The multi scenarios applicability of GNSS differential positioning technology in the remeasurement of observatory azimuth in China

The azimuth angle of geomagnetic observatory marks is crucial for ensuring the reliability of geomagnetic observation data, and its remeasurement constitutes a core task in observatory operations. The Geomagnetic Network of China comprises 46 geomagnetic observatories, most of which have been in operation for over ten years since their establishment. Thus, completing the azimuth remeasurement at these observatories has become an important mission. By comparing the precision, efficiency, and environmental adaptability of astronomical observation methods and GNSS differential positioning techniques for azimuth measurement, it is found that GNSS differential positioning technology is more suitable for the implementation of this task than traditional astronomical methods. After systematically investigating the multi scenarios in azimuth remeasurement at geomagnetic observatories based on GNSS differential positioning technology, the measurement schemes for five remeasurement scenarios are proposed, which can be applied to measurements under practical conditions such as unobstructed paths, restricted pathways, and single point deployments. Through field validations at the Hongshan, Quanzhou,and Yulin observatories, the feasibility of Scenario I (flat and clear line of sight) and Scenario II (alternative clear path available) is confirmed. Furthermore, a preliminary analysis was conducted on potential error sources in different scenarios, and a prioritized implementation sequence was established for stations that simultaneously meet the conditions of each retest scenario. This work provides a scalable technical solution for azimuth measurement in complex geomagnetic observatories environments.