Redução de sondagem para maré-GNSS: uma avaliação da método RTK-NTRIP Na Baía de Guanabara

Abstract

This study evaluates GNSS-tide–based survey reduction in Guanabara Bay, emphasizing RTK positioning via NTRIP as an alternative to conventional reductions based on tide gauges, whose spatial representativeness is limited and subject to co-tidal errors. Bathymetric and GNSS data were acquired under real operating conditions and processed with real-time differential corrections. The vertical separation (β) between the reference ellipsoid and the Reduction Level (NR) was estimated from the Ilha Fiscal station (F-41) and then adjusted in CARIS through an iterative procedure (reprocessing the GNSS-tide surface, generating the difference surface relative to the tide-gauge solution, and computing statistics) with the goal of bringing the mean of differences close to zero. GNSS-reduced depths were compared with those from the traditional method, yielding near-zero mean biases, centimeter-level dispersions. In comparative terms, we obtained an equivalent bias and a dispersion about four times smaller than the best case reported by Ramos and Krueger (2009), reinforcing the method’s maturity and the effectiveness of the applied quality control. The results indicate that GNSS tide via RTK/NTRIP is an operationally viable alternative to conventional tide-gauge reduction, enabling greater geodetic consistency and better spatial adequacy of corrections, while still requiring an initial β calibration relative to a local reference tide station.