Benefits of haze removal for modulation-based pansharpening

We show that pansharpening of visible/near-infrared (VNIR) bands takes advantage from a correction of the atmospheric path-radiance term during the fusion process. This holds whenever the fusion mechanism emulates the radiative transfer model ruling the acquisition of the Earth's surface from space, that is, for methods exploiting a contrastbased injection model of spatial details extracted from the panchromatic (Pan) image into the interpolated multispectral (MS) bands. Such methods are high-pass modulation (HPM), Brovey transform (BT), synthetic variable ratio (SVR), UNB pansharp, smoothing filter-based intensity modulation (SFIM) and spectral distortion minimization (SDM). The path radiance should be estimated and subtracted from each band before the product by Pan is accomplished and added back after. Both empirical and model-based estimation techniques of MS path radiances are compared within the framework of optimized SVR and HPM algorithms. Simulations carried out on QuickBird and IKONOS data highlight that the atmospheric correction of MS before fusion is always beneficial, especially on vegetated areas and in terms of spectral quality.