Sound radars provide valuable information on the characteristic patterns of atmospheric boundary layer (ABL). The ABLs are, however, often corrupted and broken due to various noises present in the sodar imageries. This often leads to wrong interpretation of the image. Standard image-processing techniques do not seem to remove these noises adequately. In our present work, we offer a preprocessing scheme that enables detection of continuous boundaries for the ABL and other regions of interest. The method adopted here is a two-step filtering approach specially designed to take into account the subtleties of sodar images and their characteristic patterns so that a continuous ABL contour can be obtained. Boundaries of other significant information regions are also demarcated. These contour lines can then be used in determining various features necessary for interpretation of the sodar imageries.