Automatic Sub-pixel Registration for a Tunable Hyperspectral Imaging System

Hyperspectral imagery of the Earth´s surface is increasingly being acquired from aerial platforms. The many bands acquired by typical hyperspectral instruments are collected either in a push-broom, scanning, or staring fashion. Staring methods can be used in ground and aerial based applications, and have the advantage of readily producing coherent images. Staring remote sensing instruments need some form of co-registration to match band-to-band pixel locations, because it takes some time for the instrument to acquire images and save them as the aerial platform moves above the target scene. A well known method for registration is the phase correlation (PC) which may be used to register images to an accuracy of plusmn1 pixel. In this paper we report an enhancement to the PC method that allows for sub-pixel registration of hyperspectral images. The x-y location at which the maximum correlation function occurs is fitted with a cubic interpolation to find the maximum. This method was implemented to recover sub-pixel rotation and translation accuracy from an airborne hyperspectral imaging instrument, dubbed the portable hyperspectral tunable imaging system. Results showed that the approach improves up to 9.5% of the normalized cross correlation between wavebands in comparison with the PC method alone.