X-Band Radar as a Tool to Determine Spectral and Single Wave Properties

Abstract

The Wave Monitoring System WaMoS II was developed for real time measurements of directional ocean waves spectra to monitor the sea state from fixed platforms in deep water or coastal areas as well as from moving vessels. The system is based on a standard marine X-Band radar used for navigation and ship traffic control. WaMoS II digitises the analogous radar signal and analyses the sea clutter information to obtain directional wave spectra from the sea surface in real time even under harsh weather conditions and during night. Spectral sea state parameters such as significant wave height, peak wave period and peak wave direction both for wind sea and swell are derived. Within the EU funded project ‘MaxWave’ and the German project ‘SinSee’ new algorithms were developed to determine sea surface elevation maps from radar images which are used to investigate the spatial and temporal evolution of single waves simultaneously. In this paper a short overview describes the calculation of surface elevation maps and the detection of individual waves. Considering two case studies, the results of spatial single wave detection and corresponding temporal single wave properties are compared and discussed. Individual wave parameters derived from radar images are compared to individual waves measured by a buoy. An application of the method to characterise extreme sea states is discussed.

Estimate of significant wave height from non-coherent marine radar images by multilayer perceptrons

“…Since standard non-coherent X-band marine radar systems allow to scan the sea surface with high temporal and spatial resolutions, they are able to monitor the sea surface in time and space [14]. The combination of the temporal and spatial wave information permits to obtain wave data, such as the wave spectrum, being related to sea state parameters [4,6,9]. The use of non-coherent marine radars allows the detection of wave field features from moving ships, as well as from on-and off-shore platforms.…”

“…These non-coherent radars image the sea surface at grazing incidence with horizontal polarization. Radar images are caused by the interaction of the electromagnetic fields transmitted by the radar antenna with the sea surface roughness and ripples due to the local wind [4,7,8]. This interaction produces a backscatter of the electromagnetic fields, which is commonly known by sailors as sea clutter, and it is an undesirable signal for navigation purposes.…”

“…Using these data sets, the spatial and temporal variability of the sea surface is analyzed to extract an estimation of the so-called wave spectrum [4,7,9]. From this wave spectrum, typical sea state parameters, such us characteristic wave periods, wavelengths and wave propagation directions, can be derived to describe each sea state [6].…”

“…H s is usually estimated using in-situ sensors, such as buoys, recording time series of wave elevation information. A complementary technique to analyze ocean waves is to use remote sensing imaging methods, such as coherent radars [1][2][3], or conventional X-band marine radars [4][5][6], which are non-coherent radars commonly installed in moving vessels, as well as in on-and off-shore platforms, or marine traffic control towers. These non-coherent radars image the sea surface at grazing incidence with horizontal polarization.…”

Nautical Radar Measurements in Europe: Applications of WaMos II as a Sensor for Sea State, Current and Bathymetry

“…Recent further developments allow WaMoS II to obtain sea surface elevation maps (Nieto-Borge et al, 2004), individual wave parameters (Reichert et al, 2005), wave groups (Dankert et al, 2003), the near surface current fields , bathymetry (Bell 2005, Hessner et al, 1999, and high-resolution ocean wind fields [Dankert et al ,2005].…”