Analysis of High Grazing Angle Sea-clutter with the KK-Distribution

An estimated probability distribution of the backscatter is commonly used to determine the threshold for distinguishing targets from clutter at a given false alarm rate. Data collected at high grazing angles (15◦−45◦) by the Defence Science Technology Organisation’s Ingara fully polarimetric X-band radar demonstrates that the commonly used K-distribution is not always adequate for modelling the probability distribution. This is especially the case for the horizontal polarisation when sea-spikes can cause high false alarm rates. An alternative proposed as a more accurate model is known as the KK-distribution. The analysis presented in this report describes this model with the addition of multiple looks and a thermal noise component to produce an estimate of the underlying mean and shape. This then enables the KK-distribution to be used as a proxy for data in radar detection performance studies. The threshold required to achieve a constant false alarm rate is then studied and compared with that obtained from the K-distribution. APPROVED FOR PUBLIC RELEASE