05 0
km mi 5 Sabkha, clay Sandstone Limestone 1 Limestone 2
> Ghazalat lithostructural map. A combination of several bands from the Landsat 7 satellite provided good differentiation of lithology in the arid Ghazalat area. Lithologic discrimination came from one thermal and two SWIR bands; additional image details and colors resulted from the overlay of two visible bands.
The lithology classification was taken from a Landsat 7 Enhanced Thematic Mapper Plus (ETM+) satellite survey over the area. This classification was mapped along with the ASTER DEM data using GIS methodologies. Experience across a broad range of satellite imaging applications has shown that certain combinations of spectral bands discriminate specific types of surface features, and these are often the first ones examined. Although all seven bands can be examined in any combination, it is more convenient to combine three bands to make maps for visual examination. Data from each band are essentially gray-scale data. These gray-scale data can be assigned to one of the three RGB colors, with gray-scale data from two other bands assigned to the other two colors. One common Landsat 7 ETM+ presentation is 742 RGB, in which Band 7 (SWIR) is represented by red, Band 4 (VNIR) by green, and Band 2 (VIS green) by blue.
Sandstone
Marl, loess Limestone
Sandstone
Claypan Limestone Marl, loess, sand Sandstone
05 0
km mi Clay, sabkha
> Ghazalat lithology classification and ground observations. To create this map, geoscientists optimized combinations of satellite bands, independently for each lithology class, including two limestone classes (dark blues), a class encompassing marl, loess and sand (yellow), two sandstone classes (orange), and a class for clay and sabkha (light blue). Mixed colors on this map indicate mixed lithologies within an area. This map was used to plan limited ground traversals, which validated the remotely sensed mapping (photographs, corresponding to circles on map).
5 Sandstone
46
Oilfield Review
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