Abstract
In order to better constrain the utility of multispectral datasets in the characterization of surface materials, Landsat Thematic Mapper (TM) data were evaluated in the discrimination of geological classes in the Cape Smith Belt of Quebec, a greenstone belt that hosts Early Proterozoic units including those of the Purtuniq ophiolite. Ground-based measurements collected for the study area highlight the importance of chemical alteration in controlling the reflectance properties of key geological classes. The spatial distribution of exposed lithologies in the study area was determined through (1) image classification using a feedforward backpropagation neural network classifier; and (2) generation of fraction images for spectral end members using a linear unmixing algorithm and ground reflectance data. Despite some shortcomings, the database of surface cover generated by the neural network classifier is a useful representation of the spatial distribution of exposed geological materials in the study area, with an overall agreement with ground truth of 87.7%. In contrast, the fraction images generated through unmixing are poor representations of ground truth for several key lithological classes. These results underscore both the considerable utility and marked limitations of Landsat TM data in the mapping of igneous and metamorphic lithologies.
Highlights
Maps of bedrock geology provide information regarding the spatial distribution of lithological units at and near the Earth’s surface, but are typically not precise sources of information regarding the surface distribution of exposed geological materials
The database of surface cover generated for the study area through neural network classification of Thematic Mapper (TM) data (Figure 11) provides surface-cover information that is generally consistent with ground-truth information and complements the information presented in bedrock maps
Chemical alteration is a factor that strongly influences the reflectance properties of several lithological classes exposed in the north-central part of the Cape Smith Belt, Quebec, a region partly underlain by materials of the Purtuniq ophiolite
Summary
Maps of bedrock geology provide information regarding the spatial distribution of lithological units at and near the Earth’s surface, but are typically not precise sources of information regarding the surface distribution of exposed geological materials. Remote sensing techniques increasingly offer a means for the successful discrimination and mapping of exposed rock classes and associated weathering products, providing information that is complementary to that of maps of bedrock geology. The. Landsat Thematic Mapper (TM) series of instruments, though offering modest spectral coverage compared to hyperspectral systems, has retained a central role in the discrimination and mapping of surface cover [3,4]. This study involved evaluation of the utility of Landsat TM multispectral data in the characterization of surface geology in the central part of the Cape Smith Belt of northern Quebec, an. This study sought to (1) characterize the reflectance properties of geological materials in the study area; and (2) determine the utility of Landsat TM data in the discrimination of lithological classes using a per-pixel feedforward backpropagation neural network classifier and a linear unmixing algorithm
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