Feature symbology greatly
affects how readers interpret a map. The right symbols can mean the
difference between confusion and clarity—between conveying a little
information or a lot. The right symbols can also reveal patterns in your
data that may not be obvious. Listed below are key points you should
remember about symbolizing maps.
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Point, line, and polygon
symbols have properties that you can set, such as shape, size,
color, outline, and width.
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Effective symbols take
advantage of common associations that people make, such as blue for
water or a larger dot for a more populated city.
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Symbolizing features by
attributes allows you to communicate more information.
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You can symbolize
features to show categories (names, types, ranks) or quantities
(counts, amounts, rates, measurements).
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Quantity attributes can
be classified using different methods, including natural breaks (the
default), quantile, equal interval, and manual. |
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Which classification
scheme you choose depends on the purpose of the map and the
characteristics of the data—there is no one "correct" choice. |
Review questions
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When you label map
features in ArcMap, where does the text come from?
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When classifying a layer,
what rule of thumb can you use to decide how many classes to use?
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Name two things you can
learn from a classification histogram.
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Name two ways that
density can be symbolized on a map.
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In ArcMap, label
text comes from a feature attribute or you can manually add
your own text to a map.
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When classifying
data, fewer classes is generally better.
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You can learn
many things from a classification histogram. Your answer
could have been any of the following:
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How attribute
values are distributed across the whole range of values
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The minimum
attribute value
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The maximum
attribute value
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The number of
classes
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The class
breaks (maximum value for each class)
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The size of
classes relative to one another
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The number of
features that have a particular attribute value. |
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You can show
density on a map by normalizing an attribute by area and
using graduated color or graduated size symbols; you can
also create a dot density map.
Key terms