Learning Map Composition
Cartography and map composition may seem like an entirely new discipline to many GIS and image processing analysts—and that is partly true. But, by learning the basics of map design, the results of your analyses can be communicated much more effectively. Map composition is also much easier than in the past when maps were hand drawn. Many GIS analysts may already know more about cartography than they realize, simply because they have access to map-making software. Perhaps the first maps you made were imitations of existing maps, but that is how we learn. This chapter is certainly not a textbook on cartography; it is merely an overview of some of the issues involved in creating cartographically-correct products.
Plan the Map
After your analysis is complete, you can begin map composition. The first step in creating a map is to plan its contents and layout. The following questions may aid in the planning process:
- How is this map going to be used?
- Will the map have a single theme or many?
- Is this a single map, or is it part of a series of similar maps?
- Who is the intended audience? What is the level of their knowledge about the subject matter?
- Will it remain in digital form and be viewed on the computer screen or will it be printed?
- If it is going to be printed, how big will it be? Will it be printed in color or black and white?
- Are there map guidelines already set up by your organization?
The answers to these questions can help to determine the type of information that must go into the composition and the layout of that information. For example, suppose you are going to do a series of maps about global deforestation for presentation to Congress, and you are going to print these maps in color on an inkjet printer. This scenario might lead to the following conclusions:
- A format (layout) should be developed for the series, so that all the maps produced have the same style.
- The colors used should be chosen carefully, since the maps are printed in color.
- Political boundaries might need to be included, since they influence the types of actions that can be taken in each deforested area.
- The typeface size and style to be used for titles, captions, and labels have to be larger than for maps printed on 8.5" × 11.0" sheets. The type styles selected should be the same for all maps.
- Select symbols that are widely recognized, and make sure they are all explained in a legend.
- Cultural features (roads, urban centers, and so forth) may be added for locational reference.
- Include a statement about the accuracy of each map, since these maps may be used in very high-level decisions.
Once this information is in hand, you can actually begin sketching the look of the map on a sheet of paper. It is helpful for you to know how you want the map to look before starting ERDAS IMAGINE. Doing so ensures that all of the necessary data layers are available, and makes the composition phase go quickly.
See Map Making workflows for instructions on creating a map. See Help for details about how Map View and the drawing and layout tools work.