Abstract: This paper discusses techniques for overcoming two problems associated with detecting and classifying small targets in tropical environments on hot sunny days. The first problem is associated with ground-based thermal imaging through a turbulent atmosphere, rising up from the sunlit hot ground. Of interest are ways of reducing the level of apparent shape distortion and motion, and blurred edges in thermal imaging. The second problem is the daytime detection of targets in cluttered sunlit woodland. Targets dwelling in the shadows are obscured in scenes dominated by the sunlit foliage and sunlit ground. A method of filtered thermal imaging suppresses the sunlit and sun-heated features and provides a means of detecting thermal signatures of shaded objects.