Automated generalization in GIS
Wen-Chih Peng · 1997
1. Map generalization has been regarded as an issue of art for many decades; the research efforts on the automation of a generalization process have been gradually transforming this issue into a scientific topic.2. The bottom-up approach in the research of automated generalization attempts to understand the generalization process from the products and experiences of manual generalization, and then simulate the process in a computer.The top-down approach, based on the "theory" of geo-data and GISs, studies first what role generalization should play in a GIS, and in geo-information processing, then investigates problems that may be encountered in playing such a role, and finally, looks for solutions for the problems.This approach is more appropriate than the bottom-up one, for defining the subject of automated generalization.-This thesis3. An automated generalization system is the dream of many cartographers and GIS developers.However, it is important to realize that while database generalization can be fully automated, a view generalization process may need the user -the judge -to participate in decision-making.Thus, interactive-generalization utilities are still required in a GIS, as far as view generalization is concerned.-This thesis 4. To a great extent, view generalization is an issue of competition under certain rules.In the competition, more important or stronger objects "survive", whereas less important or weaker objects have to struggle for "survival" by, for instance, forming "communities" to become stronger (aggregation), or adjusting themselves to adapt to the environment (symbolization, exaggeration, shrinking, typification).Those who fail to do so will be eliminated.In this sense, view generalization can be seen as a process of 'evolution'.-This thesis 5. Being an important property of a map, 'scale' has been used as a critical index for the usage of the map, but it does not have the nature of telling whether the contents of a map of a certain scale were described in the way that best suits a particular application.6.In the context of a GIS, a database should no longer be related to a 'scale' level, but rather, a 'resolution' level, which indicates the level of geometric and thematic detail of the data contained in the database.-This thesis À 7.For many applications in China, data can be obtained in a much more economical and efficient way, by transforming existing detailed geo-databases, if an automated database generalization process is available.8. Conceptual data models are independent of implementation conventions; however, only through an implementation can the promise of a conceptual data model be validated.9. 'Telling the truth' does not always lead to a good effect, and 'not telling the truth' sometimes can be constructive.10.If not being prepared to be a loser, one should not aim to be a winner.11.An irritation at a proper time can be much more helpful than a compliment (after "Proclamatie", Nr. 35, by H. N. Werkman).12. In many instances it is said that 'saying is easier than doing', but generalization is the process for which 'doing is easier than saying'.