Characteristics of permanent scatterer in coastal area

We have succeeded in estimating tide height in the coastal area with an r.m.s. error of 5.7 cm by exploiting interferometeric phase and image intensity of JERS-1 SAR data in our previous work. We used an array of oyster farming frames, composed of two vertical poles and one horizontal pole for each frame, as permanent scatterers. In this paper, we investigate the backscattering characteristics of the structure using AIRSAR data and results of experiment in laboratory. AIRSAR polarimetric images show L-band HH- and VV-polarization produce strong returns from the target structures. Classification of L-band polarimetric AIRSAR data confirms the double-bounce scatter is dominant scattering mechanism. Odd-number scatter is, however, not negligible. The ratio of single-bounce to double-bounce scattering depends of the relative radar look direction to the target array and sea surface conditions. Laboratory experiments were carried out using Ku-band according to the target scale. The results of the experiments can be summarized as: i) the structures produce a mixed signal of double-bounce and odd-bounce scatter; ii) the backscattering from horizontal pole is very sensitive to radar look direction; iii) the signals from vertical poles are stronger than that from horizontal pole. From the results, it is concluded that water level change can be most effectively estimated when vertical poles in the water are observed by L-band HH- or VV-polarization.