1. Field of the Invention
The invention relates to a method of detecting geological structures and to obtaining stereoscope views from aerial and satellite photographs. In particular the method of the invention concerns detecting geological structures by viewing either aerial photographs or satellite photographs to produce a stereo or 3D effect and to enhance that effect to enable the structures to be more readily detected.
2. Description of Related Art
Aerial photography and in particular the advent in photo-interpretation occurred in the 1960's. Vertical aerial photography includes imaging in the visible as well as the infra red, radar and microwave bands of the electromagnetic spectrum. Both conventional aerial photographs and infra red photographs have specific applications for the science of geology. Aerial photography is confined to enable study in detail of local areas. For a more extensive study a wider photographic coverage is required. For example the study of sedimentary basins on a regional scale to a continental or national scale requires wider photographic coverage. The need for such regional and national scales of study has led geologists to use Landsat or other satellite photographs at scales from 1:1,000,000 to 1:100,000. The invention is concerned with both aerial and satellite photographs.
It is currently believed that stereovision or three dimensional images cannot be obtained from Landsat data. The current practice is for geologists to view standard processed landsat photographs with the naked eye and observe geological structures such as linears. Linears are structures detected involving meansurements in two dimensions only. The detection of linears from photographs provide limited interpretative value unless the structure is investigated and confirmed by geophysical, geomophological or geological data.
Due to this restricted two dimensional observation of photographs information obtainable in this way has been of limited value.
Vertical aerial photography is well established as a geological mapping tool. Vertical aerial photography not only expedites field mapping but also may reveal information that cannot readily be obtained in any other way. Electromagnetic radiation includes ultraviolet radiation, visible light and infra red radiation (IR). Infra red aerial photography is useful in enhancing the contrast of the terrain and bodies of water are sharply contrasted in relation to land and vegetation types may also be contrasted from one another. Thermal imagery has importance from a geological point of view because differences between various rock types and other aspects can also be distinguished. Geological structures such as faults, fractures, joints, folds, crushed zones and others are detectable because of the relationship of the terrain to the rock type.
Infra red aerial photograph employes a yellow filter over the camera to filter out blue light. However, not all of the blue light is eliminated.
Satellite photography employs a sensor unaided by a filter of any kind and it is possible to record the full spectrum. This is limited by the sensitivity and spectral band of the sensor and the range of physical colour bands available to display the electromagnetic radiation recorded.
The Landsat satellite produces photographs called Landsat masters and these can be obtained in either colour or black and white. The photographs are derived from multi-spectral scanner data (MSS) which comprises radiation in four spectral bands:
Band 4 visible green
Band 5 visible red
Band 6 non-visible infra red
Band 7 non-visible infra red
The colour master is a composite of three spectral bands printed in registery through non-visible infra red, red and green filters on photographic colour negative material. These masters are referred to as "first generation archival masters" and are used to print second generation customer prints or transparencies. The masters are usually at a scale of 1:1,000,000 and cover an area of 185 kilometers square. The picture elements (or pixels) cover an area of approximately 80 square meters.
It is an object of the invention to provide a method of detecting geological structures from aerial and satellite photographs.
It is another object of the invention to provide a method of stereoscopically viewing two photographs.