Mapping Sea Surface Height Using New Concepts of Kinematic GNSS Instruments

Abstract

For over 25 years, satellite altimetry observations have provided invaluable information about sea-level variations, from Global Mean Sea-Level to regional meso-scale variability. However, this information remains difficult to extract in coastal areas, where the proximity to land and complex dynamics create complications that are not sufficiently accounted for in current models. Detailed knowledge of local hydrodynamics, as well as reliable sea-surface height measurements, is required to improve and validate altimetry measurements. New kinematic systems based on Global Navigation Satellite Systems (GNSS) have been developed to map the sea surface height in motion. We demonstrate the capacity of two of these systems, designed to measure the height at a centimetric level: (1) A GNSS floating carpet towed by boat (named CalNaGeo); and (2) a combination of GNSS antenna and acoustic altimeter (named Cyclopée) mounted on an unmanned surface vehicle (USV). We show that, at a fixed point, these instruments provide comparable accuracy to the best available tide gauge systems. When moving at up to 7 knots, the instrument velocity does not affect the sea surface height accuracy, and the two instruments agree at a cm-level.

Near-Coast Tide Model Validation Using GNSS Unmanned Surface Vehicle (USV), a Case Study in the Pertuis Charentais (France)

“…During our experiment in July 2020, the Cyclopée system was composed of a GNSS Trimble BD940 receiver with a Harxon D-Helix Antenna for absolute positioning, and a SENIX Toughsonic 14 acoustic altimeter for air-draft measurements, both installed on a gyro-stabilization arm (Figure 2). Chupin et al [13] have shown that, despite absolute bias than can arise from GNSS processing and terrestrial geodesy measurements, the Cyclopée system provides SSH measurements consistent with tide gauge observations at the centimetre level. At a fixed point, its performance is comparable to the classical GNSS buoy system widely used for satellite altimetry calibration.…”

“…In this study, we use the USV PAMELi (Plateforme Autonome Multicapteurs pour l'Exploration du Littoral) [13,26], which allows us to extend sea-level observations offshore and even to follow altimetry tracks. Conducted at La Rochelle University, the PAMELi project aims to develop an autonomous multi-sensor platform to better monitor and understand the evolution of the coastal area [13,26]. This coastal marine drone is based on a C-CAT3 Catamaran built by L3Harris ASV, remotely controlled through Wi-Fi, GSM, or VHF communication up to several km.…”

“…This coastal marine drone is based on a C-CAT3 Catamaran built by L3Harris ASV, remotely controlled through Wi-Fi, GSM, or VHF communication up to several km. For a complete technical review of this system, the reader is referred to the paper of Chupin et al [13].…”

“…They were originally designed to determine the precise marine geoid and thus link measurements of satellite altimeters to a coastal tide gauge [10][11][12]. Recently, Chupin et al [13] have demonstrated the ability of the Cyclopée system (a combination of a GNSS antenna and an acoustic altimeter) by mounting an Unmanned Surface Vehicle (USV) to map SSH while in motion. At a fixed point, this system provides similar accuracy than the best tide gauge systems and is therefore a way to expend accurate in-situ observations toward satellite ground tracks.…”

Geodetic Seafloor Positioning Using an Unmanned Surface Vehicle—Contribution of Direction-of-Arrival Observations

“…An innovative aspect of this experiment was to mount the GNSS/A positioning system on an Unmanned Surface Vehicle (USV) named PAMELi (Plateforme Autonome Multicapteurs pour l'Exploration du Littoral-Autonomous Multisensor Platform for Coastal Exploration). The PAMELi project was developed by La Rochelle University for repeated and multidisciplinary monitoring of shallow coastal areas (Chupin et al, 2020). The vehicle, built by ASV, is a small battery-powered catamaran (3 m-long, 1.6 m-wide, weighting 300 kg), remotely controlled from a mother-ship or land through Wi-Fi, GSM, or VHF communications.…”