Stereo imaging and X-band radar wave data fusion: An assessment

Abstract

The use of spatial and spatio-temporal data is rapidly changing the paradigm of wind wave observations, which have been traditionally restricted to time series from single-point measurements (e.g. from buoys, wave gauges). Active and passive 2D remote sensors mounted on platforms, ships, airplanes and satellites are now becoming standards in the oceanographic community and industry. Given the covered area ranging from centimeters to kilometers, such sensors are now a valuable tool for ocean and coastal observations. In this paper, we intercompare spatio-temporal wind wave data acquired with two state-of-the-art techniques, namely the stereo wave imaging and the X-band marine radar. The comparison was performed by operating the two instruments on an oceanographic research platform during a crossing-sea condition. We analyzed the statistical properties of the wave field, and its directional and omni-directional energy distributions. From our analysis, we suggest that stereo data can be exploited to find the best radar Modulation Transfer Function and scale factor needed to estimate wave parameters. Moreover, the fusion of the two systems will allow to broaden the scales covered by any one measurement, and to retrieve reliable directional wave spectra from short (∼1 m) to midwavelengths (∼100 m). Highlights ► We compare spatio-temporal wave data from stereo imaging and X-band radar. ► We use stereo data to improve the radar Modulation Transfer Function (MTF) and scale factor. ► The fusion of the two systems will allow covering spatial scales broader than any one measurement. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

On Evolution of Young Wind Waves in Time and Space

“…Due to improvements in computational power and computational algorithms, the application of stereo video imaging in field experiments with cameras either installed on offshore platforms or on a moving vessel expanded significantly in recent years. The comparison of video imaging results with those obtained using a standard instrumentation that was carried out in those experiments provided evidence that at open sea scales, stereo wave imaging is effective to retrieve data on medium-to-short wavelengths; see [17] and additional references therein. Stereo video imaging, similarly to alternative optical methods of reconstruction of the instantaneous water surface shape, requires considerable computational resources that currently limit their effective spatial resolution and the overall duration of continuous imaging.…”

La Jument lighthouse: a real-scale laboratory for the study of giant waves and their loading on marine structures

“…For this analysis, only wave components of frequency higher than 0.5 Hz were selected, thus removing sparse spikes close to the poorly matched areas. Following the standard procedure, the dataset was analysed by splitting the sea surface region and the time interval in adjacent and non-overlapping subrecords [37]. To this end, we have selected 14 spacetime regions V s (with s = 1, 2, .…”

Toward real-time optical estimation of ocean waves’ space-time fields

“…At a larger scale (10…300 meters wavelength), radar is a commonly used system to estimate the spectral properties of 2D wave fields (Young et al, 1985;Nieto Borge et al, 2013). Despite its popularity, this technology does not allow the direct observation of the wave field, that instead must be inferred, from the radio wave backscatter, through an empirically defined Modulation Transfer Function (MTF) (Nieto Borge et al, 2004;Benetazzo et al, 2018). At a medium scale (0.2…50 meters wavelength) optical stereo-based 3D reconstruction techniques offer an excellent tradeoff between reconstruction accuracy, resolution and cost (Jähne et al, 1994;Benetazzo et al, 2012).…”