Background and study concerning water wave effects on airborne imagery

Abstract

This paper describes ongoing research and initial results regarding collection of airborne imagery for detection of submerged features in optically shallow water types. The approach is to utilize land surface, water surface and submerged or in-situ line targets of various types during the airborne flights or fixed platforms. The imagery collected by the airborne sensing systems is processed in concept to correct for the presence of the water surface wave effects and water column effects. The correction approach is based upon calculation of a residual image between either (a) the observed submerged target image and the non-submerged image or (2) the observed submerged target within a scene and a synthetic image of the same scene. The residual image thus contains the distortion and blurring effects due to the presence of water waves and the water column. The residual image contains the information needed to scientifically explain in order to improve our scientific understanding of submerged feature recognition. The approach is described can be applied to airborne, fixed platforms, modeled hyperspectral signatures as well as hyperspectral synthetic reflectance imagery of environmental media, features and objects within such media. When applied to hyperspectral airborne imagery of water, the techniques an be used to identify and optimize the bands and channels that can also be utilized in creating filters to be used in traditional, but high spatial resolution mapping cameras for mapping aquatic and coastal environments. Results presented of submerged target imagery demonstrate the ease to detect submerged features on the order of 3 cm 2 using airborne digital data as well as traditional scanned film cameras. The results suggest that gravity wave effects may be removed from low altitude and high spatial and spectral resolution airborne imagery by careful calibration of airborne sensors, especially focal plane focusing calibration and related sensor settings.