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Information Visualization (Geographical Data (Types of Information (Region…
Information Visualization
Geographical Data
Spatial Objects
Spatial Extent
Shape
Non-Spatial Objects
Point
Location
Types of Information
Region
Country borders
Location
Latitude, longitude
Identifiers
Names
zipcode, name, etc.
Geocoding
Identifier → Location
Reverse Geocoding
Location → Identifier
Since space is being used to represent actual space, you cannot use space to represent some other quantity.
When the question is inherently spatial
a) Do citi bike commuters tend to drop their bikes in proximity to subway stations? (John Snow's cholera map)
b) How far has the epidemic extended from its point of origin?
When the map helps find information needed (electoral data)
Two Cases against Maps:
Your question does not need a map.
You have a different question.
Advantages
Familiarity
Ask these questions before using a map:
Do I need a map here?
If yes, why?
5 Maps
Dot Map
Heat Map
Hexbin Map
Choropleth Map
Graduated Symbol Map
Dot Map
Density
Distribution
Heat Map
Continuous representation of frequency
Model from data
Density estimation method is required
Information through color
Rainbow has issues:
Different quantities via different colors in rainbow.
Human eye detects intensity much better.
Use perceptually calibrated color ranges
Hexbin Map
Same as heatmap but uses discretized hexagons.
Can be used for categorical information as well.
Choropleth Map
Regions are based on actual geo-political divisions.
Colors to show quantities.
Issues:
Explore appropriate level of details
Skewed distribution → bad visualization
Non-linear mapping of qty to color
Categorical: misleading bc it contains no info for qty
Graduated Symbol Map
Use bubble size for qty
Perception of the region doesn't affect qty
Use color to represent different variables
Use different symbols for another dimension
Put Pie chart at each region to show proportions
Dot Map: objects (Distribution)
Head, Binned Map: density
Choropleth, Symbol Map: values