Hyperspectral Imagery and Terrestrial Laser Scanning Integrated with Surface and Subsurface Data Sets for the Geologic Analysis of the Permian Carbonates of the Khuff Formation - Saudi Arabia
Alhumimidi, Mansour Salem
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An integrated digital mapping and modeling of the surface and surface of the petroliferous carbonates of the Permian Khuff Formation of Saudi Arabia is developed. The 3D digital models of geological outcrops, in their photorealistic form, are textured with color photographs by Lidar generated surfaces as triangular irregular network meshes of the outcrop surface, which is becoming a common concept for geologic mapping and analysis. The optical and physical target resolutions used in the process of acquiring data determine the extent of possible detail in these models. In the identification of rock characteristics, terrestrial hyperspectral imaging is a significant development. The ability to map with a significant number (hundreds) of narrow spectral bands over a range from ultraviolet to thermal with hyperspectral imaging makes the possible detail as indicated by the spectra acquired through spectroradiometers of rock types. This then allows much more detailed discrimination of the characteristics of the rocks than the visible spectrum from standard cameras or the near infrared or visible spectrum available with Lasers used with Lidar mapping. The possibility of automated hyperspectral processing in identifying rock characteristics to determine more subtle variations and boundaries in rocks is explored and tested. Ground Penetrating Radar (GPR) is a high resolution geophysical technique which can map subsurface rock layers up to 20 meters in depth at resolution of 0.5m in this part of Saudi Arabia. The characteristics of the underlying layers, as well as the shape of the rock boundaries are defined. The 3D GPR imaging of the subsurface lithology and stratigraphy adjacent to the road cut is integrated with the models of the photorealistic and hyperspectral images of the exposed Khuff along the road cut, made possible because all the data sets are digital and positioned by global satellite positioning. Programs are developed to link 3D GPR subsurface information with 3D outcrop models with both standard photo textures and hyperspectral textures draped onto 3D models from TLS scanning. This enables the accurate correlation and verification of surface and subsurface geological information. In addition Electrical Resistivity Tomography (ERT) is used in part of the area of the GPR mapping to provide another complementary subsurface data set and modeling. This workflow demonstrates the integration and visualization of surface and subsurface information and models which can be used to interpret the geology, in this case rocks of the petroliferous Khuff carbonates. The existence of such an integrated and visualized data set can be reviewed in the office, and eventually merged with other digital data. The integration and visualization of photorealistic, hyperspectral, TLS, GPR and ERT modeling in a GIS environment facilitates their analyses and the interpretations of the geology.