Report that covers interim results during the course of a project. Note: Unless linked to the full text, reports are only available to NATO member nations from designated distribution centres.
A look into current standardisation gaps in underwater networks. Alves, João; Pelekanalis, Konstantinos; Petroccia, Roberto. CMRE-MR-2016-016. December 2016.
This report highlights some of the key missing elements preventing underwater communications interoperability. The requirement for interoperability and standards is motivated by NATO's multi-national nature where commonalities and joint operations should be explored when possible. To establish interoperable underwater networks, a myriad of challenges must be tackled. These start on establishing common channel models and metrics, continuing all the way into defining standardised networking protocols and security policies. JANUS is introduced as an example of a standardisation effort. This document proposes extensions to the current specification looking at future revisions of the standard.
Multitarget tracking using passive acoustic arrays. Meyer, Florian; Tesei, Alessandra. CMRE-MR-2016-020. December 2016.
This report addresses the problem of localising and tracking an unknown number of targets with unknown acoustic transmit signals from Time-Difference Of Arrival (TDOA) measurements acquired by hydrophone pairs. Based on the framework of random finite sets and finite set statistics, we formulate a Bayesian estimation problem and develop a particle-based detection, localisation, and tracking algorithm that is an extension and adaptation of the Track-Oriented marginal Multi- Bernoulli/Poisson (TOMB/P) filter [1, 2]. The proposed method overcomes the challenges related to the highly non-linear TDOA measurement model, the data association uncertainty, and the uncertainty in the number of targets to be localised and tracked. We evaluate the proposed method by means of simulations and by using measurement data acquired during an experiment performed within the PERSEUS project, where a compact hydrophone array was used as a payload on a covert long-endurance Autonomous Vehicles (AV). Our numerical results confirm that the algorithm is able to determine the number of targets correctly and that it can provide accurate location estimates for static and dynamic targets and in 2D and 3D scenarios when the number of clutter measurements is moderate and the probability of detection is high. In a 2D tracking scenario, where the PERSEUS array is under water and the targets are surface vessels, the localisation accuracy in range, i.e., distance from the array, critically depends on the array depth and the distance of the target. In the fully 3D scenario, at least two PERSEUS arrays are needed for accurate target localisation. These limitations are due both to physical constrains such as the limited bandwidth of the acoustic signals and the compact size of the array and are not related to the proposed algorithm.
Report of the Third CMRE Workshop on Military Applications of Underwater Glider Technology. Borrione, Ines. CMRE-MR-2016-018. December 2016.
During the "Third CMRE Workshop on Military Applications of Underwater Glider Technology ", 26 talks were given to provide an overview of the current industrial, research and military lines of glider research and development. Three presentations were given by representatives of three of the main glider manufacturers (the French company ACSA-Alcen, the American Teledyne Webb Research and the international Kongsberg company, which is based in Norway). These have described the current abilities and applications of their gliders, providing an overview of their strengths during military applications. Engineers and scientists from international military and research centers, have provided an overview of their in-house support systems for glider operations (i.e., pre- and post-deployment, mission planning, data validation and processing) and have given examples of recent experiments involving the deployment of a single glider or a fleet of gliders with innovative payloads and sensors (i.e., reactive behaviour, acoustic payloads). Data end-users from the modeling community have introduced data assimilation techniques that are being developed to exploit the highly dense oceanographic data collected during glider operations.
Environmental assessment for tactical planning during the Glider Persistency Trial (LOGMEC16). Oddo, Paolo; Borrione, Ines; Munafò, Andrea; Russo, Aniello. CMRE-MR-2016-017. December 2016.
The impact of in-situ and remote sensed data on ocean environmental assessment procedures has been evaluated. Data collected in the framework of the LOGMEC16 (Long-Term Glider Mission for Environmental Characterization) experiment have been fused using a high resolution Ocean Observing and Prediction Systems (OOPS). The OOPS consists of a very high resolution (600m) NEMO (Nucleus for European Modelling of the Ocean) model implementation coupled with a 3D variational assimilation system. Four different experiments have been compared against available in-situ observations in terms of root mean square error and acoustic transmission loss. The first experiment does not include any assimilation scheme and has been used as reference dataset. The second experiment assimilates only the satellite derived data, Exp3 assimilates glider collected data, while Exp4 assimilates both in-situ and satellite data. Results show that simultaneous assimilation of both remote sensed and glider data provides the best results in terms of temperature and salinity error vertical distribution and acoustic characterization.
Collaborative Bayesian area clearance behavior for CAS. Munafò, Andrea. CMRE-MR-2016-022. December 2016.
Autonomous Underwater Vehicles (AUVs) present a low-cost alternative or supplement to existing underwater surveillance networks. The NATO STO Centre for Maritime Research and Experimentation is developing collaborative autonomous behaviours to improve the performance of multi-static networks of AUVs. In this work we lay the foundation to combine a range-dependent acoustic model with a three dimensional measurement model for a linear array within a Bayesian framework. The resulting algorithm is able to provide the vehicles with an estimation of the target depth together with the more usual information based on a planar assumption (i.e. target latitude and longitude). Results are shown through simulations and as obtained from the REP16 sea trial where for the first time a preliminary implementation of the method was deployed in the C-OEX vehicles.