (new addition) all aligned to 195 IGS20 core reference sites using a double difference strategy on Bernese 5.4 GPS software. This solution is computed with IGS Final products from 27 November 2022 to present, and re-analysed products from 2000 - 2020. This solution applies newly available models in Bernese 5.4 including for FES2016b ocean tide loading, apriori troposphere values from VM3G, and DESAI2016 sub-daily pole model and IERS2010_V1.2.0 mean pole model. The results of this solution will be presented and discussed, including the effect of switching to from IGB14 to IGS20 and an assessment of the suitability and value added by including CORS sites installed for a variety of purposes in our network solution.