KRIEGERS FLAK OWF GEOPHYSICAL SURVEY ... - Energinet.dk

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KRIEGERS FLAK OWF GEOPHYSICAL SURVEY RESULTS 10 No seabed vegetation were identified across the area in the side scan sonar and bathymetric records, hence no areas of biological interest were identified. KF_OWF_Geophysical_Survey_Results_v4.docx
KRIEGERS FLAK OWF GEOPHYSICAL SURVEY RESULTS 11 8. TARGETS Targets lying on the seabed have been identified in the records of the side scan sonar and bathymetric as well as gradiometer (consisting of two magnetometers). The side scan sonar and bathymetric sensors identifies targets by emission and reflection of sound waves, whereas the gradiometer detects targets of ferromagnetic origin. Based on Ramboll DK’s assessments during the processing, interpretation and presentation of the side scan sonar plus bathymetric as well as gradiometer data, it is most likely the positions of the interpreted targets meets the required IHO 5E 1a accuracy as outlined in section 3. The following classifications have been used when identifying targets: Linear Sonar Targets Sonar Targets Boulders Depression As found wreck Magnetic Anomaly Targets with dimensions greater than ½ m in any direction have been picked, however due to higher resolution of the various sensors close to the vessel; some minor boulders close to the vessel have been picked, as well. Targets which obviously did not relate to geology based on their sonar appearance were classified as Man-Made. This could be features which are long and thin or square in shape and otherwise if not possible to classify, they were classified as unidentified Sonar or Linear Sonar Targets depending of shape and distribution. Seabed features with sonar appearance as a boulder were classified as Boulders. A total of 4,250 targets in total were identified in the side scan sonar and bathymetric records. 16 targets are potentially of man-made origin and all others have been assigned as boulders, which are dominant in the record, some of which measure up to 10m in diameter. A total of 935 magnetic targets in total were identified across the Kriegers Flak OWF site. 3 targets are a coinciding with the locality to the 3 observed wrecks (see section 9) and 46 are associated with seabed infrastructure (see section 8.1). 685 targets are classified geological and all (201) other anomalies are unclassified/unidentified. It is likely that in many cases the anomalies are a function of the ferrous properties of the observed boulders. This interpretation is supported by the fact that the areas of high density of Magnetic Anomalies (Figure 8-1) coincide with areas classified as Glacial Till with Numerous Boulders (Figure 7-1). The anomalies associated with infrastructure denote the location of the Baltic Cable, which was clearly detected to the west of the site running north-south. These detections help validate the other geophysical records and enable the derivation of an ‘as found’ position for the infrastructure. Figure 8-1 provides an overview of targets picked on the side scan sonar and bathymetric as well as gradiometer data at the Kriegers Flak OWF site. KF_OWF_Geophysical_Survey_Results_v4.docx
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