A New GNSS Campaign Network for Volcano Monitoring on Saba and St. Eustatius: Design, Initial Results, and Linking to Historical Data

Saba and St. Eustatius are the northernmost islands of the Lesser Antilles Volcanic Arc and host the active but quiescent volcanoes Mt. Scenery and The Quill. KNMI operates a multi-sensor geophysical monitoring network on these islands to monitor potential volcanic unrest and regional tectonic processes. Continuous GNSS networks form a key component of volcano deformation monitoring but are typically sparsely distributed and may not capture all local signals. For this reason, continuous GNSS networks are commonly complemented by campaign GNSS measurements.

On Saba and St. Eustatius, campaign GNSS points were installed and surveyed by other research institutes between 1998 and 2009. Because many of these points were deteriorated, in 2023, KNMI implemented new campaign GNSS points on both islands. Where possible these were placed in close proximity to historical points, but we also installed points at additional locations to fill monitoring gaps. Links between old and new markers were established by means of short baseline analysis if feasible.

Rather than installing permanent marker pins that require tripod setups, we developed a campaign setup based on a female threaded metal anchor glued into the ground. GNSS antennas are mounted on a removable pole which is screwed into the anchor, providing a stable and repeatable setup. This design reduces setup time and minimizes the risk of unintended antenna movement. We present the layout of the new GNSS campaign network on both islands and show positioning results from the baseline analysis as well as the 2023-2025 campaign measurements.