Surface-based radar imaging of sea ice

The paper examines the use of a surface-based marine radar for imaging the surface features of sea ice in full ice cover. Two aspects of the problem are considered: 1) selection of radar parameters which maximize the effectiveness of the radar for ice imaging, and 2) evaluation of image processing (display) techniques that effectively convey to an operator the information contained in the radar returns. Both aspects of the study are supported by data collected at a radar site on Baffin Island, Canada. The paper also briefly describes the characteristics of first-year ice, multiyear ice, and icebergs, which are pertinent to the understanding of the radar ice-imaging problem. Based on the results presented on radar parameter evaluation, it is recommended that: 1) the radar resolution should be as high as possible; 2) the antenna should be installed as high as possible; 3) the radar should receive both like- and cross-polarized returns; 4) two radars, operating at widely separate frequencies, should be used. Based on the results of the display work, it is recommended that: 1) the display should use a scan technology that affords the required number of intensity levels; 2) median filtering should be used to reduce the effects of spike noise, if present; 3) normalization should be used to remove the range-dependence of radar returns; 4) selective edge enhancement be employed to maximize significant image detail; 5) to fully utilize the intensity levels available in the display, the histogram of the image should be modified, taking into account the visual response of the operator; 6) color can be used to accommodate the display of multi-parameter images, such as those arising from the use of like. and cross-polarization; 7) Features 3), 4), and 5) may be integrated into a modular image processing system.