Brief introduction of remote sensing geoscience analysis methods
The principles of geological interpretation are: ① from known to unknown, ② from easy to difficult, from the most clearly marked area to fuzzy area, ③ from whole to local, ④ from visual pre-interpretation to other methods, ④ from structural interpretation, and ⑤ from image interpretation to field investigation.
The book Remote Sensing Geoscience Analysis (Chen, 1990) summarizes the main methods of remote sensing geoscience analysis.
(a) Correlation analysis of remote sensing data
In a certain area, various landscape elements are interdependent and mutually restricted. Often the existence of one thing reflects the existence of other things; One phenomenon can indicate the existence of another. In geological interpretation, we can use correlation analysis method to explain according to our understanding of geological laws. For example, Chapter 9 lists examples of polymetallic deposits discovered in Jinchang, Nevada, USA. Through geological research, it is determined that the mineralization in this area is mainly related to endogenous hydrothermal alteration, and the reflection spectrum of hydrothermal altered rocks is different from that of unaltered rocks. Ratio method and other image enhancement processing are used to identify regional alteration, which can be used as an important symbol for finding polymetallic deposits.
(2) Cross analysis method
In order to learn from each other's strengths, remote sensing geoscience research often needs a variety of technical methods to be used alternately. Such as optical image processing, visual interpretation and computer digital image enhancement. When establishing regional typical lithologic stratigraphic interpretation marks, pre-interpretation, field verification, re-interpretation and repeated supplementation and modification are needed to make the established interpretation marks more representative and guide interpretation. When using digital image enhancement processing, the most effective processing method is also selected through preprocessing, on-site object spectral testing and analysis, verification, and then modifying the enhancement processing scheme.
(3) Environmental background method
The so-called background is the regional normal characteristics or normal background values of some geoscience information. Such as the background value of an element in regional geochemistry. For example, the average reflection spectrum value of a certain lithology (such as granite) and so on. These normal features and normal background values obtained by induction, measurement and statistical analysis are normal values. Only on this basis can we distinguish anomalies. Using the anomalies of topography, color, spectrum and some ore-forming elements can guide various geological analysis and research. Therefore, the establishment of environmental background is very important and cautious.
(4) Information synthesis method
Information composition refers to the composition of remote sensing information or remote sensing and non-remote sensing (such as geology) information in the same area. When combined, a new set of spatial information or a new combination into an image is generated through the spatial registration of data and content combinations. The purpose is to highlight useful geological information, reduce and suppress useless information, improve image quality and enhance interpretation and research ability. See chapter 1 1 for details.
(5) Historical comparison method
Historical comparison is to use the time information of remote sensing image data to compare the same area or objects with the same name at different times and make dynamic analysis. For example, the analysis of the development characteristics of the Yellow River and Yangtze River Delta, the analysis of soil erosion in the Loess Plateau of northern Shaanxi, the analysis of the development dynamics of a city, and the analysis of flood disasters (for example, the comparative analysis of 1992 flood SAR images in Taihu Lake area). Summarize development trends and laws from historical comparison to guide planning and governance.
(6) Series drawing method
It is used to represent various geological analysis results in the research area. This is also a very common method in geological work. For example, regional geological survey, regional metallogenic research and geological history and paleogeography analysis are all commonly used methods. Series mapping has three basic conditions: ① it must be based on the same remote sensing information source; (2) there are unified drawing norms and classification principles; ③ Various thematic maps are derived in a certain logical order. For example, in structural interpretation, enhanced remote sensing images are used to compile the interpretation maps of linear and circular structures in the same area. Then the linear structure map and linear structure isodensity map with different strike modes are derived, and the linear structure intersection (fork) isodensity map is derived. The series map of agricultural natural conditions and natural resources in Taiyuan City, Shanxi Province introduced in chapter 12 is an example.
(7) Geographic Information System
It is a computer system for managing spatial data and a technical method developed rapidly by remote sensing in recent ten years. Geographic information system provides auxiliary information for geological remote sensing, which is helpful to the classification and application of geological remote sensing data and improves the quality and speed of geological analysis. Chapter 13 is specially introduced.
(eight) other geological analysis methods.
Some basic analytical methods of geology will also be used in geological interpretation. For example, judging the old and new relationship of faults, dikes and veins according to the intersection relationship, and judging the relative motion of two plates of faults on remote sensing images with structural geology knowledge. I won't introduce them here.