Intro to GIS Exercise #5 – Symbology and Map Layout / Design IUP ...

You have two options for placing dots within an area. Non‐fixed Placement, the default option, indicates
that the dots will be placed randomly each time the map is refreshed, while Fixed Placement freezes the
placement of dots, even if the map is refreshed.
Represent quantity using charts
Bar/Column charts, stacked bar charts, and pie charts can present large amounts of quantitative data in an
eye‐catching fashion. Generally, you'll draw a layer with charts when your layer has a number of related
numeric attributes that you want to compare. Use pie charts when you want to show the relationship of
individual parts to the whole. For example, if you are mapping population by county, you can use a pie
chart to show the percentage of the population by age for each county. Use bar/column charts to show
relative amounts rather than a proportion of a total. Use stacked charts to show relative amounts as well
as the relationship of parts to the whole.
When you symbolize a layer with charts, a chart symbol and a number are placed in the table of contents
under the layer’s name. The number next to the chart symbol represents the attribute value for a chart
symbol of that size on the map. For example, a value of five means a chart on the map that is the same size
as the chart in the table of contents represents 5 data units. Similarly, a chart on the map that is twice as
big as the chart in the table of contents represents 10 data units. The chart symbol and value in the table
of contents also appear in the legend.
For bar/column charts, the value refers to the highest bar in the bar/column chart symbol. With stacked or
pie charts, it refers to the sum of all fields being represented by the stacked or pie chart symbol.
Background Information from the ArcGIS Desktop Help Application
Ways to map quantitative data
Quantitative data is data that describes features in terms of a quantitative value measuring some
magnitude of the feature. Unlike categorical data, whose features are described by a unique attribute
value, such as a name; quantitative data generally describes counts or amounts, ratios, or ranked values.
For example, data representing precipitation, population, and habitat suitability can all be mapped
quantitatively.
Which quantitative value should you map?
Knowing what type of data you have and what you want to show will help you determine what
quantitative value to map. In general, you can follow these guidelines:
� Map counts or amounts if you want to see actual measured values as well as relative magnitude.
Use care when mapping counts, because the values may be influenced by other factors and could
yield a misleading map. For example, when making a map showing the total sales figures of a
product by state, the total sales figure is likely to reflect the differences in population among the
states.
� Map ratios if you want to minimize differences based on the size of areas or number of features in
each area. Ratios are created by dividing two data values. Using ratios is also referred to as