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Space Eye

London Research and Development Corporation develops software exploitation tools for high resolution Synthetic Aperture Radar (SAR) imagery from satellites, such as RADARSAT-1 and -2. As well as shipping, Maritime Domain Awareness requires a knowledge of the environment near the sea surface, for example wind field retrieval. Information about ships can be found from SAR and from self reporting, such as AIS. Ship wakes are often seen in SAR images and promise to be an important source of useful data for verifying ship reports. Personnel have contributed to the theory of SAR ship wakes and AIS.
  • MDA Expertise
  • Space-Eye Image Exploitation Tool
  • Envisat, RADARSAT-1 and -2 High Resolution Wind Field Extraction/Retrieval
  • Ship Detection Algorithms
  • Ship Wake Analyses
  • Ship Wake Simulation
  • Integration with AIS
Wind field retrieval from RADARSAT-1 ScanSAR image of the Gulf of Mexico; produced by Space-Eye Wind and Waves application.

Space-Eye Image Exploitation Tool

  • Satellite sensors provide a wide area surveillance capability and radar, operating between 1 GHz and 10 GHz, is not constrained by cloud cover and is not affected by a lack of sunlight. Satellite borne Synthetic Aperture Radar (SAR) is capable of high resolution. For example, images in the ScanSAR Narrow mode of RADARSAT-1 and -2 have a swath width of about 300 km and a resolution cell size of about 75 m.
    The wind speed and direction relative to the SAR affect the ocean surface radar backscatter cross section; models, such as the CMOD family, exist to describe the functionality and are included in the Space-Eye wind retrieval application. If the wind direction is given, these models can usually be inverted uniquely to yield a wind speed from a radiometrically calibrated SAR image. The wind direction can be obtained by detecting quasi-periodic structures in the radar image; these streaks are often associated with boundary layer rolls. There is a fundamental 180 degree ambiguity in the wind direction that must be resolved either visually from shadowing or from some other source, such as ASCAT. Therefore an external direction must be entered and this is used to determine the sense of the wind vectors after extraction: see the retrieved wind field product depicted below. For ScanSAR narrow or Wide images, there are typically many wind direction extractions.
    A land mask in ESRI polygon shape file format is often required. This can be supplied for limited areas.
    In addition, ocean waves modify the radar backscatter coefficient and information about the direction of the sea and the significant wave height can be extracted.
    A disadvantage of satellite borne sensors, including RADARSAT, Envisat, etc., is often the lack of persistent surveillance because, with each satellite, a small area of the earth's surface at low and mid-latitudes can only be imaged once every few days. However, the high resolution of SAR can be more important for some naval and commercial applications.
  • Space-Eye is a software application to retrieve or extract a wind field product (the vectors representing direction and speed) from a SAR image. Accepted CMOD models (the default is CMOD4) are employed. Currently the satellites RADARSAT-1, RADARSAT-2, Envisat and PALSAR are supported by the Space-Eye application, though the code for TerraSARX is under development.
    The wind speed is found with a resolution of better than 1 km, which is higher than is typical of satellite borne scatterometers.
    The Space-Eye wind extraction application is designed to function using commonly available commercial imagery with the emphasis on wide swaths. For example, RADARSAT imagery can be obtained from MDA Geospatial Services or produced by the Scanex processor. Space-Eye is currently in operational use. The data can be saved as a ".csv" file that can be loaded into other programs such as Excel and ArcGIS.
  • The extracted SAR wind field product shown below is from RADARSAT-2 (Los Angeles). Notice that the wind directions vary over the plot and are consistent with shadowing by the islands. Another example of a Black Sea wind retrieval product using a Scanex processed RADARSAT-1 image is shown in SAR Wind-Field Product of the Black Sea. An example of an Envisat wind retrieval is shown in SAR Wind-Field Product of Hawaii from Envisat (Data provided by the European Space Agency).
Space-Eye wind retrieval product derived from RADARSAT-2 image off Los Angeles.