Roy Edgar Hansen

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The heavy-tailed multivariate normal inverse Gaussian (MNIG) distribution is a recent variance-mean mixture of a multivariate Gaussian with a univariate inverse Gaussian distribution. Due to the complexity of the likelihood function, parameter estimation by direct maximization is exceedingly difficult. To overcome this problem, we propose a fast and(More)
This paper presents signal processing techniques particularly suited for interferometric Synthetic Aperture Sonar (SAS) systems onboard Autonomous Underwater Vehicles (AUV) (or other platforms carrying high grade navigation systems). The signal processing is applied to data collected in a controlled rail experiment at Elba Island, Italy, using a wideband(More)
The success of synthetic aperture sonar (SAS) is critically dependent on overcoming several challenges. The sonar has to be positioned with accuracy better than a fraction of a wavelength along the synthetic aperture. The ocean environment, and particularly the sound velocity, has to be accurately estimated for successful focusing of SAS images. For(More)
Successful synthetic aperture sonar (SAS) imaging is dependent of several challenges to be overcome. The sonar has to be positioned with accuracy better than a fraction of a wavelength along the entire synthetic aperture. At 100 kHz this equals an accuracy requirement around 1 millimetre along tens of metres of travelled distance. The ocean environment, and(More)
Synthetic aperture sonar (SAS) interferometry can provide bathymetric maps of the seafloor with high resolution over large swaths. Traditional narrowband interferometry relies on advanced phase unwrapping techniques to resolve phase ambiguities. For wideband systems there are alternative techniques to estimate the absolute (or ambiguity-free) phase(More)
The heavy-tailed Multivariate Normal Inverse Gaussian (MNIG) distribution is a recent variance-mean mixture of a multivariate Gaussian with a univariate inverse Gaussian distribution. Due to the complexity of the likelihood function, parameter estimation by direct maximization is exceedingly difficult. To overcome this problem, we propose a fast and(More)
Collection of synthetic aperture sonar (SAS) data along a circular track and forming a circular SAS (CSAS) image has several benefits over traditional stripmap SAS: the area of interest is observed from all aspect angles giving a better perception; the resolution in the image increases and shadow zones are avoided. Navigation requirements however, become(More)
Synthetic aperture sonar (SAS) is emerging as an ideal sensor for autonomous underwater vehicle (AUV) based mine hunting and numerous other applications. By using vehicle motion to create a long synthetic array, image resolution can be increased by an order of magnitude or more compared to traditional side scan sonars. The SAS technology is also well suited(More)
The minimum variance (MV) beamformer, also known as the Capon or minimum variance distortionless response (MVDR) beamformer, uses the recorded wavefield to compute a set of optimal weights to be applied to each sensor, before coherently adding the sensor outputs. The weights are chosen such that the variance of the output is minimized while maintaining unit(More)
Over the last few decades, a range of instruments and vehicles have been used to monitor the oceans. One example is the use of autonomous underwater vehicles to perform ocean surveys, and within this group, autonomous underwater gliders have made their mark. Gliders enable the scientist to make extended complex studies on topics such as the effect of(More)