Identification of lineaments using Google tools

摘要

Recent advances in data acquisition technologies, have led to a growing interest in capturing high resolution rock surface images, Digital geologic maps that use a virtual globe interface, like google earth are a relatively new medium for presenting geologic data and interpretations. Models viewed in google earth are more intuitive for visualizing 3-D geological structures than traditional paper maps. Google earth displays satellite images of varying resolution of the earth's surface, allowing us to see things looking perpendicularly down or at an oblique angle, with perspective. Geological lineaments represent the intersection between discontinuity planes and an observation surface. Lineament identification plays key role in an underground project in all phases of the investigations and construction stages. Lineaments perceived in google earth images are reliable indicators of geologic structure. For identification of lineaments, google earth images technique is the most effective tool in conjunction with ground truth and top sheet for collection of spatial information and very useful in identification and mapping of the lineaments of an area. Structural geology studies, geologic lineaments and their pattern information are essential for better planning and timely execution of projects to avoid any hazards, google earth images provide lineament information. The present work deals with the integration of satellite imagery and surface geological data to improve the structural knowledge of any project. In this paper outline a methodology that allows efficient mapping for identification of geologic features and lineaments using google earth image of the rock surface in various phases of a project. In this paper also provides techniques to generate and display 2D and 3D geological data in google earth, oriented 2D and 3D geological symbols based on outcrop data and contour creation are covered. CAD Software such as SketchUp is used to generate the structural symbols for mapping ground based structures in google earth and to convert graphic images files of 2D into 3D Collada object models that are capable of being stretched, oriented and rotated in google earth for display in profile view. Excel worksheets are used to generate KML scripts for the structural symbology and well field visualization. A interactive google earth geologic map was built in various stages of an underground project, this technique described with a case study, this covers the use of google earth tools in different stages of a project, in pre-investigation/desk study stage identify the lineaments using google earth and find out the outcrop & co- ordinates for surface mapping and generate contour map using SketchUp. During detail investigation stage, assign joint orientation in google earth and developed a predictive lineament trend map to better interpretation of the geologic features for construction. During construction stage, back analysis this predictive lineament trend map with actual structural geological map of the project then predicted lineament trend map (generated using google earth tools) are compared against actual structural geological map & structural map can be optimised for further excavation. This map was produced in very short time, this shows the potential of using this method for predicted and efficient mapping of geological structures, particularly from remote, inaccessible or hazardous sites. Further an attempt has been made for mapping of lineaments and knowledge base preparation using google earth techniques for part of the proposed project site. Categorized the identified lineaments and geologic structures as per their features and projected these features for future projection nearby. This methodology might potentially be adopted for the identification of several features of geological origin. Applications such as identifying suitable site for dams, reservoirs and underground structure facility, and finding potential risks associated