A comparison of user performance on spectral color and grayscale continuous-tone maps

Continuous surfaces such as elevation, precipitation, and temperature are often mapped using isarithms. These representations may be difficult for map readers to understand. Continuous-tone maps are an alternate way of depicting continuous surfaces. Three real surfaces were used to generate continuous-tone maps using spectral color and grayscale color schemes. To assess the effectiveness of these maps, fifty nine subjects were tested. Questions were designed to evaluate how the color scheme affected perception of the surface, and to compare performance on specific map reading tasks. Subjects were shown a grayscale and a spectral color representation of each of the three surfaces. Questions involved the location of surface extremes, elevation estimation, profile identification, landscape position, and interpretation of surface form. Subjects performed significantly better on the spectral color maps than on the grayscale maps.