Scientific attributes and expression methods of geographical boundary

A scientific delineation of geographical boundaries reflects the cognitive level of scientific abstraction and systematic analysis of the spatial variation of geographical objects and is a basic scientific issue of geography. From the perspective of earth system science,this study first explicates the core issues(e.g., basic concepts, scientific contents, and basic properties) of geographical boundaries. Based on the principles of scientificity and systematicness, we then classify geographical boundaries in terms of intrinsic mechanisms, extrinsic appearance and scientific attributes. Furthermore, this paper analyzes the mathematical connotation and representation methods of geographical boundaries, discusses the characteristics of and differences between traditional and modern methods for geographical boundary delineation. Finally, we present a framework for a “geographical boundary model”with an integration of qualitative, quantitative, and positioning methods. Focusing on geographical boundary(a basic theoretical problem in geography), this study engaged in concept definition and method analysis, with the findings enriching the theory and methodology of geographical information science.

THE SIGNIFICANCE OF THE GREAT WALL AS A GEOGRAPHIC BOUNDARY

The Great Wall is not only the symbol of the ancient Chinese culture but also an actual and significant geographic boundary. The arrangements of the wall in past dynasties are based on physiographic conditions, and are just consistent with the demarcation line between semi-humid and arid climates in the country. Therefore,the Great Wall becomes an indicator of the demarcation line between the two areas.The extension and retreat of the wall generally reflect the expansion and shrinkage of farming and animal husbandry areas. From the viewpoint of political geography, the Great Wall can be regarded as the balance belt of 'forces' where the political powers of different nationalities histoncally stood facing each other and had repeated trials of strength. On one hand, the man-made wall of 10,000 li had the function of separating two political units, to some extent, the extension and retreat of the wall reflect the changes of relative strength of the two sides. On the other hand,the conflicts of the advanced and backward forces objectively promoted the economic and cultural exchanges as well as the national assimilation. Today, the Great Wall has lost its function of military works for territorial expansion and defense, but it is still the significant indicator as a geographic boundary and a sensitive area for many geographic elements.