Pitney Bowes MapInfo Professional - Manual (Page 270)

Dot density is particularly useful for showing raw data where one dot represents a large number of
something: population, number of fast food restaurants, number of distributors who carry a brand of
soda, etc.
For example, if you have a table of age demographics broken down into postal codes, you could use
the dot density option to show the concentration of small children in each postal code boundary.
There are three customizing options for dot density maps. You can specify the value of one dot. For
example, you have a table of population statistics, broken down by county. There are 10,000 pre-school
students in Rensselaer County, New York. If you display Rensselaer County according to the number
of pre-school students using the dot density method, each dot could represent 200 students. In that
case, there would be 50 dots in Rensselaer County. You can specify the number of units each dot
represents using the Customize Dot Density Settings dialog box.
When you increase the value each dot represents, you decrease the number of dots that display on the
map. You could modify your dot density map so that one dot represents 400 students. In that case, there
would only be 25 dots in Rensselaer County.
A second option is to change the size of the dots according to your needs, either large or small. If you
are working with large populations, or large counts of something, make the dot size smaller so that the
distribution of dots is easier to see.
Conversely, if your working with a small data set, making the dot size larger might illustrate your analysis
more clearly.
Distribution of dots is random within the region. If you shade states according to population, the
dots for New York are spread out throughout the state; they are not concentrated in New York
City, where the majority of the state's population lives. Note:
Thirdly, in the Customize Dot Density Settings dialog box, change the color of the dot to either red or
black to add more variety to the final map. In this dialog box, you can select Circle or Square dot thematics
and specify the dot density width (in pixels) of the square or circle. In general, squares look clearer at
small sizes. At larger sizes, it may be more appropriate to use circles. You can create multiple dot density
maps on the same layer by varying these options.
MapInfo Professional 12.5 270
Using Thematic Mapping to Analyze Information