MAPS AND CHARTS 



71 



crimination of digits. These include such 

 functions as visual exploration, retention, 

 perceptual judgment, and sometimes mental 

 arithmetic. The above studies indicate, 

 nevertheless, that these media for presenting 

 information yield to experimental evalu- 

 ation. 



Maps and Charts^ 



Maps and charts are ways of representing 

 selected characteristics of regions on plane 

 surfaces. The term "map" is the more in- 

 clusive. "Charts" can be thought of as 

 maps which give quantitative information 

 for technical use, especially in navigation. 

 In contrast to printed text materials which 

 have been extensively investigated, maps 

 and charts constitute an area in which the 

 psychological problems have not even been 

 systematically defined. A tentative classifi- 

 cation of the functions of such instruments 

 from the psychological point of view might 

 be proposed as follows : 



One function is the pictorial representation 

 of an area so that it can be recognized when 

 seen. The engraved coastal charts of the 

 Coast and Geodetic Survey from the period 

 when engraving was in its prime are examples 

 of this type. Certain aeronautical charts, 

 particularly the new experimental flight 

 charts, serve the same purpose. 



The second function is the provision of a 

 symbolic aid for the establishing of a con- 

 ceptual system. The conceptual system 

 often takes the form of a more or less accu- 

 rate mental picture from some imaginary 

 point of view. The typical atlas map show- 

 ing political boundaries presents such a pic- 

 ture in the most direct form. Contour lines, 

 from which one skilled in their use can con- 

 struct a picture of the topography, constitute 

 a more indirect device for the same purpose. 

 It is sometimes necessary to convey a system 

 of relations in three-dimensional space be- 

 tween invisible elements. Wind charts and 

 charts of such undersea conditions as temper- 



* Helpful background references in this field 

 are Deetz (21), Greenwood (25), and Raisz (36). 



ature, currents, and sahnity are examples. 

 To speculate a little, the mental represen- 

 tation may be thought of as being in either 

 visual, verbal, or other terms, depending on 

 the individual. With less tangible phe- 

 nomena such as culture traits the conceptual- 

 ization is less likely to be visual. 



A third function, the distinctive property 

 of charts, is to present data for technical use. 



The same instrument will often serve two 

 or more purposes. Contour lines which give 

 the geologist a conception of the land forma- 

 tion also give the highway engineer quanti- 

 tative data about slope. An aeronautical 

 chart may present a picture of the terrain 

 and also data for navigation by radio. On 

 the other hand, one function may conflict 

 with another. A familiar example is the 

 Mercator projection, whose rectihnear repre- 

 sentation of compass direction is important 

 for navigation, but whose distortion of land 

 area is misleading in political maps. 



The human capacities required in the use 

 of maps would appear to include the more 

 obvious visual discriminations, the ability to 

 interpret several varieties of arbitrary sym- 

 bols, the abihty to structure perceptual fields 

 in particular ways, and perhaps the develop- 

 ment of complex imagery. The intelhgence 

 and education of those using the instruments 

 is often important. Thus, the psychological 

 processes in map reading are much broader 

 than either the analytic discrimination of 

 letters and digits or the stereotyped flow of 

 ordinary reading. 



In some respects the psychological prob- 

 lems that arise in the use of maps and charts 

 are related to the problems of production. 

 In addition to the techniques of printing and 

 typography, such processes are involved as 

 hand- and photoengraving, reproduction in 

 color, the stereographic interpretation of air- 

 plane photographs, and the devising of new 

 systems of projection. Creative as well as 

 technological skiHs are demanded. Such 

 skills are required of penmen in the shading 

 of slopes by short parallel lines of graduated 

 thickness known as hachuring. The task of 



