Bathymetric diffraction of basin-scale hydroacoustic signals

The ocean is nearly transparent to low frequency sound permitting the observation of distant events such as earthquakes or explosions at fully basin scales. For very low frequency the ocean acts as a shallow-water waveguide and lateral variability in bathymetry can lead to out-of-plane effects. In this paper, data from the International...

Echo reverberation and echo-to-reverberation ratio for a short pulse in a range-dependent pekeris waveguide

Synthetic aperture bathymetry estimation with a multielement array

Bathymetric estimation from multiple synthetic aperture sonar (SAS) images is challenging for shallow water environments with low frequencies. This is due to the multipath echoes corrupting the desired direct-path echoes. In an attempt to suppress some of these multipaths, the MUD synthetic aperture sonar developed at TNO has a sixteen element...

Reassessing the biostratigraphy and the paleobathymetry of the gonfolite lombarda group in the como area (Northern Italy)

Calcareous nannofossil and foraminiferal analyses have been carried out on outcrops from the type-area of the Gonfolite Lombarda Group (Como, northern Italy). In these marine fine- to coarse-grained elastics, rapidly accumulating at the southern front of the uprising Alpine range during the Oligo-Miocene, a scarce, but reliable, sequence of...

Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared

The superimposition of rhythmic bed forms of different spatial scales is a common and natural phenomenon on sandy seabeds. The dynamics of such seabeds may interfere with different offshore activities and are therefore of interest to both scientists and offshore developers. State-of-the-art echo sounding accuracy allows for the analysis of bed...

Ship detection with Envisat's alternating polarization mode

A ship detection algorithm is developed that uses Envisat ASAR imagery in alternating polarisation mode. From airborne data it is shown that of the two co-polarisations, HH is preferred over VV because of a larger ship-to-clutter ratio. Combining the HH and HV images of alternating polarisation mode, it is found that the correlation between the...

Assessment of the coastal maritime environment with airborne mid-wave infrared imagery

Images acquired with an airborne mid-wave infrared camera over the Netherlands North Sea coast are presented. A number of features are tentatively attributed to a non-thermal origin, and identified as sea bottom topography, current fronts, and tidal channels. Parallels with radar imaging are drawn

Observations of Bathymetry-Induced Ocean Roughness Modulation in In-situ Surface Slope Measurements and Coincident Airborne SAR Images

Empirical results from a field experiment in the southern North Sea have demonstrated the possibility to detect bathymetry-induced sea surface roughness modulation in the coastal zone using high frequency in-situ slope measurements provided by the Towed Laser Slopemeter. A strong correlation between enhanced/reduced slope power for ocean...

Quantitative assessment of surf-produced sea spray aerosol

The first results are presented from a quantitative model describing the aerosol production in the surf zone. A comparison is made with aerosol produced in the surf zone as measured during EOPACE experiments in La Jolla and Monterey. The surf aerosol production was derived from aerosol concentration gradients measured downwind from the surf zone...

Speckle reduction in low-contrast areas by dedicated SAR processing

The standard ERS SAR PRI product has 25 meter resolution and 3 looks. For some applications, the noise level of this product is too high; this is notably the case for the low contrasts associated with sea bottom topography. By processing RAW data using special weighting functions, an image can be produced with the same spatial resolution but a...

The use of radar for bathymetry in shallow seas

The bottom topography in shallow seas can be observed by air- and space borne radar. The paper reviews the radar imaging mechanism, and discusses the possibilities and limitations for practical use of radar in bathymetric applications, including the types of radar instruments available for this purpose.

De onderwater-acoustiek en haar toepassingen