tance placed on black-and-white maps largely may be a reaction to the length of time needed to produce a colored geologic map. In addition to the extra time needed to process the maps, colored maps require extra field time to produce the degree of quality to justify the high cost of colored map printing. Most information portrayed on geophysical and groundwater maps, on the other hand, is accurately and concisely portrayed by black-and-white maps.
Data relevant to the importance of base map elements are given in Table 10 and Figure 6. For geological and geophysical maps, topography, by more than a factor of 2, is considered the most important type of base. Since composite bases include topography, the sum of topographic and composite responses indicates an even greater perceived importance of the topographic base. For groundwater maps, drainage was a close second to the topographic base in importance.
Percentages shown in Table 10 are percentages of the total response to question 6, and reflect the importance map users place on base-map-type combinations relative to other combinations.