Hans Werner Schenke

The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0

The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arc ...

Hydrosweep: New era in high precision bathymetric surveying in deep and shallow water

Abstract HYDROSWEEP, a new wide‐angle, fanshaped sonar system with 59 preformed beams, was developed in the 1980s in the Federal Republic of Germany and installed on the new German research vessel Meteor. Deep‐sea tests and especially comparisons with SEABEAM measurements were performed during the Meteor cruises M 4/1 in 1986 and M 6/4 in 1987/88. This article deals with investigations and tests in the Gulf of Biscay and in the Romanche Fracture Zone. In 1984 calibration measurements were carried out with SEABEAM on the German ice‐breaking research vessel Polarstern in the deepest part of the Romanche Fracture Zone. For comparison the identical profiles were remeasured with the new HYDROSWEEP. GPS/NAVSTAR and the Integrated Navigation System INS were used for positioning on the Meteor.

Seabottom characterization using multibeam echosounder angular backscatter: an application of the composite roughness theory

Composite roughness theory is used to characterize Southern Ocean bottom backscatter (multibeam) data. Spectral parameters based on Helmholtz-Kirchhoffs theory, D. R. Jackson et al. (1986), are determined from measured near-normal incidence values. A splicing technique using Rayleigh-Rice theory, E.Y. Kuo (1964), is employed beyond 20/spl deg/ incidence angles. Estimated roughness parameters for six deep ocean areas correlate with geology.

Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.

Gravity determination in ice covered regions by altimetry

Gravity field determination in ice covered regions of the polar marine areas is possible by using remote sensing techniques, such as satellite altimetry. An approach using standard altimetry products (ocean products, OPR) was developed and successfully applied in the Weddell Sea region, Antarctica. Comparisons to marine gravity data clearly demonstrate good agreement between both data sets.

Nordvestfjord: a major East Greenland fjord system

Fjords are deep valleys that have been flooded by encroaching seawater after ice retreat (Syvitski et al. 1987). They are produced mainly by glacial erosion, with the ice sometimes exploiting pre-existing river systems or structural weaknesses. Fjords are found in mountainous terrain in all areas affected by large glaciers and ice sheets, both today and during full-glacial periods. They are therefore a distinctive landform indicative of past glacial activity. Nordvestfjord is a 140 km long fjord that is typically about 5 km wide with very steep walls (Fig. 1a–g). The mountains surrounding Nordvestfjord rise to over 2000 m. Several small branches join the fjord before it enters the much wider and shallower Hall Bredning, part of the Scoresby Sund fjord system in East Greenland (Fig. 1b) (Dowdeswell et al. 1994 a ). The distance from the head of the fjord to the outer coast of Greenland is about 300 km (Fig. 1b), making Scoresby Sund the largest fjord system in the world at 13 700 km2. The whole fjord system was occupied by ice during the Last Glacial Maximum (Dowdeswell et al. 1994 a ). Deglaciation of Scoresby Sund began about 16 …

Antarctic Coastline Detection using Snakes

1 Extended version of a paper published in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXVIII, Part 4, 2010, 7 p. (on CD-ROM). the update cycle of the coastline data is limited by the revisit time of the imaging sensor, and the accuracy of the coastline is influenced by the ground sample distance of the images. The availability of space borne imagery has increased in recent decades due to a larger number of related satellites, including Radarsat-1, Landsat ETM+ or MODIS on board Aqua/Terra.

Applied marine geodetic research in polar regions

At the Alfred Wegener Institute for Polar and Marine Research, several geodetic methods are used to map the seafloor in polar regions. Multibeam bathymetric surveys are regularly conducted in polar regions by the institutes icebreaker Polarstern. These multibeam data are combined with bathymetric data from other sources to create bathymetric maps. The Hydrosweep multibeam system on the Polarstern is presently being modified to have a wider survey swath and the ability to collect sidescan and backscatter data. These modifications will enable researchers to survey the seafloor more efficiently and will provide important information about the seafloor materials. Satellite altimetry data is also used to supply the correlation between the earths geopotential field and the seafloor topography. This correlation can be used to guide bathymetric contouring in areas with little or no bathymetric data. Current efforts involve the study of ERS‐1 altimetry data from the Weddell Sea, Antarctica, where the altimetry d...

Seabottom roughness study using a hydrosweep–multibeam system

Seabottom profiling using a multibeam echosounder is a well‐known method to acquire a high‐resolution and high‐density data set for bathymetric mapping of survey area. The use of multibeam echosounder backscatter signals for bottom roughness characterization is a modern technique. Here, the model results of seabottom backscatter data using a hydrosweep‐multibeam system, from some of the geologically well‐known areas of Southern Oceans, are presented. Using the capabilities of multibeam systems, angular backscatter strengths are determined employing various corrections. Different bottom backscattering modeling techniques like the composite roughness [Jackson et al., J. Acoust. Soc. Am. 79, 1410–1422 (1986)] and two‐layer Helmholtz–Kirchhoff model [Talukdar et al., J. Acoust. Soc. Am. 97, 1545–1558 (1995)] for estimation of bottom roughness is applied. Various seabottom parameters like root‐mean‐square (rms) relief height, correlation lengths, attenuation coefficients, and layer thickness using the two‐laye...

Arc arrays: studies of high resolution techniques for multibeam bathymetric applications

Abstract In this paper a theoretical study is initiated to observe the utility of directional spectral estimation techniques for ‘arc array’ geometries. We examine the suitability of a 15 ° arc transducer geometry for multibeam bathymetric applications. This geometry is tested using the Bartlett method for varying arc and linear arrays of 30-elements. We also examine ‘high resolution techniques’ such as the Maximum Likelihood (ML) method and the Maximum Entropy (ME) methods (different orders), for 16-element arrays of 15 ° arc. The superiority of the high resolution methods is seen by examining the beam patterns of the 15 ° arc array under multiple source/interference conditions, i.e. the situation for rough terrain or artefactcreating conditions. Furthermore, the 15 ° arc array geometry is found to be useful for multifrequency applications at different operating wavelengths, which is useful for underwater bathymetric applications.