Enhancing spatial resolution of OLI 100m thermal bands through hypersharpening of 30m spectral bands

We propose a two-step spatial enhancement procedure for the two 100 m thermal infra red (TIR) bands of LandSat 8/9, captured by its TIR spectrometer (TIRS), approached as a problem of fusion of heterogeneous data, or multimodal fusion. The fusion algorithm is guided by the statistical similarity between the TIR and visible and near infra red (VNIR) and short wave infra red (SWIR) bands provided at 30 m by the operational land imager (OLI). In the first step, hyper-sharpening is applied from 100 m scale to 30 m scale (3:10 scale ratio): the two TIRS bands are spatially enhanced by means of two linear combination of the 30 m VNIR + SWIR bands, devised to maximize the correlation with each thermal band at its native 100 m scale. In the second step, the thermal bands, previously hyper-sharpened at 30 m, are pansharpened through the 15 m Panchromatic (PAN) band of OLI. The proposed approach is compared to plain 100 m-to-15 m pansharpening carried out uniquely by means of the Pan image of OLI. Both visual evaluations and statistical indexes measuring the radiometric and spatial consistency at the three scales are provided and discussed. The superiority of the two-step approach is undoubtedly highlighted.