Image and Graphics Processing of Computer-Aided Cartographic using Remote Sensing data
Wang Weimin,Cui Weihong
Institute of Remote Sensing Application
Chinese Academy of Sciences
P.O. Box 775, Beijing 100101,P.R. China
Abstract:
To realize automatic extraction and mapping of remote sensing information, it’s an important technical means that adapt the development of remote sensing technology system and speed up the remote sensing application .
This paper introduces how to use the technical method of computer classification and automatic mapping to make the thematic map of land use; then describes the test and choice of the composite about different types of remote sensing data and the method of classifying types, the constructing method of polygons boundary; finally, discusses the features of the methods .
The methods are achieved on the Microcomputer Image and Graphics Processing System .
The research on remote sensing, cartography and Geographic Information System (GIS) we are engaged in is right within the category of information sciences. Remote sensing is a source of global information, map is a carrier of spatial information and GIS relates them to each the to form information flow and have the capacity for storing, retrieving, analyzing and quick displaying the information flow and supporting decision making. Therefore, we should strengthen the connection and coordination among them and shape an overall iaea of the integrated discipline system to enable this spatial science to benefit our economy and society more.
The emphasis of this paper is to discuss several methods of image and graphics processing in Remote Sensing thematic cartography . Image processing and graphics are two important steps in R.S information automatic cartography . The former, by which thematic information is obtained, is the basis for quality of map compilation, while the latter is, according to determined objective and fixed rules, form new information combination by careful sieving, technology and analytical processing. Obviously, there is a little difference between them both on definition and on denotation. However, with the emergence of digital image and digital map, it’s possible, by the medium of computer and digital techniques, to realize conversion and mutual-supplement of image and graphics data. So, from our point of view , the critical problem in Remote Sensing automatic cartography is the data processing techniques, in which the conversion between raster and vector data, patterns is the key problem. Expert System method and Intelligent Theory is very useful for the solution of data conversion.
1. Study of image processing methods .
The application’s potentiality of Remote Sensing images depend not only on the properties and qualities of images but also on the methods used in image processing. Because the classification and extraction of R.S image thematic information has a close relation to the distinction of object boundary, contour enhancement plays a great role in image processing. There are several methods that we can use to carry out contour enhancement processing, but the results of these methods are not satisfactory, because the noises also enhance with processing. Here , we improve the parameter high pass filter and obtained satisfactory results. The equation is as following :
G(I,j)=P(I,j)+f(Dp)+(A-P(I,j)(1-B)
Where: P(I,j) is the grey value of the central pixel in the chosen window;
F(Dp) is function of contour enhancement;
A is additional offset to high pass filter;
B is a constant, ranging from 0.0-0.1;
Dp=P(I,j)-M(I,j);
M(I,j) is the mean grey value of the window in which (I,j) is the central pixel. The value of Dp changes with the boundary areas than in inside areas; Function F(dp) can be determined according as the boundary as sharp, medium-sharp or smooth. So, image processing can be optimized by several ways of contour enhancement.
