Читать книгу Change Detection and Image Time Series Analysis 2 - Группа авторов - Страница 24

In this chapter, the problem of the generation of a classification map from an input time series composed of multisensor multiresolution remote sensing images has been discussed. First, the related literature in the area of remote sensing data fusion has been reviewed. Then, an advanced approach based on multiple quad-trees in cascade has been described. It derives from the multisensor generalization of a previous technique focused on the time series of single-sensor data, and addresses the challenging problem of multisensor, multifrequency and multiresolution fusion for classification purposes.

In the framework of this approach, two algorithms have been developed for two different multimodal fusion objectives. In the first one, the general task of jointly classifying a time series of multisensor multiresolution imagery is considered. In the second one, the focus is on the special case of the fusion of multimission data acquired by COSMO-SkyMed, RADARSAT-2 and Pléiades. In the case of both techniques, the fusion task is formalized in the framework of hierarchical probabilistic graphical models – most remarkably hierarchical MRF on cascaded quad-trees. Inference and parameter estimation are addressed through the maximum posterior mode criterion and FMM, respectively.

Examples of experimental results provided by the two proposed algorithms have been shown with regard to high- or very-high-resolution time series associated with case studies in Port-au-Prince, Haiti. The results have suggested that the described algorithms successfully benefit from the data sources in the input multisensor time series, improving the classification result, compared to those obtained using single-mission, single-scale or previous methods in terms of classification accuracy, computation time or spatial regularity.

A major property of the proposed hierarchical Markovian framework is its flexibility. The graphical architecture associated with multiple quad-trees in cascade allows the incorporation of input image sources associated with different sensors, acquisition times and spatial resolutions – jointly. Relevant extensions of this framework may involve the combination with spatial–contextual models within each layer of the quad-trees, or with the intrinsically multiscale structure of CNN (Goodfellow et al. 2016).