Multisensor microbathymetric habitat mapping with a deep-towed Ocean Floor Observation and Bathymetry System

To describe the seafloor topography, a number of different bathymetric methods can be applied which show major differences in coverage, resolution and topographic uncertainty. In order to conduct high-resolution habitat mapping in the deep sea, subsea survey methods need to be utilised. One of those methods is the use of deep-towed sensors. This work presents the newly developed Ocean Floor Observation and Bathymetry System (OFOBS), a sensor frame with optical, acoustic and navigational sensors. With a developed processing workflow, different products are gained from post processing the collected data sets, namely submetre acoustic bathymetry, subdecimetre side-scan mosaics, subcentimetre photogrammetric microbathymetry and geometrically corrected, georeferenced submillimetre photo mosaics. The data was collected during the RV Polarstern expedition PS101 in the extreme environment of the volcanic seamounts along the Langseth Ridge in the high Arctic (87°N, 60°E).

Arctic | microbathymetry | underwater photogrammetry | deep-tow

Ausgabe: HN 110 Seite: 20–24

DOI: 10.23784/HN110-03

Autor/en: Simon Dreutter

Digital elevation models of underwater structures from UAV imagery

The paper presents a workflow for the generation of digital elevation models (DEMs) of underwater areas from aerial images. Standard software products do not provide the possibility to triangulate correctly through refractive interfaces, such as water. Known procedures are based on oriented images and known water levels with DEM determination via forward intersection based on reconstructed image ray paths (ray tracing). In this article an integrated procedure for image orientation as well as DEM extraction from aerial imagery containing both land and underwater areas is presented. The proof of concept was done by capturing UAV imagery of shallow water areas of a high-alpine lake in the Swiss Alps. The processed data set will be presented and the extraction and matching of image points observed through water are discussed. The accuracy potential as well as practical limitations of processing multimedia data are analysed.

UAV | DEM | underwater | multimedia | bundle adjustment

Ausgabe: HN 110 Seite: 14–19

DOI: 10.23784/HN110-02

Autor/en: Christian Mulsow

Mass wasting in Lake Constance – A GIS-based geo-morphometric reconnaissance

New high-resolution hydroacoustic data from the »Tiefenschärfe« project in Lake Constance (central Europe) reveals a large amount of mass wasting events occurring on all slopes and influencing large parts of the lake floor. Within a GIS-supported geomorphologic investigation, a manual picking of mass transport deposits, as well as a digital reconnaissance were carried out, based on the visual appearance of mass transport deposits and on elevation-derived morphometric parameters, respectively. Subjective manual and objective (semi-)automatic detection strategies show the usability of the latter to be a new, easy-to-use assistive tool for identifying mass transport deposits in large bathymetric data sets and quantifying the morphological imprint of events on the lake floor. The iteratively determined algorithm divides mass wasting occurrences into the sub-features break-off edge, transport channel and depositional lobe and suggests morphometric dependencies for each sub-feature. Because Lake Constance consists of three mutually independent subbasins the algorithm success differs somewhat, which we credit to locally changing hydrodynamic and sedimentologic patterns.

Lake Constance | bathymetry | mass wasting | morphometry | GIS

Ausgabe: HN 110 Seite: 8–12

DOI: 10.23784/HN110-01

Autor/en: Nils Brückner, Paul Wintersteller, Martin Wessels, Stefanie Gaide

A keystone in the defence oceanography community

As a scientist at the Underwater Acoustics and Marine Geophysics Research Institute of the German Federal Armed Forces (FWG) Thomas Wever has left remarkable traces with his contributions to the international research community. Above all the organisation of a symposium called »The Ocean’s Seafloor – One Bio-Geo System« was a gift to his colleagues. The results of this superb conference in October 2016 in Hannover are still resonating.

Ausgabe: HN 109 Seite: 50

DOI: 10.23784/HN109-11

Autor/en: Chris Jenkins

In memoriam Dr. Thomas Wever

Am Samstag, dem 28. Oktober 2017, verstarb nach langer und schwerer Krankheit Herr Dr. Thomas Wever im Alter von 59 Jahren. Der Wissenschaftler bei der WTD 71 im Forschungsbereich für Wasserschall und Geophysik (FWG) in Kiel war schon lange krank, dennoch kam sein Tod für seine Kollegen und Freunde unerwartet, da er bis zuletzt zuversichtlich war, die Krankheit besiegen zu können.

Ausgabe: HN 109 Seite: 48–49

DOI: 10.23784/HN109-10

Autor/en: Wolfgang Maier