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Fachbeiträge

Sämtliche Fachbeiträge aus den Hydrographischen Nachrichten seit der Ausgabe HN 100 sind online verfügbar.
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Offshore unexploded ordnance recovery and disposal

Millions of tons of unexploded ordnance (UXO) and discarded explosive remnants from war can be found in European waters and beyond. Many of them are next to the shoreline, dispensing toxics to the environment. Dumping of ammunition, military practice and warfare are the main source for this large amount posing a risk for the offshore industry besides the undeniable impact this also causes to the environment. With increasing utilisation of offshore areas, the activities in offshore UXO clearance have increased. Due to the governmental commitment and planning of increased usage of offshore wind energy in Germany, research has been conducted to solve the technical question of unexploded ordnance recovery and disposal. Within the last five years, the market for offshore UXO detection and removal has multiplied as well as experience increased, research has also lead to better analytical results during the UXO survey campaign which has helped achieve fewer false alarms. Better techniques and the development of specialist equipment for the removal results in smaller time frames in which the clearance can be done as well as lower risk for equipment and personnel. Research is also being conducted on how to handle ammunition safely which is classified as not save to transport without the normal demolition procedure.

UXO | unexploded ordnance | investigation | metal detector | recovery | disposal | underwater positioning

  • Ausgabe: HN 105 Seite: 40–42
  • DOI: 10.23784/HN105-08
  • Autor/en: Jan Kölbel, David Rose

Improved positioning of surveying vessels on inland waterways with HydrOs

Surveying vessels are equipped with GNSS receivers or GNSS-INS coupled systems respectively to determine their position. By receiving and processing a correction signal, which is provided by a network of continuously operating reference stations, they determine a precise GNSS real-time kinematic (GNSS-RTK) solution. Thereby, the multibeam echo sounder observations can be georeferenced in order to produce a map of the channel bottom. One crucial point of the entire workflow is the quality of the vessel position which is highly influenced by the surrounding topography. For instance, bridges or buildings can cause multipath effects, refraction or a complete loss of signal reception. Often, even the correction signals cannot be received. Then, no RTK solution can be determined. To mitigate such gaps in the GNSS-RTK trajectory, an adjustable multi-sensor system called Integrated Hydrographic Positioning System (HydrOs) was developed as a joint project of the German Federal Institute of Hydrology (Bundesanstalt für Gewässerkunde) and the Institute of Engineering Geodesy at the University of Stuttgart.

GNSS | positioning | Extended Kalman Filter | hydrographic multi-sensor system | outlier testing

  • Ausgabe: HN 105 Seite: 34–38
  • DOI: 10.23784/HN105-07
  • Autor/en: Thomas Artz, Annette Scheider, Marc Breitendeld, Thomas Brüggemann, Volker Schwieger, Harry Wirth

ENC and ECDIS

Electronic Navigational Charts (ENC) and Electronic Chart Display and Information Systems (ECDIS) are typically created at different places: ENCs by various hydrographic offices, ECDIS by various industrial ECDIS manufacturers. When in use, ENCs and ECDIS form a closely interconnected »community« with its members strongly dependent on each other when creating results which aim to support the navigator as efficiently as possible. Recognising the complexity of the standardisation task a great deal of success has been achieved in creating a worldwide community of producers and users of ECDIS and ENCs providing a global coverage for the international maritime community. However, gaps exist between worlds of ENCs and ECDIS with regard to the standards and methods applied when producing and using ENCs and ECDIS. Some of these discrepancies between the worlds of ENCs and ECDIS have the potential to mislead the navigator and other users.

ENC | ECDIS | bathymetry | zooming in | S-57

  • Ausgabe: HN 105 Seite: 30–33
  • DOI: 10.23784/HN105-06
  • Autor/en: Peter Dugge

Use of laser bathymetry at the German Baltic Sea coast

The German coastal waters are quite shallow. The idea arose to use airborne laser bathymetry (ALB) for hydrographic surveying of near-shore areas of the German Baltic Sea. Since these waters are relatively turbid, it became necessary to investigate to what extent modern ALB systems could be of practical use in an area large enough for hydrographic purposes especially in the Baltic Sea. The basic questions to be answered by the project were: Which areas can be measured by this method? And how expensive will this be in relation to traditional methods? From 2012 to 2014, four test surveys have been accomplished in an area north of the city of Wismar. During these surveys, many relevant questions were solved.

ALB | laser bathymetry | Baltic Sea | Secchi depth

  • Ausgabe: HN 105 Seite: 26–28
  • DOI: 10.23784/HN105-05
  • Autor/en: Wilfried Ellmer

New techniques in capturing and modelling of morphological data

Since 2014 the techniques of LiDAR bathymetry have been used for capturing morphological data in Schleswig-Holstein. Round 2000 km. have already been surveyed with these techniques. Data gaps only occur locally in tide ways or low-lying areas, which are needed to be filled by hydrographic surveys. But compared with the bathymetric LiDAR, these surveys have a substantially lower density of points. Hence, it is difficult to merge these data to a morphological model. As a consequence it is necessary to densify the hydrographic data to create a homogeneous model. The mathematical method of Coons patches is suitable for this purpose. The gaps inside the area of hydrographic survey are filled with data points in desired density. The bathymetric information is then calculated using bilinear interpolation. As a result a data set which has a similar point density as the bathymetric LiDAR is created. After the preparation a homogeneous morphological model can be generated by triangulation, based on bathymetric LiDAR on the one hand and hydrographic surveys on the other hand.

coastal protection | LIDAR bathymetry | morphological data model | Coons patches

  • Ausgabe: HN 105 Seite: 22–25
  • DOI: 10.23784/HN105-04
  • Autor/en: Lutz Christiansen

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