Adrian Bodenmann

Instruments and Methods for Acoustic and Visual Survey of Manganese Crusts

This paper describes acoustic and visual instruments developed to perform high-resolution surveys of the volumetric distribution of manganese crusts from an underwater vehicle. The instruments consist of an acoustic device, developed to perform in situ measurements of manganese crust thickness at depths of up to 3000 m, and a vision-based mapping system that generates 3-D color reconstructions of the seafloor. Methods to process the information obtained by these sensors to automatically identify areas of exposed crust using the 3-D reconstructions, and subsequently determine the thickness of the crusts based on the acoustic measurements, are described. Sea trials were performed at #5 Takuyo seamount with the systems mounted onboard the remotely operated vehicle Hyper-Dolphin during the NT10-11 cruise of the R/V Natsushima. The results are that the first time in situ measurements of manganese crust thickness have been performed, and it is demonstrated that, for the types of substrate dominant in the surveyed area, continuous acoustic measurement of manganese crust thickness is possible. The work described in this paper indicates that the proposed instruments and data processing algorithms can form useful tools to enable more efficient survey of manganese crusts.

3D visual modeling of hydrothermal chimneys using a rotary laser scanning system

Hydrothermal chimneys are indicators of hydrothermal activity and therefore important in ocean research. Because of the complex terrain and suspended solids in the water around hydrothermal chimneys, it is difficult to measure them with traditional methods. In this paper we propose an innovative method to measure the shape and color of them by a rotary laser scanning (RLS) system. By combining multiple scans taken from different angles and extracting the color information from the surface of hydrothermal chimneys, we can create visual color models of them as described in figure 1. The proposed method was implemented during sea experiments in Kagoshima Bay and we were successful in reconstructing the model of a hydrothermal chimney in post processing.

Generation of high-resolution 3D reconstructions of the sea floor in colour using a single camera and structured light

Visual maps of the seafloor can provide objective information to characterize benthic ecosystems and survey the distribution of mineral deposits on spatial scales that cannot be otherwise assessed. This paper proposes a three-dimensional mapping method based on light sectioning that enables the simultaneous capture of both structure and color from the images of a single camera. The advantages of the method include high and consistent resolution of the bathymetry, and the simplicity of the setup and the algorithm used to process the data it obtains. The hardware requirements for collecting the data are a single camera, a line laser, and a light, making it possible to deploy the mapping device along with other sensors and devices on underwater platforms such as autonomous underwater vehicles and remotely operated vehicles that can log navigation data. The system has been deployed on a total of 11 cruises, among others, to survey manganese-rich crust deposits on the slopes of Takuyo #5 seamount in the Pacific at depths of more than 2,000 m. In this paper, we present the data that were obtained on one of these cruises.

Generation of High-resolution Three-dimensional Reconstructions of the Seafloor in Color using a Single Camera and Structured Light

Visual maps of the seafloor can provide objective information to characterize benthic ecosystems and survey the distribution of mineral deposits on spatial scales that cannot be otherwise assessed. This paper proposes a three-dimensional mapping method based on light sectioning that enables the simultaneous capture of both structure and color from the images of a single camera. The advantages of the method include high and consistent resolution of the bathymetry, and the simplicity of the setup and the algorithm used to process the data it obtains. The hardware requirements for collecting the data are a single camera, a line laser, and a light, making it possible to deploy the mapping device along with other sensors and devices on underwater platforms such as autonomous underwater vehicles and remotely operated vehicles that can log navigation data. The system has been deployed on a total of 11 cruises, among others, to survey manganese-rich crust deposits on the slopes of Takuyo #5 seamount in the Pacific at depths of more than 2,000 m. In this paper, we present the data that were obtained on one of these cruises.

Development of long range color imaging for wide area 3D reconstructions of the seafloor

3D visual mapping of the seafloor has found applications ranging from environment monitoring and survey of marine minerals to underwater archeology and inspection of modern man-made structures. However, the attenuation of light is significantly more pronounced in water than in air or in space, and so in order to obtain underwater images in color, it is typically necessary to be within 2 to 3 m of the seafloor. In addition to the high risk of collision when operating underwater vehicles at such low altitudes, the limited area of the seafloor covered in each image means large area surveys require a huge investment of time. In this research, we aim to increase the efficiency of mapping large areas of the seafloor by developing an underwater imaging system that can take color images at ranges of up to 13 m, so that each image can cover a larger area, together with the necessary algorithms to automatically process the data it obtains. The system was deployed to map artificial hydrothermal vents in Iheya North Knoll using the ROV Hyper-Dolphin in October 2012. In this paper, we describe the instrument and the methods used to process the data it obtains, and present wide area 3D reconstructions of habitats surrounding artificial hydrothermal vents.

