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  • 1
    Publication Date: 2021-02-08
    Description: Highlights • Improved position accuracy of up to 0.08 cm using SAPOS®-corrected DGNSS • High-resolution snippet backscatter to detect and monitor UXO and its environment • Combined evaluation of bathymetry, backscatter intensities, and sediments Abstract The present study reports the evaluation of snippet backscatter information gathered with a high-frequency multibeam echosounder system (200–400 kHz) due to their usability to detect ammunition of different sizes in shallow coastal waters. Besides the feasibility of the snippet backscatter data, it was focused on the attainable horizontal accuracy in comparison to side-scan sonar and autonomous underwater vehicle (AUV) surveys. The data was collected in shallow coastal waters of up to 18 m water depth (Baltic Sea) close to an ammunition dumping site characterized by an almost flat seafloor covered with sand and silt sediments. The analysis of the multibeam compared to sidescan data indicates the snippet backscatter to be a promising prospective method for ammunition detection and being able to improve horizontal position accuracy of up to 0.08 m.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 2
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    Taylor & Francis
    In:  International Journal of Remote Sensing, 32 (16). pp. 4527-4543.
    Publication Date: 2017-07-18
    Description: In this article, wave refraction and shoaling in coastal areas were investigated and used to derive the bathymetry. With its high spatial resolution, which can achieve up to 1 m in SpotLight mode, and its low cut-off wavelength, the TerraSAR-X satellite provides images that are particularly suitable for the observation of wave behaviour in transient and shallow waters. By computing the two-dimensional (2D) spectra, shoaling waves were tracked from the open sea to the shoreline. The observed wave refraction and shoaling were compared with wave refraction laws and first-order wave theory (Airy theory). The retrieved bathymetry was compared against depth data from other sources such as ETOPO1, the US Coastal Relief Model and sea charts from the British Admiralty. A further aim of this article was the investigation of breaking waves showing up as near-shore image patterns. A theory is presented of how to derive the height of breaking waves by use of this pattern. Synthetic aperture radar (SAR) images with azimuth as well as range travelling waves were investigated. As test sites, we chose the entrance of Port Phillip near Melbourne (Australia) and the Duck Research Pier in North Carolina (USA).
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2019-09-23
    Description: This study reports an adaptation of a parametric echosounder system using 15 kHz as secondary frequency to investigate the angular response of sub-bottom backscatter strength of layered mud, providing a new method for enhanced acoustic detection of buried targets. Adaptions to achieve both vertical (0°) and non-vertical inclination (1– 15°, 30°, 45° and 60°) comprise mechanical tilting of the acoustic transducer and electronic beam steering. Data were acquired at 18 m water depth at a study site characterized by a flat, muddy seafloor where a 0.1 m diameter power cable lies 1–2 m below the seafloor. Surveying the cable with vertical incidence revealed that the buried cable can hardly be discriminated against the backscatter strength of the layered mud. However, the backscatter strength of layered mud decreases strongly at 〉3±0.5° incidence and the layered mud echo pattern vanishes beyond 5°. As a consequence, the backscatter pattern of the buried cable is very pronounced in acoustic images gathered at 15°, 30°, 45° and 60° incidence. The size of the cable echo pattern increases linearly with incidence. These effects are attributed to reflection loss from layered mud at larger incidence and to the scattering of the 0.1 m diameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to 2.6-fold increase of the signal-to-noise ratio at 40° incidence compared to the vertical incidence case.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2021-01-28
