Geodetic GPS Tide Gauge

A geodetic GPS tide gauge is a tide-gauge installation whose benchmark is co-located with a continuous GNSS receiver so the gauge’s vertical land motion is measured directly. The GNSS station, tied to the ITRF reference frame, separates the geocentric (absolute) sea-level signal from local crustal motion such as subsidence or glacial isostatic adjustment, the term that otherwise corrupts a relative tide-gauge trend. This is the backbone of the GLOSS network and of altimetry calibration, where the gauge plus GNSS provides an independent geocentric reference. Without the co-located GNSS, a tide-gauge trend mixes ocean change and land movement and cannot be compared to satellite altimetry.