Nick Walker

Ship detection with RadarSat-2 Quad-Pol sar data using a notch filter based on perturbation analysis

Target detection of marine feature is a major topic for the security and monitoring of coastlines. Synthetic Aperture Radar (SAR) has been shown to be particularly useful for this application because of its all-weather and night capability. In this paper a new ship and iceberg detection methodology is described. The algorithm proposed is based on a perturbation analysis in the target space recently developed and published by the authors [1–3], which was focused on land based target detection. The algorithm can be considered to be a negative filter focused on sea. Consequently, all the features which have a polarimetric behaviour different from the sea are detected. To demonstrate and validate the technique two RadarSat Fine Quad-Pol mode scenes were acquired off the south coast of the UK at Portsmouth harbour. An extensive ground truth campaign was also conducted that was coincident with these acquisitions. Portsmouth is one of the busiest harbours in the UK and this afforded the opportunity to capture a wide range of vessel sizes and types for analysis.

Ship detection with quad polarimetric TerraSAR-X data: An adaptive notch filter

Ship detection is a key topic for the surveillance of coastal areas and synthetic aperture radar (SAR) presents an advantageous technology for this application, because the observations cover relatively large areas and are independent of atmospheric cloud conditions and solar illumination. Recently a new generation of satellites has become available with enhanced SAR capabilities and our algorithm detects vessels by exploiting the difference between the polarimetric SAR signature of sea clutter and ships. In this paper, the algorithm that was originally used with SAR data at the C-Band frequency has been enhanced for use with high resolution X-band data such as TerraSAR-X. Moreover a dual polarimetric version of the algorithm is proposed, which has associated costs and benefits that are interesting to compare with the quad polarimetric counterpart.

Automatic ship detection in SAR satellite images: Performance assessment

This paper presents the benchmarking of four ship detection systems based on satellite borne Synthetic Aperture Radar data. This research, carried out within the framework of the FP7 NEREIDS project, provides a detailed performance assessment of the four detectors, not only in terms of detection accuracy, but also showing how they can cope with challenging situations typical of the maritime environment. Despite the good results, the conclusions are that none of the detection systems behave well in all of the conditions. Nevertheless, merging all the different ship detection reports would increase the performances.

Interferometric coherence for change detection in the Nasca region of Peru

The Nasca Lines in Southern Peru are important for their archaeological and cultural significance as well their impact on local economies as a famous tourist landmark. Recent anecdotal evidence implies that a combination of enhanced El Nino conditions and increased anthropogenic degradation are leading to the gradual erosion of the surface upon which the lines and geoglyphs are etched. A combination of barren desert, wide expanse and centimetre scale impacts makes effective mapping of such a large area very difficult. In this study it is shown that interferometric coherence using ERS data between 1997 and 1999 is sensitive to the small scale degradation across the Nasca pampa. As such it provides a potential tool for long term mapping and quantification of the degradation.

STSE SAR Ice Constellation - a backscatter simulation tool for evaluating constellations of satellites involving Sentinel-1 for ice charting

The mapping and monitoring of sea ice regions represents a key application area for spaceborne synthetic aperture radar (SAR) missions. The European Space Agency (ESA) is under-taking the development of Sentinel-1, an imaging radar mission at C-Band for the continuation of SAR operational applications. Monitoring sea ice zones and the arctic environment is one of the major application areas supported by Sentinel-1. Other spaceborne SAR missions are being developed or considered by a number of space organizations. The study described herein focuses on evaluating the contribution of SAR constellations to operational and scientific monitoring of sea ice conditions through the analysis of multi-parameter SAR datasets (airborne, spaceborne) and through the development and exploitation of a simulation tool able to predict sea ice radar signatures as a function of the ice type and condition and of sensor parameters.

A novel method for estimating offshore wind fields using synthetic aperture radar and meteorological model data

Synthetic aperture radar (SAR) provides a promising method for offshore wind field estimation, particularly in the context of important for offshore wind farm development. This paper introduces an iterative maximum aposteriori probability (MAP) method for combining meteorological model output with synthetic aperture radar for offshore wind field estimation. The MAP approach is demonstrated for 40 ENVISAT ASAR scenes collected for 2004-2006 over the UK Irish Sea. Both the CMOD4 and CMOD5 geophysical model functions are implemented and retrievals using MAP and a simpler direction based windspeed algorithm are validated against insitu mast observations. The CMOD5 MAP algorithm in particular shows promising results with an estimates on average within 2 observations.