    Description: The cruise AL527 took place in the Western Baltic Sea in the period 6. – 14.09.2019. The cruise was carried out as a marine geophysical field course of Kiel University, supported by BONUS ECOMAP project. Starting and ending point of the cruise was Kiel. One stopover in Kiel took place during the cruise due to an exchange of parts of the scientific party (10.09.2019). The main aim of the cruise was to introduce marine geophysical acquisition to the students including hands-on experience in collecting marine geophysical data. This approach also included a first processing and interpretation of the data as well as the presentation of the first results. Two areas in the Western Baltic Sea were the main working areas of AL527. The first survey area was at Boknis Eck, a part of the Eckernförde Bay. The main objective in this area was to search for an underwater observatory from the Coastal Observing System for Northern and Arctic Seas Project (COSYNA), which was operated by GEOMAR and disappeared end of August 2019. For this purpose, a survey with a bathymetric multibeam system from the ”Marine Geophysics and Hydroacoustics” working group (Kiel University) was carried out. Furthermore, an underwater camera system was used for visual inspections. The second survey area was in the Mecklenburger Bay. The main objective was a pre-investigation of a buried beach for an upcoming cruise within the EU-funded project ACT-SENSE. Therefore, 2D reflections seismic, sediment echo sounder, and multibeam data were acquired. Additionally, 7 gravity cores were taken for ground trothing and sampling of the buried beach. In order to analyze major tectonic structures in the Fehmarn Belt and the Mecklenburger Bay, 12 additional seismic profiles were collected when transiting between the survey areas. Our investigations showed that a buried beach is located in the Mecklenburger Bay beneath a layer of mud. The sand deposits have an estimated variable thickness between 1m and 9m in the survey area. The top of the beach was successfully sampled with several gravity cores. Further investigations of these cores, together with the geophysical data, will be take place in the frame of the ACT-SENSE project. In the acquired bathymetric dataset from Boknis Eck some conspicuous zones could be identified, where possibly remaining parts of the missing underwater observatory are located. Unfortunately, it was not possible to validate these zones by the used underwater camera. These zones should be investigated by divers in the near future, for a reliable validation.
    Type: Report , NonPeerReviewed
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  • 5
    Publication Date: 2021-01-28
    Description: The cruise AL542 took place in the Western Baltic Sea in the period 14. – 21.08.2020. The cruise was carried out as a marine geophysical field course of Kiel University. Starting and ending point of the cruise was Kiel. One stopover in Kiel took place during the cruise due to an exchange of parts of the scientific party (18.08.2020). The main aim of the cruise was to introduce marine geophysical acquisition to the students including hands-on experience in collecting marine geophysical data. This approach also included a first processing and interpretation of the data as well as the presentation of the first results. The main survey area of the first leg of the cruise AL 542 was the Bay of Mecklenburg. In the eastern part of the bay seismic and acoustic data were collected with the aim to identify historical coastlines and buried glacial structures. Further, the central part of the bay was mapped with the multibeam echosounder to find the Blinkerhügel, a small mound with reported accumulation of manganese nodules, investigated in 2002 by Hlawatsch et al. The Blinkerhügel was clearly identified as an outcropping ground moraine. Seafloor samples at eight locations were collected with a grab from the area of the Blinkerhügel. At one location stones with manganese crusts were successfully retrieved. The four survey areas of the second leg of the cruise were Mittelgrund, Noer and Damp which are located in the Eckernförde Bay and an area near Fehmarn which is located in the northwest of the island in the Fehmarn Sund. In the region Mittelgrund in the Eckernförde Bay a wellknown, developing pockmark field was surveyed with hydroacoustic and seismic methods. Furthermore, a known pockmark near Noer was surveyed with hydroacoustic methods. From the third survey area Damp Laminaria agitate algae have been reported. The aim in this area was to check, if it is possible to detect the algae with the hydroacoustic systems. Additionally, some video transects and seafloor samples were gathered for ground truthing in this region. In the survey area near Fehmarn a dynamic dune field was surveyed with hydroacoustic methods. This dune field is surveyed every year to document changes in the submarine environment.
    Type: Report , NonPeerReviewed
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  • 6
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    In:  UNSPECIFIED, 2 pp.
    Publication Date: 2016-08-05
    Description: 11.-15. Juli 2016
    Type: Report , NonPeerReviewed
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  • 7
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    In:  [Paper] In: OCEANS2009-EUROPE, 11.-14.05.2009, Bremen, Germany .
