When you sit down to design your map, one important task is to consider the overall page layout. Particularly in the case of more complicated maps that show multiple views of a place or multiple themes within one page, there may be several good page layout solutions (and often several poor page layout solutions). As your layout design becomes more complex (i.e., contains more elements), it is easy to have difficulty in placing all of the map elements appropriately. For example, in the case of the first map, the cartographer did not place the scale bar carefully enough, and the map reader may be confused about which map frame the scale bar refers to. The scale bar actually refers to the upper map frames. One way of solving this problem might be to place the scale bar within the upper frames. It is important to make sure that map elements that are conceptually related to one another are unambiguously visually associated with each other.
Sometimes, when you are designing multiple frame layouts, it can be challenging to fit all of the map elements in the space you have to work with while maintaining a sense of visual balance (i.e., not crowding map elements on the page). One solution to this problem is to use visual hierarchy (to refresh your memory on this topic, refer back to the Lesson 2 Visual Hierarchy concept gallery item) to ‘create’ extra space, as in the case of the map below, where we allowed the map legend to overlap with one of the map frames.
Marginal elements, like the title, legend, scale bar and north arrow, add important contextual information to a map for the map user. Some of these elements, like the legend and title, can make or break a map. For instance, if a mapped variable is not defined well in the map legend, the map user may not even be able to understand what is visually being communicated in the map. See Figure 3.cg.32, below, for an example of a poor legend.
The above map is of foreclosure rates in August of 2008. But the map legend represents the data so poorly it is difficult to understand which class actually represents the highest foreclosure rates. It is possible that a user of this map would think that the data variable being represented is counts of households filing for foreclosure per county. The cartographer of this map actually is mapping the number of households that filed for foreclosure per the number of properties in the county. To be correct, the classes should read "1 in 10 to 1 in 250", "1 in 251 to 1 in 999", etc.
The map legend explains the data represented on the map. So it is important to spend time making sure the legend itself is as well made as the map. ArcGIS software provides a quick and easy way to create legends, but if all defaults are used, the legend could end up looking poor. Wording, arrangement and alignment should convey a visual hierarchy to a legend's contents. The way the data is represented in the map is the way the data should be represented in a legend. Symbols should not be bigger or smaller in the legend than in the map, nor should they be different transparencies. There are also times where the symbols clearly communicate what they represent and may not need to be in the legend. This is often true if there are not too many symbols and labels to help identify the features. For example, rivers are often symbolized similarly throughout maps, and if labeled as rivers, a symbol for rivers may not be needed in the legend. This leads to times where the legend created in ArcGIS needs editing, or a custom one should be made. Editing legends created through the legend tool can be done by converting it to graphics and ungrouping the graphics. A custom legend or parts of a legend can be made manually with text and graphics or by converting symbols to graphics and copying and pasting them into the legend.
A north arrow is most useful on large-scale maps when direction cannot be inferred from the geographic information. North arrows should not be used on maps at very small scales where the direction of North varies substantially.
A north arrow placed on the above map would be incorrect for much of the map since the direction of north changes from left to right. For instance, in some parts of Alaska, a north arrow would point about 45 degrees clockwise from the top, but in Maine, north would be a few degrees counter clockwise. For small scale maps like this one, longitude and latitude lines are best used to indicate direction.
Map scale can be communicated three different ways on a map: graphically, as a representative fraction, or stated textually. The graphic method (e.g. a scale bar) is the most functional as it will remain correct in reproduction and when a map is viewed digitally. Representative fractions and statements (e.g. one inch equals 10 miles) may be incorrect when a map is reproduced at a different size than the original or viewed digitally due to screen resolution and zooming.
Depending on the map projection used, it is possible that the map scale can vary across a map. If the map scale varies enough, it may be wise to not communicate scale on the map, or qualify the scale by stating at what place(s) the scale bar is correct (e.g. along a certain latitude).
If using scale bars to communicate map scale, they should use well-rounded numbers, e.g. 1, 5, 10, 1000, etc, that can easily be used by the map reader. For many thematic maps where distance is not of main concern, a very basic scale bar can be used. See Figure 3.cg.34, below.