Géoinformatique et géostatistique : un aperçu

Visualization of Landsat Image Spectral Space as a Method of Boreal Ecosystems Geomatic Modeling (on the Example of Eastern Fennoscandia)

Litinsky Peter

A new approach to information extraction from Landsat TM/ETM+ imagery is proposed. It involves transformation of image space into a visible 3D form and comparison of positions of the ecosystem signatures in this space with graphical expression of forest and mire cover typology (biogeocenotic scheme). The model is built in the LC1-LC2-MSI axes: the two first principal components of the image matrix in logarithmicm form and moisture stress index. Compared to Tasseled Cap, this transformation is more suitable for the study area. The spectral classes of mature forests line up from the ecological optimum (moraine hills) along two main environmental gradients are : i) lack of water and nutrition (fluvioglacial sandsbedrock) and ii) degree of paludification (lacustrine plains). Thus, the biogeocenotic complexes (Quaternary deposits + vegetation) are identified. The succession trajectories of forest, regeneration through spectral space are also associated with the type of Quaternary deposits. For open mires spectral classes reflect the type of water and mineral nutrition (ombrotrophic or mesotrophic) and the level of water table. The spectral model is a mathematically formalized object that describes the quantitative and qualitative characteristics of the ecosystems. Being deployed in geographical space, it turns into the optimal structural base for integrating the results of discrete field observations into a single space-time continuum. The spectral space model created using measured by the scanner physical characteristics can be the base for objective classification of boreal ecosystems, in which one of the most significant clustering criteria is the position in spectral space.