    Publication Date: 2018-03-15
    Description: Morphological changes in coastal areas, especially in river estuaries, are of high interest in many parts of the world. A new X-band radar on board the TerraSAR-X satellite gives access to spatial resolution as fine as 1 m. In Spotlight (SL) mode, resolution is down to 1.7 m in azimuth, with 10 × 10 km coverage. Spotlight is the best choice to monitor river estuaries, river channels, and bathymetry. Stripmap (SM) mode with a resolution down to 3.3 m and a swath width around 30 km is a perfect tool to investigate morphological features, such as coastline changes or wadden sea areas. ScanSAR (SC) mode with a resolution as fine as 18m and spatial coverage of 150 × 100 km is also used for remote sensing of coastal region and open seas. Several polarization modes allow better separation of land and water areas. For assessing the suitability of remote sensing satellite data (TerraSAR-X) to detect morphological changes, the highly morphodynamic area of the river Elbe estuary has been chosen. Morphological changes related to sedimentation, erosion and redeposition is shown by analysing in-situ data. Moreover, bottom topography retrieval can be quite efficiently demonstrated by using TerraSAR-X data compared to 1 arc-minute global relief model (ETOPO1).
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 8
    Publication Date: 2023-02-08
    Description: Submarine groundwater discharge (SGD) into coastal areas is a common global phenomenon and is rapidly gaining scientific interest due to its influence on marine ecology, the coastal sedimentary environment and its potential as a future freshwater resource. We conducted an integrated study of hydroacoustic surveys combined with geochemical porewater and water column investigations at a well‐known groundwater seep site in Eckernförde Bay (Germany). We aim to better constrain the effects of shallow gas and SGD on high frequency multibeam backscatter data and to present acoustic indications for submarine groundwater discharge. Our high‐quality hydroacoustic data reveal hitherto unknown internal structures within the pockmarks in Eckernförde Bay. Using precisely positioned sediment core samples, our hydroacoustic‐geochemical approach can differentiate intra‐pockmark regimes that were formerly assigned to pockmarks of a different nature. We demonstrate that high‐frequency multibeam data, in particular the backscatter signals, can be used to detect shallow free gas in areas of enhanced groundwater advection in muddy sediments. Intriguingly, our data reveal relatively small (typically 〈15 m across) pockmarks within the much larger, previously mapped, pockmarks. The small pockmarks, which we refer to as “intra‐pockmarks”, have formed due to the localized ascent of gas and groundwater; they manifest themselves as a new type of ‘eyed’ pockmarks, revealed by their acoustic backscatter pattern. Our data suggest that, in organic‐rich muddy sediments, morphological lows combined with a strong multibeam backscatter signal can be indicative of free shallow gas and subsequent advective groundwater flow.
    Type: Article , PeerReviewed
    Format: text
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  • 9
    Publication Date: 2021-12-08
    Type: Report , NonPeerReviewed
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  • 10
    Publication Date: 2023-07-12
    Description: Research cruise AL579 is part of the bachelor course "Physics of the Earth System - Geophysics, Meteorology and Oceanography" at the University of Kiel. It is the field exercise for marine geophysics and hydroacoustics. The aim of the annually recurring cruise is to give students a practical insight into the acquisition, processing, documentation, and interpretation of marine geophysical data. AL579 took place from August 20th -28th 2022 with the main study areas in Eckernförde Bay and the Bay of Mecklenburg. Parts of the scientific crew changed during a stopover in Kiel on Wednesday, 24.8.2022. In Eckernförde Bay we mainly collected Multibeam Echosounder (MBES) and INNOMAR Subbottom Echosounder (SES) data calibrated by CTD measurements close to the pockmark field off Mittelgrund. On Wednesday, 24.8.2022 we tested a new Ocean Bottom Seismometer (OBS) prototype. In the Bay of Mecklenburg, the focus was on Blinkerhügel and the seafloor structures further west where an enigmatic stone structure was discovered in 2021. This area was surveyed with Sidescan Sonar, MBES, SES, and CTD measurements and several video transects with an underwater drone. We also collected two sets of multi-channel seismic data to investigate the deeper structures of the Western Baltic Sea and the Bay of Mecklenburg.
    Type: Report , NonPeerReviewed
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