Geoscience Reference
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Figure 4.9 Changing the color reveals extra information. Source of base map: Esri
software.
Select the “show contents of the map” button and change symbols for the
January 2011 high temperatures. Change all of the symbols using “single sym-
bol” to a red circle. Change the July 2011 high temperatures to a red circle
with protruding spikes that looks like a red sun with rays. Change the January
2011 low temperatures to a blue circle, and the July 2011 low temperatures to
a blue sun with rays (Figure 4.9). Can you more easily determine the changes
between January highs and lows in this way? Can you determine the changes
between January and July highs in this way? Does blue convey “cold” or “hot” to
you? Does red convey “cold” or “hot” to you? Why? You should be better able to
distinguish lows from highs, and January from July, with this symbology. Most
often, red is used to convey heat, or “more” of something, while blue is used to
convey “cold” or “less” of something, but this is simply map convention tradi-
tion. These traditions vary around the world and with time. For example, blue
has traditionally been used to symbolize the oceans on European and North
American maps, but green was traditionally used to symbolize the oceans on
maps produced in Asia. If you have time, experiment with other symbology
options, keeping in mind the color theory discussion from this chapter.
Edit the symbology for January 2011 again. This time, instead of “single sym-
bol”, select “color” and vary the color by temperature. Does this help or hinder
your map interpretation? Color can effectively be used to distinguish between
data types and data values. Repeat for the other three map layers. At which
point are there too many color symbol types on the map for you to correctly
interpret it? This is a fine line, and varies depending on such things as the
data user, the data types, and the map scale, but at some point as the number
of colors and symbols increase, the human brain cannot effectively distin-
guish between them. What, in your view, is the ideal color, symbol, and size
to use for each map layer? What, in your view and in keeping with what you
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