MAP SYMBOLS: EQUAL-APPEARING INTERVALS FOR PRINTED SCREENS¹

Abstract

common problem in map design is the printing ink. The dot pattern was made as A one of selecting screens with which to dark as possible without having the individual show a scale of values. The screens should, dots coalesce. Figures 1 and 2 show these as closely as possible, give a visual impression screens. commensurate with the values they represent.Some preliminary testing showed that the A typical example would be a rainfall map intervals between the dark tones were too with steps of 10, 20, 40, and 80 inches. How great. To correct this the screens for the tridark should each screen be to give the truest angular-spaced dots from 2 percent to 60 pervisual impression of these values relative to cent were photographically reversed giving each other? The purpose of this study was to additional screens with the following percent determine what values printed screens should values: 40, 45, 50, 55, 60, 64, 68, 72, 75, 78, have to give even-appearing visual steps from SO, 82, 84, 86, 88, 90, 92, 93, 94, 95, 96, 97, white to full color. Tone symbol tests were and 98. All of these screens were printed in made with black, and, in order to see if colored screens behaved the same as black ones, TABLE PE PERCENT VALUES OF SCREENS DRAWN FOR for the colors red, orange, yellow, green, blue, TONE SYMBOL TESTS and brown.2 Tests were also given to see if

Visual features of cartographic representation in map perception

“…It has been found that perception of gray levels does not change depending on whether the tested gray scale covers the shades between the ultimate margins of black and white, or just its subset, and the curves are very similar for all types of raster patterns and colors with the exception of yellow (R.L. Williams 1958).…”

“…Research on the construction of equal value gray scales was conducted by R.L. Williams (1958), A.J. Kimerling (1975) and M.P.…”

Map perception: theories and research in the second half of the twentieth century

“…Eventually though, R.L. Williams (1958) concluded that the curve describing visual perception of value increase is inconsistent with the Fechner's law. As in the case of scaling of the size of graduated symbols, these studies have produced different effects, depending on the experimental method and the structure of the tested areal patterns (raster density).…”

Problems of Cartographic Design in Geographic Information Systems for Transportation

“…Color and area patterns have also been prominent subjects of research on the human factors of map reading. Studies have been done on the perception of gray-scale intervals (Williams 1958), shading patterns (Jenks and Knos 1961), un-classed cross-hatching (Peterson 1979), and the effect "New perception and cognition studies . .…”