The Role of Symbol Form and Legend Design in Proportional Point Symbolised Maps: An Experimental Study in Thematic Map Design

Abstract

Point symbols are the most commonly used proportional symbols in thematic mapping. Traditionally two types of symbols have been in use in this category -proportional squares and circles. These studies have reported malfunctioning of these symbol forms in terms of the errors reflected in response outputs of the magnitudes both in absolute and relative modes when these are read from the symbols placed in map environments. This malfunctioning of the symbol among other factors was ascribed to the type and design of symbol form and the legend provided on these maps. This paper examines the deficiencies in symbol form design of proportional circles and squares together with the existing design practices of legend design. An effort will also be made to improve symbol form by (1) adding (a) uniform gray area fills (b) graded gray area fills in the open circle and square form together with (2) an improvement in legend deign and its organisation. These design improvements will be tested experimentally by measuring the resulting improvements in terms of both efficiency and effectiveness of visual information processing. The experimental results have shown enhancements in both efficiency and effectiveness in information processing from maps due to proposed design improvement.