Observing Ocean Surface Waves with GPS-Tracked Buoys
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Authors
Herbers, T.H.C.
Jessen, P.F.
Janssen, T.T.
Colbert, D.B.
MacMahan, J.H.
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Date of Issue
2012-07
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Abstract
Surface-following buoys are widely used to collect routine ocean wave measurements. While accelerometer
and tilt sensors have been used for decades to measure the wave-induced buoy displacements, alternative
global positioning system (GPS) sensor packages have been introduced recently that are generally smaller,
less expensive, and do not require calibration. In this study, the capabilities of several GPS sensors are
evaluated with field observations in wind-sea and swell conditions off the California coast. The GPS buoys
used in this study include Datawell Directional Waverider and Mini Directional Waverider buoys equipped
with a specialized GPS Doppler shift sensor, and a low-cost experimental drifter equipped with an ‘‘off the
shelf’’ GPS receiver for absolute position tracking. Various GPS position receivers were attached to the
Waverider buoys to evaluate their potential use in low-cost wave-resolving drifters. Intercomparisons between
the Datawell GPS-based buoys, the experimental GPS drifter, and a conventional Datawell buoy with
an accelerometer–tilt–compass sensor package, show good agreement in estimates of wave frequency and
direction spectra. Despite the limited (several meters) absolute accuracy of the GPS position receivers, the
horizontal wave orbital displacements are accurately resolved, even in benign (significant wave height less
than 1 m) swell conditions. Vertical sea surface displacements were not well resolved by the GPS position
receivers with built-in or small patch antennas, but accurately measured when an external precision antenna
was attached to the drifter. Overall, the field tests show excellent agreement between Datawell buoys using
GPS and motion-sensor packages, and demonstrate the feasibility of observing ocean surface waves with lowcost
GPS-tracked drifters.
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Article
Description
The article of record as published may be located at http://dx.doi.org/10.1175/JTECH-D-11-00128.1
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Oceanography
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This research is supported by the Office ofNaval Research (PhysicalOceanography Program and LittoralGeosciences andOptics Program). The captain and crew of the R/V Gordon Sproul provided excellent support in the field experiments. Helpful suggestions by the anonymous reviewers are very much appreciated.
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Citation
Journal of Atmospheric and Oceanic Technology, Volume 29, pp. 944-958