Wavelet-based coding of three-dimensional oceanographic images around land masses

We describe an algorithm for the embedded coding of 3D oceanographic images. These images differ from those arising in other applications in that valid data exist only at grid points corresponding to the sea; grid points that cover land or lie beyond the bathymetry have no associated data. For these images, we employ a 3D lifting wavelet transform tailored specifically to the potentially sparse nature of the data by processing only the valid sea data points in between land masses. In addition, we introduce successive-approximation runlength (SARL) coding, an embedded-coding procedure which adds successive-approximation properties to the well known stack-run (SR) algorithm. SARL is a general technique applicable to the oceanographic images considered here as well as to other coding tasks in which embedded coding is desired but for which zerotree-techniques are impractical.