Passive Automatic Identification System for Maritime Surveillance

This work describes the main achievements in the Passive AIS (P-AIS) project stage. The extensive literature research in the second chapter concludes performing additional in-situ experiments to estimate reliable target RCS and clutter reflectivity values at the AIS frequency range. The typical effective RCS distribution for ferry, yacht and small wooden boat is experimentally drawn; it reaches up to 26dBsm for the ferry. A clutter model is created, taking into account the literature and the experimental study. The AIS signal waveform is analyzed and the potential range and Doppler resolution is defined. More specifically, the signal ambiguity function gives approximately 20km of range resolution and 40Hz Doppler resolution. A coverage prediction tool, based on the bistatic radar equation, including the aforementioned clutter model; bistatic geometry theory; the effective target RCS; the antenna pattern; the AIS air interface parameters is made. The tool estimates the possible P-AIS coverage area. The work concludes that: even in case of high sea state, the sea is considered as a smooth surface reflection for low grazing angle of observation in the VHF range; the equidistant SNR areas change from Cassini shape to single oval receiver centered; the AIS energy provides excellent target “visibility” if the clutter is not considered. Discussions for further clutter reduction and system sophistication are arisen.JRC.G.4-Maritime affair

I2C, Interoperable sensors & information sources for Common detection of abnormal vessel behaviours and collaborative suspect events analysis

This article presents the main user needs collected to carry out the I2C project responding to FP7 call That was issued in September 2008 for the topic: Sea Border Surveillance System. I2C project aims at setting-up a maritime surveillance system in the form of a test platform located at one specific location. This study will allow to: - test ways of data integration from a set of sensors and other available intelligent information in order to obtain optimal maritime security awareness; - Develop new algorithms and procedures for processing, using and fusing the data, from the detection up to the understanding of suspicious event and early identification of associated threats; - Discuss about the added value of the various individual sensor types. With this integrated platform, in the future, scaling studies / designs can be made that propose the composition of maritime surveillance systems at specific locations, so authorities can commission these kinds of studies based on the I2C project results. More specific goals of the project are to improve: - The monitoring of vessel movements (including non cooperative vessels) on the European sea border. This requirement imposes the deployment of additional sensors/ platforms and integrating sensor data into a common situational traffic picture; - Detection, tracking and identity/activity confirmation of cooperative vessels. - Non-cooperative vessel tracking and classification; (The last two points request to enrich the common traffic picture with intelligent information to generate a 'common intelligent situational traffic picture') - Detection of small vessels - This point requests specific sensor with small angular resolution (frequency modulation continuous wave radar would be one candidate). - Detection of suspicious behaviour (e.g. deviations from expected routes); - Understanding of intentions of vessels; - Early identification of potentially threatening situations - The last three points request specific algorithms and interpretation supporting tools to detect abnormal vessel behaviour, to understand the corresponding suspicious event, to identify the associated threat and to early report to decisional authority.JRC.DG.G.4-Maritime affair

Improvement of maritime target signatures in satellite SAR images

SAR (Synthetic Aperture Radar) signatures of maritime targets are often affected by various types of distortions, with negative impact on the classification and characterisation of the targets. Two of these distortions are defocusing and presence of sidelobes. The first one occurs when the radar returns from a scatterer are not accurately focused in a single point but spread out in the azimuth direction. The second one manifests itself around bright scatterers that are surrounded by areas with a much lower radar cross-section. Several techniques exist that try to compensate for those distortions in Single Look Complex (SLC) SAR images, but they are mostly applied to airborne SAR. This paper presents the results of applying these methods to satellite SAR.JRC.G.3-Maritime affair

MELISSA, a new class of ground based InSAR system. An example of application in support to the Costa Concordia emergency

Ground Based Interferometric Synthetic Aperture Radars (GB-InSAR) have proved to be fully operational tools for the monitoring of ground displacement and structural deformation. The main limiting factor of the existing systems is the time to acquire a single image, typically ranging from few seconds to few minutes. This paper presents the validation and the operational use of a new system – Mimo Enhanced Linear Short SAr (MELISSA), belonging to a new class of GB-InSAR devices. MELISSA is based on a Multiple Input Multiple Output Synthetic Aperture Radar (MIMO SAR) and is capable of acquiring and processing image data at an unprecedented high speed. A configuration of the system acquiring a 0.96 m synthetic aperture and 260 m swath image in 2.6 ms was tested in a controlled environment. The results prove its ability to reach an image refreshing time smaller than 4 ms and Line-Of-Sight (LOS) displacement accuracies better than 10 um. Thus, MELISSA was able to help with the monitoring of the Costa Concordia ship movements in the immediate aftermath of grounding during both the rescue operations and subsequent wreckage removal. The accurate displacement measurements of specific points of the structure are presented in a global interferogram sequence (2-D displacement maps of the whole structure). The collected data contributed to a precise wreck deformation reconstruction. MELISSA’s ability to update the information almost every second has proven to be extremely reassuring as early warning on potentially catastrophic movements.JRC.G.4-Maritime affair