This study establishes GNSS-based azimuth remeasurement scenarios for geomagnetic observatories, overcoming limitations of traditional astronomical methods. Five prioritized workflows address diverse field conditions. Validations at Hongshan, Quanzhou, and Yulin observatories confirm Scenario I (dual-GNSS alignment) and Scenario II (angular conversion) feasibility. Preliminary error analysis informs a deployment priority sequence, providing scalable solutions for complex environments.

This study evaluates the data quality and long-term robustness of reference fluxgate theodolites in Geomagnetic Network of China (GNC). Results show high stability in reference instruments and no drift. Operator dependent errors were identified as the primary contributor in observer data. The study highlights the critical role of comparisons. Future efforts should integrate sensors and automation technologies to minimize human errors, thereby providing a higher quality data for studies.

The objective of this study is to rescue and integrate historical data from eight pioneering geomagnetic observatories in China. Data quality is significantly improved through integration. The integrated dataset is now publicly available for easy access and use by the academic community and the public. These datasets are of great significance for optimizing historical geomagnetic field models, investigating changing magnetic fields, the main geomagnetic field.

The Sheshan observatory has nearly 150 years of observation history, and its observation data have important scientific value. However, with time, these precious historical data face the risk of damage and loss. We have carried out a series of rescues on the historical data of the Sheshan observatory. New historical datasets were released, including the quality-controlled absolute hourly mean values of three components (D, H, and Z) from 1933 to 2019.

The daily variation amplitude of geomagnetic component Z could represent the diurnal variation strength of geomagnetic field. The ionospheric conductivity, neutral wind in ionosphere and the complicated underground electrical structures make combined action to effect the feature of the Z daily variation amplitude in China. This paper will provide the background information or reference to researchers who study the geomagnetic diurnal variation or to analyse the anomaly.