Hyperspectral imagery super-resolution

Irmak, Hasan
Hyperspectral (HS) imagery consists of hundred of narrow contiguous bands extending beyond the visible spectrum. It is a three dimensional data cube with two dimensionalspatialinformationandaspectraldimension. Despitehavinghighspectral resolution, HS images have lower spatial resolution due to technological restrictions. ThisdegradestheperformanceinHSimagingapplications. Therefore,increasingthe resolution is a necessity, however the problem is an ill-posed problem. In this thesis, weaddressthisproblem,namelysuper-resolutionreconstruction(SRR)ofHSimages from different perspectives and propose robust solutions. First method proposes a maximum a posteriori (MAP) based SRR technique for HS images when there is only one HS image and no other source of information. The novelty of the method is converting ill-posed SRR problem in spectral domain to a quadratic optimization problem in abundance map domain. Using smoothness prior and inherent properties of abundance maps in the quadratic optimization, a unique solutionisobtained. Moreover,inordertoavoidoversmoothing,apostprocessingis appliedtopreservetexturesintheabundancemaps. Finally,highresolution(HR)HS imageisreconstructedusingtheextractedendmembersandtheenhancedabundances. v Second proposed method is a fusion based SRR method. This method enhances the spatial resolution of HS image by fusing with a coinciding HR RGB or multispectral (MS) image. Again, fusion problem is converted to a quadratic optimization problem in the abundance map domain. Moreover, proposed MAP based approach is also merged into the quadratic equation. That is, this method is a superposition of MAP based and fusion based approaches and closing the gaps of the both methods. Superposition of two methods leads to more robust and efficient SRR method. Similarly, after solving quadratic problem, HR HS image reconstructed from HR abundance maps and endmember signatures. Experiments are implemented on real HS datasets and compared to state-of-the-art alternativemethodsusingdifferentquantitativeimagemetrics. Spectralconsistency,a criticalissueforHSimages,isalsoanalysedintheexperiments. Resultsdemonstrate that proposed methods perform better than competitors based on quantitative metrics while keeping spectral consistency.
Citation Formats
H. Irmak, “Hyperspectral imagery super-resolution,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.