Three studies to derive rule-based knowledge for automatic map generalization are presented and analyzed. In the tests, cartographers were asked to interpret map objects to be generalized and to describe the basis of their decisions. The studies showed that by interviewing cartographers, much of the domain knowledge can be gathered, but the most time-consuming part of documenting this knowledge is to analyze the data and formalize the results. It was also found that there is important domain knowledge on generalization that has not previously been documented. This paper analyzes the perception of spatial dispersion on point distributions.
Spatial dispersion is one of the major concepts communicated by dot maps.
To promote efficient communication of this concept, two experiments were conducted to investigate the relationship between the perception of spatial dispersion and such map characteristics as spatial arrangement of points, number of points, symbol size, and map scale. Regression models were built on the basis of the experimental results to describe the relationship quantitatively. The obtained models enable map authors to predict the degree of spatial dispersion perceived by map readers. A finite element method was developed to handle conflicts during the generalization of maps. The method is holistic and solves conflict problems for the entire map surface simultaneously.