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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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Using a vertical line array and ambient noise to obtain measurements of seafloor reflection loss Using a vertical line array and ambient noise to obtain measurements of seafloor reflection loss

Date added: 03/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Using a vertical line array and ambient noise to obtain measurements of seafloor reflection loss. Victor Young. SR-410. March 2005.

Bottom reflection properties can be obtained from ambient noise directionality. The results obtained at six sites in 2002 with NURC’S 62m VLA are summarised. At four of the sites the VLA was moored, in order to study a single seafloor environment, while at the other two sites the VLA was allowed to drift, in order to study geographical changes in the seafloor environment. Several variants of the measurement and processing techniques are investigated here. Firstly, rather than using only the uniformly spaced central section of a nested vertical array (VLA), one can expand the useful size of the array to about three quarters (rather than one half) of the full array length by padding out the array’s correlation matrix. The padding makes the apparently good assumption that the noise crossspectral-density matrix is Toeplitz. Thus the initially sparse matrix for the outer sections of the array (with wider hydrophone separations) can be filled out with values from elsewhere in the true matrix. This provides better angular resolution which is beneficial for the method. Secondly, the possibility of synthesising a VLA with a pair of hydrophones is investigated. The benefit of a synthetic aperture would be the lower cost of the equipment in an operational context. For the process to work (without extremely long integration times) the noise source spatial distribution needs to be stationary.

An analysis of bistatic counter detection performance An analysis of bistatic counter detection performance

Date added: 09/01/2012
Date modified: 10/26/2012
Filesize: Unknown

An analysis of bistatic counter detection performance. Strode, Christopher. CMRE-FR-2012-003. September 2012.

In an attempt to maintain the upper hand in the acoustic contest be- tween sonar and submarine threat technology, navies are increasingly turning to the concept of active multistatic sensors. This technology leads to the possibility of a friendly submarine acting as a bistatic receiving platform - allowing contact range and bearing information without the need to actively transmit. The study presents a quantitative analysis of the ability of a threat submarine to counter detect the friendly receiving platform. The concept of counter detection advantage is developed and determined through acoustic analysis of environments with varying complexity.

Seabed characterization by inversion of acoustic propagation and reverberation data received on a towed horizontal array Seabed characterization by inversion of acoustic propagation and reverberation data received on a towed horizontal array

Date added: 02/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Seabed characterization by inversion of acoustic propagation and reverberation data received on a towed horizontal array. Nielsen, Peter L. ; Fallat, Mark ; Marconi, Valter. SR-417. February 2005.

Sonar performance prediction in shallow-water is highly dependent on the char-acteristics of the underwater environment. The bottom properties are critical input parameters to prediction tools and these parameters are probably the most dicult to estimate. Inversion of measured acoustic signals (direct propagation and diffuse reverberation) provides a technique to infer these bottom parameters. An ad-hoc approach using the sensors of the sonar system is proposed where the local geoacoustic properties are determined by inverting the data received on a horizontal array. The local geoacoustic properties are used as initial or guidance inputs to a reverberation model to estimate range-averaged geoacoustic and scattering properties from long-range reverberation data.

Performance modelling and validation for distributed multistatic tracking Performance modelling and validation for distributed multistatic tracking

Date added: 02/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Performance modelling and validation for distributed multistatic tracking. Coraluppi, S. SR-397. February 2005.

This report develops a distributed multi-sensor tracker performance model that accounts for the target fading effect that we observe in sea trial data. We study model-based performance as a function of key tracker parameters, the choice of tracker architecture, and the number of distributed sensors. We validate the fidelity of the model by comparing model-based performance with actual tracker performance based on simulated contact data

Using the A* path planning algorithm to assess multistatic field perfomance. Using the A* path planning algorithm to assess multistatic field perfomance.

Date added: 07/01/2009
Date modified: 08/10/2012
Filesize: Unknown

Using the A* path planning algorithm to assess multistatic field performance. Strode, C. NURC-FR-2009-010. July 2009.

The A* path planning algorithm is used to model the worst case, most intelligent threat, attempting to penetrate a multistatic barrier. The number of detections, track initiations, and overall path length are used as performance metrics. The study examines how a number of A* solutions employed against given geometries highlight potential weaknesses and may be used to guide an operator toward a more effective barrier geometry.

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