A High Dynamic Range Sonar and Radar Image Rendering with Glow Effect to Help Image Interpretation

We present a novel visualization scheme for high dynamic range imaging data (typically sonar or radar), which makes it possible to visualize and assess the strength of high amplitude echoes while not preventing the visibility of shadows. The approach uses a dual tone mapping where low amplitude data is represented using a value scale with an essentially constant hue and saturation, and the high amplitude data is represented using a hue scale with a constant value and saturation. Moreover, the visibility of strong echoes is enhanced thanks to a non-linear low pass filtering, creating the effect of a halo or glow around strong echoes, emulating the effect of old cathode ray tubes which was often used by sonar operators to interpret the images and which was lost with modern screens until now. The paper presents results of our method on actual data acquired by a high-end synthetic aperture sonar system.