How to Make a Thematic Map
Whether you are charting political-party changes or describing population shifts, a thematic map can give your audience an overall view of the issue before you present it in detail. Creating a thematic map, and the kind you create, depends heavily on the data you want to express. Learn to look at data in terms of visual impact. Whether you work by hand or use one of an increasing number of map-software programs, you can learn to make maps that convey a lot of information with clarity.
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Things You'll Need
- Data
- Summary statement of map topic
- Map-making software
- Outline map and graphic supplies
Instructions
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1
Describe the point of your map in a single sentence: "Industrial Growth in Lakeshore County 2000-2010," "Red Counties vs. Blue Counties in 2006 Elections," "Average Household Income 2005 and 2010, by Census Tract in Haven City NY." The information you want to convey will affect the style of your map.
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2
Arrange your data in a grid you can refer to when making your map. Columns in the grid for "Industrial Growth," for example, could show years 2000-2010. Rows could contain the consistent figure you are using to measure industrial growth such as overall dollar amount, number of facilities or number of employees. Further, decide how much of the growth process you want to show. You can easily compare a map for 2000 and a map for 2010 to show that overall industry in Lakeshore County has grown in overall dollar amount. Maps for each year in the grid let viewers trace the growth pattern in greater detail; as you tell them about industrial development in the eastern part of the county, they can see it.
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3
Modify data now, before making the map, if the grid you created is not adequate. For example, a map of Lakeshore County in 2000 and every year after lets you see industrial growth. You could use a color-shaded map to show dollar amounts of growth, although this information will just yield a darker-shaded map for each year. Add information about either kinds of industries or their size, and your map changes style, while becoming clearer and more interesting. Two maps (2000 and 2010) now contain dots showing approximate industry locations. Red dots signify industries generating profits of over $20 million, yellow dots signify $10 to $20 million, green $1 to $10 million, and blue $1 or less. What now emerges is a pattern of small industries in the northeast quarter of the county--a lot of small industries. In one way, creating the map has had an impact on the information you present.
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4
Set limits on what you will present in a thematic map. As shown in Step 3, two or three variables are usually the maximum number to present on a map. Software may adapt to further variables, but it is unlikely that your viewers will. The small industries developing in Lakeshore County may reflect a renaissance, but letting people know the varieties of these industries on the same map as major trends probably will not get your point across. The small industries provide hospital supplies, printing, air filters, computer parts, contact lenses, green cleaning supplies, and recycled lumber; that's enough information to create another map.
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5
Create a map-key from your data. This can mean correlating shades of green with the population numbers they represent, decoding different colors of dots, or explaining symbols. Once a viewer has read your key, ideally he or she can undestand the whole map at a single examination.
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6
Reexamine your data if you find your map extremely difficult to produce or hard to understand. While a map can make information clear, the clarity of the map really depends on the quality of the information; and not the other way round. In situations where changes are small or gradual, for example, a chart may be the most efficient way to convey this information.
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Tips & Warnings
Strongly consider including a thematic map in any presentation where the subject of geography may pertain. Few people carry large amounts of geographic information in memory at all times, and being able to look at even a simple map may expedite discussion beyond the theme of the map.
Symbols can make a thematic map more interesting visually. What bogs down the use of symbols, however, can be called the state-bird syndrome. Seven states (Illinois, Kentucky, Indiana, North Carolina, Ohio, Virginia, and West Virginia) claim the cardinal as state bird. Unless a symbol can help a viewer come to a generalization or conclusion related to the data, it merely constitutes decoration, about which the conclusion is "oh."
References
- Photo Credit Thumbtack in a map image by Nikolay Okhitin from Fotolia.com