Pixel based mapping using a sheet laser and camera for generation of coloured 3D seafloor reconstructions

There are several approaches for 3 dimensional mapping of the seafloor in the actual colours, many of which require multiple cameras, elaborate algorithms and specially designed vehicles. In this paper a method is presented, which uses minimal equipment and simple algorithms for this task, while treating the data in a fully 3 dimensional way from input to output. Because of the reduced hardware demands, it is well suited for combined missions, where the underwater vehicle records some other data as primary task and the map created with the proposed method acts as a support for visualising that data and the environment where it was collected.

Development of an autonomous underwater vehicle for survey of cobalt-rich manganese crust

AUV BOSS-A with visual and acoustic instrument device has been developed to survey manganese crusts located at the depth of 1,000 to 2,400 m. The AUV navigates at constant speed and altitude along waypoints with primary set, and automatically observes the seafloor by developed instruments. Visual instrument device mounted on the AUV creates 3D color reconstruction which shows the condition and the distribution of manganese crusts. Mounted acoustic instrument device is able to measure manganese crusts thickness. This paper describes the system and survey method of the AUV BOSS-A and survey results of sea trial for the demonstration of the manganese crust survey using the AUV. Survey results shows that manganese crusts with thickness of 15 to 45 mm are distributed at Katamaya sea mount. coustic instrument devices.

Pixel mapping for generation of 3D coloured seafloor bathymetry using a single camera

Visual surveys of the seafloor are often performed by robotic underwater vehicles and a number of methods exists for transforming photos or video into 2D or 3D reconstructions, most of which utilise navigation data. Laser profiling is a method that is widely used for bathymetry mapping with high vertical resolution, but typically no information of the actual colour is obtained. In this paper we propose a method for high resolution three dimensional mapping of the seafloor in colour based on laser profiling and retrieval of colour information through pixel based mapping. It employs a compact algorithm treating the data in a fully three dimensional way from input to output, which does not yield visual artifacts usually encountered when employing methods assuming planar scenes. The same hardware as for laser profiling (one video camera, a sheet laser and a navigation sensor), plus a lamp are sufficient for recording the required data. The sensors require only little space, allowing the system to be used in missions where other data is collected as the main task. Combining the 3D map with that data would allow the information to be plotted as a geographic information system (GIS) in the future.

3D colour reconstruction of a hydrothermally active area using an underwater robot

This paper extends the method introduced in [1] to generate 3D colour reconstructions of the seafloor, to account for the attenuation of light for each individual point in the reconstruction and so improve the colour accuracy of the reconstructed seafloor. The method is applied to data obtained using an AUV during the survey of a hydrothermally active area in Kagoshima Bay, Japan. The generated 3D reconstruction is compared to a 2D photomosaic taken at the same time. The results are discussed in terms of accuracy of dimensions and colour and a method to extract scientifically useful information from the 3D data is demonstrated.

Visual mapping of internal pipe walls using sparse features for application on board Autonomous Underwater Vehicles

In this project an algorithm to generate a single image of an entire water pipes inside wall was developed. An Autonomous Underwater Vehicle (AUV) equipped with a fish-eye camera will be deployed to dive through the pipe and take pictures of its inside wall. The algorithm was implemented that maps such pictures to the three dimensional model of the water pipe and based on that, generates the image that one would see if the photographed section of pipe was cut along the side and rolled out. The algorithm then uses the rolled out versions of a series of consecutively taken photos to generate a mosaic showing the entire pipe in a single picture based on the recognition of sparse, structural features. The performance of the algorithm was verified in land based experiments and the robustness of the system to measurement inaccuracy was assessed. Finally two mosaicked images were created for different paths taken through the pipe, to demonstrate that the system is capable of generating the same image, regardless of the path taken by the AUV.