Introduction of sensor spectral response into image fusion methods. Application to wavelet-based methods

Usual image fusion methods inject features from a high spatial resolution panchromatic sensor into every low spatial resolution multispectral band trying to preserve spectral signatures and improve spatial resolution to that of the panchromatic sensor. The objective is to obtain the image that would be observed by a sensor with the same spectral response (i.e., spectral sensitivity and quantum efficiency) as the multispectral sensors and the spatial resolution of the panchromatic sensor. But in these methods, features from electromagnetic spectrum regions not covered by multispectral sensors are injected into them, and physical spectral responses of the sensors are not considered during this process. This produces some undesirable effects, such as resolution overinjection images and slightly modified spectral signatures in some features. The authors present a technique which takes into account the physical electromagnetic spectrum responses of sensors during the fusion process, which produces images closer to the image obtained by the ideal sensor than those obtained by usual wavelet-based image fusion methods. This technique is used to define a new wavelet-based image fusion method.

I. Introduction

The existence of a tradeoff between spatial and spectral resolution in remote sensing spaceborne imagery is well known. That is due to a combination of a set of observational constraints imposed by the acquisition system, detector specifications and satellite motion, among others. As a result, spaceborne imagery is usually offered to the community as two separate products: a high-resolution panchromatic (HRP) image and a low-resolution multispectral (LRM) image. In addition, an increasing number of applications, such as feature detection, change monitoring and land cover classification, often demand the highest spatial and spectral resolution for the best accomplishment of their objectives. In response to those needs, image fusion has become a powerful solution providing a single image with simultaneously the multispectral content of the original LRM image and an enhanced spatial resolution.