Depending on their height above the sea surface and on the ship's distance to the radar, the RCS of scatterers that form the ship's signature is influenced considerably by multipath. Based on measurements that were taken at 35 GHz of an outgoing ship between 1 km and 30 km distance it is demonstrated how the high range resolution profile of the ship and consequently any length estimate derived therefrom is modified by multipath as a function of range. Combining several channels by means of polarimetry can mitigate these effects and thus stabilize the estimates of any scatterer based features including 'length'. The TERPEM software is used to simulate the effect and to compare modeled and measured results. As a first step towards the classification of ships, one of the most obvious features, namely the length of a ship, was analysed w.r.t. effects like multipath and the influence of sea clutter. Two different methods to determine length were analysed and compared to each other. The influence of multipath could be clearly demonstrated, especially in cases where dominant scatterers near the extremes of the ship (bow, stern) are extinct due to interference. It could be further demonstrated that the effect of LE fluctuations can be mitigated either by temporal integration or by making use of polarimetry. The latter yields more realistic estimates and provides more samples during each time-on-target. All approaches have in common that the length estimate usually is smaller than the physical/geometric range extent of the target due to self-masking effects at low depression angles. In view of the pronounced differences between the two approaches further analysis is necessary to understand how the structure of the HRR profile in connection with the surrounding clutter influences the length estimate. Also, more different features based on the geometry of scatterers within the HRR profile should be analysed in the future. Using CAD models of known ships in connection with TERPEM predictions of multipath effects might at length enable a reliable prediction of expected HRR profiles and thus facilitate ship recognition by comparing measured with predicted profiles.


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    Title :

    The influence of multipath on the classification of ships


    Additional title:

    Einfluß der Mehrwegausbreitung auf die Schiffsklassifizierung


    Contributors:


    Publication date :

    2009


    Size :

    5 Seiten, 6 Bilder, 2 Tabellen, 7 Quellen


    Remarks:

    (nicht paginiert)


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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