Zbigniew Lubniewski

A novel method for archiving multibeam sonar data with emphasis on efficient record size reduction and storage

Abstract Over the past few years considerable advances in sonar technology, spatial positioning capabilities and computer processing power have lead to significant improvements in mapping, imaging and technologies of seafloor exploration. Recently, modern multibeam echosounder systems (MBES) capable of recording backscatter data for the whole water column, not just for the seabed, have become available thus providing data allowing for visualization and analysis of objects other than the seabed such as single fish, fish schools or pollution. Unlike bathymetric sonars, which only capture the seafloor, multibeam systems produce very large amounts of data during surveys. Because of this, storing the data collected during hydrographic or scientific cruises becomes a crucial problem. In this context, the paper proposes a new approach for efficient reduction and storage of MBES records. The results of a sample implementation of the algorithm being tested on several different sets of MBES data are also discussed.

Geographical Information System for analysis of Critical Infrastructures and their hazards due to terrorism, man-originated catastrophes and natural disasters for the city of Gdansk

The paper presents a web-based Geographic Information System (GIS) for assessment and visualization of Critical Infra structure (CI) and its hazards which was developed by the Department of Geoinformatics at Gdansk University of Technology for the City of Gdansk. The system allows spatial processing and mapping of various CI analysis results, with the CI analysis module based on the CARVER2™ technology adapted to particular requirements of the Gdansk City Hall Crisis Management Department (CMD). The system works as an integrated solution for both visualization of hazard scenarios and a team-enabled environment for information analysis and sharing among geographically distributed decision makers. The paper focuses on the sample applications with reference to the analysis, visualization, and mapping in a geographical context of several threat scenarios, such as blast attack, chemical attack, and toxic leakage as well as the spatial distribution of critical infrastructure components in Gdansk, Poland.

Seabed classification using multibeam echosounder

The method of seabed identification and classification from multibeam sonar echoes is presented. The proposed approach is based on calculation of a set of parameters of an echo envelope, similarly as in seafloor classification using single beam echosounder. These parameters are extracted for each consecutive beam allowing the estimation of their dependence on the seafloor incident angle. The relation between seabed type and calculated echo parameters and its angular dependence, is investigated. The results obtained using sonar data records from several bottom types in Gdansk Bay water region are presented and discussed.

Using angular dependence of multibeam echo features in seabed classification

The approach to seabed classification based on processing multibeam sonar echoes is presented. The multibeam sonars, besides their well verified and widely used applications like high resolution bathymetry measurements or underwater object imaging, are also the promising tool in seafloor identification and classification, having several advantages over conventional single beam echosounders. The proposed seabed classification method assumes calculation of a set of parameters of an echo envelope, similarly as in single beam classification. These parameters include echo energy, echo length, statistical moments of echo energy and the set of echo shape descriptors. They are extracted for each consecutive beam allowing the estimation of their dependence on seafloor incident angle. The characteristic features of this dependence are described quantitatively and constitute the input information for an automatic supervised seabed classifier. The results of the simple classification procedure applied for multibeam d...

GIS for remote sensing, analysis and visualisation of marine pollution and other marine ecosystem components

Pollution detection, environment sensing and appropriate response strategies are important due to the marine ecosystemspsila continuous absorption of pollutants of various origins. Several approaches and techniques of measurements are available for marine environment monitoring including direct sampling, airborne and satellite imagery and underwater acoustics. The huge development in the information technology has provided the possibilities for much faster and more efficient access to survey data, allowing their remote, nearly real-time management, processing and visualisation. The proposed GIS is able to integrate many different types of marine pollution survey data, especially those acquired by various acoustic sensors like Multibeam Sonar Systems (MBSS), echosounder and Side Scan Sonars (SSS). It also supports instantaneous 2D and 3D visualisation in the form of thematic layers that can be overlaid. The system utilises the ArcSDE application server that facilitates storing and managing spatial data (raster, vector, and survey) in a database and ArcGIS Engine GlobeControl and MapControl components for georeferenced presentation of various objects. The set of geoprocessing and spatial analysis methods can be used in order to retrieve relevant information and analysis results.

Application of Shape From Shading Technique for Side Scan Sonar Images

Abstract Digital signal processing technology has revolutionized a way of processing, visualisation and interpretation of data acquired by underwater systems. Through many years side scan sonars were one of the most widely used imaging systems in the underwater environment. Although they are relatively cheap and easy to deploy, more powerful sensors like multibeam echo sounders and sonars are widely used today and deliver 3D bathymetry of sea bottom terrain. Side scan sonar outputs data usually in a form of grey level 2D acoustic images but the analysis of such pictures performed by human eye allows creating semi-spatial impressions of seafloor relief and morphology. Hence the idea of post-processing the side scan sonar data in a manner similar to human eye to obtain 3D visualisation. In recently developing computer vision systems the shape from shading approach is well recognized technique. Applying it to side scan sonar data is challenging idea used by several authors. In the paper, some further extensions are presented. They rely on processing the backscattering information of each footprint (pixel in sonar image) along with its surroundings. Additionally, a current altitude is estimated from the size of shadow areas. Both techniques allow constructing 3D representation of sea bottom relief or other investigated underwater objects.

Nearly real-time, safety-related, remotely accessible marine GIS

The paper presents the prototype of safety-related application of the newly developed real-time, remotely accessible marine GIS for water pollution monitoring and emergency management supporting. The system is able to integrate many different types of marine pollution survey data, including those acquired by acoustic sensors. It processes the data extracted from acoustic echo signals and supports the instantaneous 2/sup D/ and 3/sup D/ visualisation and mapping of pollution aggregations (oil spills, discharge material plumes etc.). It also deals with the multi aspect data management and data analysis, and the prediction of the pollutants behaviour. The system makes use of the SQL database standard for data storage and the Scalable Vector Graphics (SVG) and Virtual Reality Modelling Language (VRML) for geographical objects remote presentation. Moreover, it requires only the WWW browser with SVG and VRML plug-in on the client side.

The comparison of inverse filtering techniques applied together with fractal analysis in the sea bottom recognition

The results of the combined approach using fractal analysis and inverse filtering methods applied to sea‐bottom‐type recognition are presented. The single‐beam one‐frequency echosounder was used in described investigations. The bottom‐scattering impulse response was used to extract descriptive parameters of a seabed type. Both direct methods, including windowed SVD, regularization and wavelet analysis, as well as iterative techniques like maximum entropy, and expectation, maximization, and smoothing (EMS) were investigated. The data were acquired from acoustics surveys on Lake Washington and Liberty Bay. The results were compared and discussed especially in the context of excessive smoothing of the extracted fractal features by applied newly developed inverse techniques.

The modeling of acoustic wave scattering on fractal seabed surface

The one‐dimensional model of a plane wave scattering on a corrugated seabed surface was analyzed in order to investigate the process of transferring the fractal structure of the bottom surface onto bottom scattering impulse response. The investigation evaluates the adequacy of the fractal dimension of a bottom impulse response as a descriptive parameter of a bottom type. The Kirchhoff approximation was used in the model. Several types of sea bottom surfaces with different fractal dimensions were used in modeling and the relation between fractal dimension of a bottom surface and fractal dimension of its impulse response was found.