Metrological Traceability for the Absolute Gravity Italian Network

The Absolute Gravity Italian Network project aims to update Italy's gravity network, currently aligned with the IGSN71, established in 1971. The project's main objective is to establish a new gravity reference using absolute gravity observations conducted according to international standards, as outlined in the "CCM-IAG Strategy for Metrology in Absolute Gravimetry. According to IAG resolution No. 2 and subsequent resolutions, there is a need to ensure metrological traceability for Absolute Gravity measurements. This can be achieved through various methods, including the establishment of reference sites, international comparisons of absolute gravimeters and calibration by comparison. Measurements have been conducted at suitable locations throughout Italy. The validated data will be stored in an open database and also included to the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt für Kartographie und Geodäsie. This will contribute to the new International Terrestrial Gravity Reference System. All the gravimeters used in these measurements have participated in international comparisons organized by CCM and/or EURAMET TC-M, yielding compatible results. To further validate these results and ensure traceability to the SI units, additional comparisons between the absolute gravimeters used in the measurements were conducted just before the measurement campaign. The primary Italian reference instrument is the absolute gravimeter IMGC-02, developed and maintained by INRiM, with an expanded measurement uncertainty of 8.5 µGal. The comparison sites, located at INRiM, feature solid basements that ensure good measurement repeatability and low floor noise, contributing to the final measurement uncertainty. The paper presents the results of these measurements.