Best practices: Modern scale bars are simple and unadorned. In many cases the viewer needs to see only two divisions—one at the beginning and one at the end—and a number indicating the distance between those divisions in real-world units. This is due to the fact that the typical GIS map is not used to measure distances. The scale bar, therefore, serves only to illustrate the general scale of the geographic extent. Subdivisions aren’t needed. The point is, if you are creating a simple map, stick with a simple scale bar. For example, let’s say you are making a 3-inch by 3-inch graphic for a newspaper story that shows general school-district boundaries. You do not need to create a huge scale bar showing 4 major and 4 minor divisions. A single line with labeled end points will suffice. Even with simple scale bars, however, there is utility in providing multiunit scales together on the same map so that the viewer need not perform mental unit conversions should a different unit be desired. Of course, maps that are used for the primary purpose of pinpointing an exact location or distance, such as hiking maps or road maps, do require a more detailed scale bar that shows subdivisions and their associated measurements.
Style: Scale bars are almost always black, or in some instances, dark gray, in color. The font used should conform to the other fonts used on the layout. Several layout styles are possible depending on the space allowed within your layout. The more compact form of the scale bar is used more often on modern maps, whereas the more linear form is a relic from previous decades (see Figure 3.9).
Either format is acceptable, though one should tend toward the compact form since it is more balanced and modern. As mentioned earlier, multiple unit scale bars are sometimes required or beneficial. In this case, we can simply show two separate scale bars with the different units, but place them close enough to one another to maintain an orderly looking layout (see Figure 3.10).
You might also want to note the map scale as a representative fraction (e.g., 1:24000) in the same visual space as the scale bar as in Figure 3.11.
An uncommon way of depicting scale, but still worthy of note if the data is especially suited for it, is to show the scale in area form. Many population density maps, for example, are shown in square mile or square kilometer units and would be ideal for this kind of scale graphic. Additionally, a map with buffers around points at certain distances could also use a scale graphic. See Figure 3.12 for examples. If these types of scales are used, they ought to be shown in conjunction with a conventional scale bar as well.
FIGURE 3.9
Two formats for scale bars are shown here. The compact form is more modern, the linear form is classic.