Sometimes cartographers face difficult problems of type placement that are due to the geography of what we are mapping. For example, the northeastern United States is a densely populated region, and it may be very difficult to label all of the cities that are relevant to a particular map problem because there simply is not enough space on the page. Other problems in placing labels may arise when other map features occupy the space where a label might best be placed. Take the example of a map of China, its major cities and major rivers pictured below. Even in this relatively simple map, it may be difficult to find a satisfactory position for all of the city labels.
If we focus on north central China (see Figure 3.cg.26, below), we can see that there is no good position for Shijiazhuang’s label without creating a conflict with the nearby river. If we move the city’s label to the upper left position, it is still in conflict with the river, while moving it to the upper or lower right creates a conflict with other labels and city symbols. Generally, you will want to avoid conflicts with other map features, such as rivers, roads or other point symbols because conflicts make it difficult for map readers to read the labels. However, in some cases, conflicts may be unavoidable. It is in such cases that we turn to using text effects.
One text effect that is often helpful in situations of conflict between linear map features (e.g., rivers, roads or political boundaries) is using a halo. In the figure below, we have used a white halo to more clearly illustrate what this text effect does: it creates a visual break between the linear feature and the label that makes the type easier to read.
Typically, you will want the halo to be as unobtrusive as possible – a halo with a contrasting color, as in Figure 3.cg.27, above, will be very noticeable, and perhaps distracting, to the map reader. A better solution is to match the halo color to the background of the map behind the label, as in the Figure 3.cg.28, below.
A difficulty you may encounter when you would like to use consistent label characteristics for a particular type of map feature (as we discussed in the Type Characteristics concept gallery item above) but have a changing map background is that the labels may be easy to read in some areas, but difficult to read in others. In the example below, all four cities use the same type characteristics. The label for Jilin is clearly legible against its dark green background. However, the label for Changchung is only partly legible; the portion of the label that falls on the light blue background is very difficult to read. One solution to this problem is to place a slight shadow behind the labels that are difficult to read because of low contrast between the labels and their backgrounds.