Lettering
Type taxonomy
A map reader sees letters as visual stimuli and reads letters as verbal mental representations at the same time.
Devise a taxonomy that uses the visual variables of typefaces to distinguish and associate the different things that appear on the map. First, make a list of the kinds of things that appear on your map. Draw out a tree that identifies kinds of things and then sub-kinds of those kinds, if necessary. Then use a different type style to distinguish each kind of thing. Add subtle differences to distiinguish different sub-kinds. You can use hue, size, capitalization, bold/italic and fonts (Garamond, Helvetica, etc) to develop your type taxonomy.
Visual association
Symbols with labels generally involve two or more kinds of signs that are supposed to be working together (i.e., a geometric shape conveys location and a text label conveys attribute).
Help the reader associate symbols from two different systems (verbal and visual) by associating the visual variables of each. For example, use the same hue to associate line and label and balance the weights of lines and fills used in two or more systems.
Rights of way
You often add labels to places on a map after you have drawn other symbols (points, lines, and regions), but if you write labels directly over these geometric features, you will make it difficult to read the labels.
Labels should have right of way over other features, especially line features. Knock-out line features that lie directly under a label so that the line of the symbol and the line of the letter do not touch. Make sure that any fills that lie directly under a label do not reduce the contrast of the label and make sure the contrast is consistent across the map if the labels lie over fills of different tones and hues.
Imhof’s position
Classically trained cartographers have been taught rules for positioning names on maps that are based on principles. You should know these principles, when you should follow them, and when you can break them.
Eduard Imhof worked out many rules of thumb to guide how labels should be positioned on maps in “Positioning Names on Maps.” Always have a copy of this paper with you and refer to it when you make decisions about how to put text on your map. The rules are useful and most other classically trained cartographers will be aware of them (and will thus notice if your map does not adhere to them).
Between but not touching
People can read labels even if the letters of one label appear between the letters of another, but will be distracted if the letters of different labels touch.
Employ a consistent text hierarchy using size and shape variables. No characters should overlap or touch any other characters, but some labels of one type may appear between characters of another, larger type.
Put labels in place
A map with a lot of different kinds of features that are difficult to represent iconically or through convention will need to define the symbols so that the reader can learn the symbol system. Legends can be cumbersome for readers, however, because they split the readers attention and carry a higher cognitive load.
For nominal features or descriptive qualities, put labels directly on the map at the location of that feature or with that quality. Be judicious, but when a feature or quality is important, then tell the reader directly. For example, if the purpose of your map is to help boaters navigate a coast, then label the places on the coast that are rocky or shallow.
Look of time and theme
The look of type connotes a cultural context for a place, time, and theme.
Choose a typeface that relates to the map’s theme, geography, or historical context.