Geog. 370 Lecture 9

Front 1

Dot density map

Back 1

dot density map (again): a thematic map in which the density of dots within enumeration units or grid cells are scaled in proportion to the attribute values associated with the units
appropriate for mapping discrete phenomena that change smoothly
dot density maps primarily use the visual variable arrangement to represent attribute information
the term numerousness perhaps is more appropriate: the combination of the layout and number of graphic marks constituting a sign vehicle

Front 2

One to one dot maps

Back 2

one-to-one dot maps: each dot on the map corresponds to a single entity of the overall mapped phenomenon
represent individual level data
qualitative point symbol map: maps that use highly #Iconic symbols to reference point features accurately

Front 3

One to many dot maps

Back 3

one-to-many dot maps: each dot on the map corresponds to a pre-determined number of incidents of the mapped phenomenon #DotValue
also: dot density map, dot distribution map
represent enumerated information that is not normalized

Front 4

Design Considerations for Dot density maps

Back 4

our perception of arrangement/numerousness is poor
-makes dot density a poor option for uniformly distributed attributes

Front 5

Dot value

Back 5

1. dot value: the number of entities of the represented geographic phenomenon that each dot represents
too large: there won't be enough dots to show nuances in the distribution
too small: the map will be covered in dots
use rounded, meaningful numbers

Front 6

Dot size

Back 6

2. dot size: the amount of space taken up by a single dot on the map page
too small: you dots won't emerge to the figure
too large: dots will coalesce
rule of thumb: dots should begin to coalesce in enumeration units with the highest rates and there should still be 2-3 dots in enumeration units with the lowest rates
rule of thumb: communicate dot value and dot size through a visual legend
-Include a verbal statement (one dot equals .....)

Front 7

Enumeration units

Back 7

3. #EnumerationUnits: the basemap geography to which the geographic phenomenon is aggregated
o should be meaningful to the distribution of the geographic phenomenon
Information does not need to be normalized
Projection must be equivalent

Front 8

Dot placement

Back 8

4. dot placement: how each dot is placed relative to the entities it represents
randomly place dots inside of the enumeration unit
Use ancillary mapping information (dasymetric mapping)

Front 9

Dot density controversy

Back 9

2010 Census
dot density maps are most appropriate thematic map type for mapping the distribution of humans (i.e., population)

Front 10

Dasymetric map

Back 10

dasymetric map (again): a thematic map that leverages ancillary information to exclude areas that do not contain the mapped phenomenon
use when the enumeration units are not meaningful to the geographic phenomenon