maps 3 Flashcards
what is true point data?
True point data: actually measured at
point locations
(e.g. temperatures at weather stations)
what is conceptual point data?
Conceptual point data: collected over areas but conceived of as being located at
points for purposes of symbolization
what are the two groups of proportional symbol mapping?
- Geometric symbols: circles, squares etc
- Pictographic symbols: people, diagrams etc
Bivariate Mapping
Two attributes are combined on the same thematic map/Combination of two colour choropleth maps
Bivariate point symbol maps
Point symbol is used to portray two attributes simultaneously
– e.g. representing two attributes by the width and height of the point symbol
– e.g. representing two attributes by placing a choropleth shade within a point
symbol
Multivariate Mapping
Multivariate Mapping
‘Small multiple’: more than two attributes are shown, each as a separate map
* Difficult to compare two particular points/areas across a set of attributes
* Solution: Combination of multiple attributes on one map
Multivariate Point Symbol Map
Related (or additive) attributes
– Measured in the same units
– Part of a larger whole
– e.g. percentage of various ethnic groups in population
– Can be depicted using pie charts
Chernoff face
distinct facial
characteristics are associated with various attributes
Cartograms
- Distance cartograms:
– Real-world distances are distorted to reflect some attribute, e.g. flight times between major airports - Area cartograms:
– Scale administrative units as a function of the value of an attribute associated with the administrative unit (e.g. population)
Dorling’s cartograms:
Based on a uniformly shaped symbol (typically a circle)
– Size of symbol is function of a variable (e.g. population)
– Algorithm places symbol in centre of each unit; then overlap is gradually eliminated
– Focus is on human geography of a region rather than on its physical extent
– Small areas with large populations are more apparent here than on traditional
maps
– Provide no shape information for administrative units
Worldmapper
- A collaborative mapping project initiated at
the University of Sheffield, led by
geographer Danny Dorling - A collection of world maps available online
- Equal-area cartograms (density-equalising
maps) - Territories are resized on each map
according to the mapped variable - Colours group territories into geographical
regions
Flow Maps
- Show linear movement between places
- Lines are used as symbols to represent flow
– Quantitative: width of flow lines are drawn proportional to the quantity of movement
– Qualitative: lines unscaled and usually of uniform thickness - Arrows indicate directions
Flow Maps: Examples
Traffic Flow Maps
– Show movement of vehicles past a route point
– Varying line widths
– Usually without directional symbols
* Desire Line Maps
– Do not portray actual routes followed
– Illustrate social or economic interaction
– Straight lines connect points of origin and
destination
– Usually without directional symbols
- Example: Multidimensional Scaling
– Multidimensional scaling is an exploratory
technique used to visualise proximities (similarities)
– Data on offices of global service firms in world cities
are used to define service connections between
cities
– Connections are converted into measures of
network proximity
Cyberspace
Cyberspace: ‘navigable space’, from
Greek kyber (to navigate)
* Term originates in William Gibson’s
1984 novel Neuromancer
* Navigable, digital space of networked
computers accessible from computer
consoles
* Cyberspace refers to conceptual
space within ICTs
