EMPIRICAL ANALYSES OF DESIGN PRINCIPLES FOR CLASSED AND UNCLASSED POINT SYMBOLS
Key Laboratory of GIS, Ministry of Education, Wuhan University, Wuhan, China
The purpose of this study is to empirically examine the visual search efficiency of classed, unclassed and classed with unclassed point symbols in map environment and provide the design principles for representations with these symbols. Classed and unclassed symbols are often used to represent statistical data set, which has large span. The purpose of classed with unclassed symbol adopted here is to test the effect of visual load with the aesthetic decoration to visual search efficiency. The location and value of symbols on the extreme positions are taken as tasks. The theory of visual search processes is reviewed and some concepts are applied to evaluating the efficiency of the searches according to participants’ response times and accuracy. Results demonstrate some symbol design principals: The units of classed and unclassed point symbols are important factors for visual search; The sketchy marks and the detailed marks should be layered portrayed in symbols in order that the map reader can get the high visual search efficiency while reading maps; Precisely portraying of the small value does not always help to make the accurate value estimating while doing the map-reading task; And, the decoration of the symbol would increase the visual load and become the main factor of decreasing the visual search efficiency.