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Formal Reports

Report of results of completed projects or major milestones either in scientific terms or in terms acceptable to a wider audience. Note: Unless linked to the full text, reports are only available to NATO member nations from designated distribution centres. 

Documents

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The Multi-Scale multi-model Super-Ensemble cocktail: break, shake and mix The Multi-Scale multi-model Super-Ensemble cocktail: break, shake and mix

Date added: 04/01/2006
Date modified: 06/22/2012
Filesize: Unknown

The Multi-Scale multi-model Super-Ensemble cocktail: break, shake and mix . NURC-FR-2006-009. April 2006.

Nowadays, an increasing number of models are routinely providing weather forecasts and climate predictions, offering multiple options on resolutions, range domains and derived fields. On the other hand, NATO requirements are based on one scene-one forecast strategies for operational planning, complemented by small scale, short period environmental forecasts and analysis for tactical support. This fact poses two fundamental problems: from the multiple available forecasts which one should be used; and what is the accuracy and reliability of the products used for tactical support. These issues become more challenging and relevant when considering support for Expeditionary Warfare (in remote areas with limited access) and countering naval asymmetric warfare (need for high accuracy and reliability). The multi-model Super-Ensemble (SE) technique which uses an optimised combination of an ensemble of models has previously been demonstrated to improve forecast skills in atmospheric and ocean models over simple - and bias-removed - ensemble means, further improved using dynamic, regularization, non-linear or probabilistic techniques. A significant drawback of this method for systems which have specific peak frequencies, like well identified geophysical processes for example, is that it does not allow a process-wise combination of models, i.e. the weight on a model is constant whatever the process. Here we show that, by decomposing the individual models into their most relevant spectral bands and re-combining them carefully, this Multi-Scale multi-model Super-ensemble (MSSE) approach outperforms traditional SE forecast skills and allows recovering high frequency phenomena usually averaged out by SE, which offers potential new improvement in atmospheric and oceanographic modelling, uncertainty estimation and data fusion.

Multistatic active sonar system interoperability, data fusion, and measures of performance Multistatic active sonar system interoperability, data fusion, and measures of performance

Date added: 04/01/2006
Date modified: 06/22/2012
Filesize: Unknown

Multistatic active sonar system interoperability, data fusion, and measures of performance. NURC-FR-2006-004. April 2006.

Anti-submarine warfare operations are increasingly challenged due to the quiet nature of current threat submarines, and the complexity of shallow water acoustic environments in which they must be conducted. Active sonar systems have become an important addition to passive systems in the detection of submarines under such conditions. However, active sonar systems must be able to overcome unfavorable propagation conditions, high levels of obscuring reverberation, and increases in the amount of confusing target-like false alarm clutter. Multistatic active sonar configurations have been proposed as a way to augment ASW capability over standalone monostatic active sonar. Over the past several years, the NATO Undersea Research Centre and its collaborators have been engaged in conducting research into the multistatic active sonar system concept. Several at-sea multistatic research trials have been conducted and much knowledge has been gained into the system concept’s performance, interoperability requirements, potential for effective data fusion, and measures of performance. This has resulted in significant number of detailed technical reports and papers on various aspects of the subject. This work is summarized, with an extensive listing of references provided for the reader who requires more detailed treatment of the subject or wishes to obtain specific real world examples based on recent multistatics experiments conducted at sea.

Multipath pulse shapes with refraction Multipath pulse shapes with refraction

Date added: 04/01/2006
Date modified: 06/22/2012
Filesize: Unknown

Multipath pulse shapes with refraction. NURC-FR-2006-005. April 2006.

All long range sonars have to contend with the effects of multipath propagation. One effect is that an impulse from a remote source or a reflected impulse from a point-like target will be significantly broadened. For example, in isovelocity water it has already been shown that one expects the tail of the pulse to fall off linearly in dBs with a decay constant that depends only on the bottom reflection properties and does not depend on the range of the target. Furthermore if neither sonar nor target have significant vertical directionality then the pulse shape is independent of their properties too. This finding has important implications for the design of sonars since integration times need to be matched to the characteristic arrivals of a target in its environment. The benefit of analytical solutions is that behaviour becomes immediately clear without having to cover an ndimensional parameter space. In addition one can make generalisations which would otherwise be impossible. This report extends the work to investigate the effects of upward or downward refraction. The known angle behaviour of the multipath arrivals can be converted into a time dependence to reveal the multipath pulse shape for a remote source (one-way path) or a target (two-way path). Exact solutions can be calculated numerically, explicit closed-form approximations are given for oneway paths, and these are converted to two-way paths by numerical convolution.

Modern minehunting techniques and the MCM EXPERT software Modern minehunting techniques and the MCM EXPERT software

Date added: 04/01/2006
Date modified: 06/22/2012
Filesize: Unknown

Modern minehunting techniques and the MCM EXPERT software. NURC-FR-2006-011. April 2006.

Side-scan sonars are increasingly being used to perform detection and classification in minehunting operations. The current NATO Mine Countermeasures (MCM) software tool, MCM EXPERT, provides support for the planning and evaluation of minehunting operations, but was developed for MCM units having forward-looking sonar. The NATO Undersea Research Centre (NURC) has initiated a project to provide the capability to accurately plan and evaluate minehunting operations using side-scan sonars and Autonomous Underwater Vehicles (AUVs). As part of this project, a complete review of the MCM EXPERT algorithms was undertaken in order to evaluate their applicability to modern minehunting systems using AUVs and side-scan sonars. Based on a review of the current algorithms, the NURC have provided a set of interim recommendations for the use of MCM EXPERT with side-scan sonars. Certain pre-conditions, which have been documented in this report, must be met for MCM EXPERT to be used to plan and evaluate minehunting missions using side-scan sonars. In addition, limitations in the accuracy of the results obtained when using MCM EXPERT for side-scan sonar are stated.

Algorithms for Decision Aid for Risk Evaluation (DARE) version 2.1 Algorithms for Decision Aid for Risk Evaluation (DARE) version 2.1

Date added: 04/01/2006
Date modified: 06/22/2012
Filesize: Unknown

Algorithms for Decision Aid for Risk Evaluation (DARE) version 2.1. NURC-FR-2006-002. April 2006.

Decision Aid for Risk Evaluation (DARE) is a software tool for assessing the risk to transiting vessels after Maritime Mine Countermeasures (MCM) have taken place. The DARE software has been used in NATO Exercises since 1997. The software has been updated and improved to reflect the needs of the NATO navies. In order to estimate the risk to naval traffic, DARE uses information on the mines countered during MCM Operations, along with the "percentage clearance," or the probability estimate of having countered any given mine. DARE is a command level tool developed to provide an estimate of risk in the case where there may be several units working together and where the mine threat cannot be attributed to a single mine type. Another NATO software tool, MCM EXPERT, can be used to assist units in Planning and Evaluating tasks, and to provide the percentage clearances required by DARE. The NATO Undersea Research Centre has been responsible for the previous two versions of DARE. Version 2.0, released in May 2004, was entirely revised from the previous release (DARE98) and included a new Graphical User Interface, an updated algorithm, and an optimized calculation method which greatly increased the size of scenarios that could be calculated. DARE version 2.1 was released in December 2005. In addition to new software functionality, this version has additional algorithms which can be used to handle the case of multiple transitors. This document provides a comprehensive treatment of the algorithms used in DARE version 2.1.

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