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Cartography: Symbolic representation

Point symbol are scaled in proportion to the magnitude of data occurring at point locations,
such as using circles of varying size to represent city population

Two forms of point data
- True Point Data: actually measured at point locations (e
...
Temperature at weather
station)
- Conceptual Point Data: collected over areas but conceived of as being located at
points for purposes of symbolisation
- Intermediate forms e
...
data on cities

Two Groups of proportional symbol:
- Geometric symbols: circles, squares etc
...
g
...

John Snow’s 1854 Cholera Map

Dot Mapping
- Portray raw-total data (e
...
The number of students living in wards in Loughborough)
- Each dot equals a specific value (e
...
1 dot = 100 students)

Dot Size And unit values
• Dot Sizes:
- Too Small: distribution appear space and insignificant
- Too Large: impression of excessive density
• Dots in the densest area began to coalesce
• Unit Value: the count represented by each dot on a dot map

Comparing Thematic Maps
- Comparison of two attributes for a single point in time
- Comparison of the same attribute over two time period
- Comparison of same type of thematic map
- Comparison of two Different types of Thematic maps

Bivariate Mappings
• Two attribute are combined on the same thematic map
Bivariate Chloropleth Maps
- Combination of 2 colour Chloropleth maps
- Information about regions of homogeneous values combinations
- Clear legend
Bivariate point Symbol Maps
- Point Symbols is used to portray two attributes simultaneously
- E
...
Representing 2 attributes by the width and heights of the point symbols
- E
...
Representing 2 attributes by placing a choropleth shade within a point symbols
Combined Choropleth and Proportional Symbol Map
- Size of proportional symbol: raw-total data
- Choropleth: standardised data (rate)

Multivariate Mapping
- Small Multiple = more than 2 attributes are shows each on a separate map
- Difficult to compare 2 particular points/areas across a set of attribute
- Solution: Combination of multiple attributes on one map
Multivariate Point Symbol Map
Related (or ADDICTIVE) Attributes
- Measured in the same units
- Part of a larger whole
- E
...
Percentage of various ethnic groups in population
- Can depicted
NON RELATED (NON ADDICTIVE) Attribute
- Measured in dis similar units
- Not part of a larger whole
- E
...
Percent urban and median income
- Different multivariate points symbols available e
...
Chernoff Face: Distinct facial
characteristics are associated with various attributes

COMPUTER CARTOGRAPHY


1950 and 1960s: QUANTITIVE REVOLUTION in geography
- Geography as ‘spatial science’
- Analysis of spatial patterns and geometries
- Increasing use of computers
- Waldo Tobler (1959) ‘Automation and Cartography’ in Geographical Review- early
programmatic paper
Computer-Assisted mapping developing in 1960s:
- Reducing costs of map production
- Shortening the time of map creation
- Dealing with large quantities of data
- Producing maps of the same quality
Several Generations of Computers Mapping
- Output on line printer
- Output on line plotter
- Output on mainframe computer screen
- Desktop mapping on PC (mid 1980s)
- Web maps and multimedia (mid 1990s)
Major Developments
- Increasing quality
- Increasing flexibility
- More than producer- centric to user- centric map creation
- Integration of desktop mapping and GIS

GIS: Geographical Information Systems
GIS is an organised collection of computer hardware, software and geographic data
designed to efficiently capture, store, update, manipulate and display all forms of
geographically referenced information’- Dangermond:1992
• Combines the functionality of a conventional database management system (DBMS)
with the functionality of a computer mapping programme
...

- Animations
- Virtual landscapes

GIS: Geographical information Systems
Four important components of a GIS (Robinson et al: 1995)
- Hardware
- Software
- People or ‘Liveware’
- Data

Digital Foundation
Hardware:
- Computer platform (PC, mainframe)
- Standard input and output devices (keyboard, mouse, visual display unit)
- Storage media
- Specialist peripherals for input (scanners and digitisers) and output (plotters,
printers)
Software
- Several comprehensive packages available
- For use in practicals: ArcGIS10
- By ESRI (Environmental Systems Research Institute): founded in 1969, 1982
ARC/INFO 2010 ArcGIS10; leading suppliers of GIS software
Data
- Expensive to collect, store and manipulate (large volumes_
- Collected by numerous agencies through remote sensing, aerial photography,
national mapping programmes
- Available in analogue form (paper format) and digital formats
- Data quality crucial: reliability, precision, accuracy, completeness, consistency
- Two types:attribute and spatial data
People or Liveware
- People responsible for designing, implementing and operating a GIS
- GIS and cartographic training important
- Map user

GIS: Example
- Water utilities
- City Councils
- Telecommunications company
- Super market
- Ecologist

SPATIAL DATA: CAPTURE, CODING and CATEGORISATION

Spatial Data
• Spatial (geometric) data
• Where a feature is
• Refers to location and dimension
• Co-ordinate based
• 2 methods of representing geographic data digitally
- Vector Data

- Raster Data

Raster Data
• Representation of the world as a surface divided into a regular grid of (usually square
cells)
• Properties (attributes) are assigned to cells
• Cells are called PIXELS: picture element
• Varying spatial resolution (length of a cell side as measured on the ground)- higher
resolution, the smaller the pixels
• Each cell is given a single valve
• Detail about variation within cells is lost
• Useful for storing data that varies continuously (e
...
Aerial photographs, satellite
images, elevation surface))
• Methods of capturing raster data:
- Remote-sensing satellites
- Scanning

Scanning
Working principle of a scanner
- Map is scanned in narrow continuous bands
- Sensor registers light intensity or colour value of small square
- Measurements are transformed into digital values
- Reconstitution of original colours
(Kraak and Ormeling: 2003)

Sources for Raster Data
• National Mapping Organisations
• National and Regional government agencies
• National data centre e
...
EDINA (ordnance Survey Map)
• Commercial and military providers of satellite images
• Other public and private geographic data providers

Vector Data
- Raster is Faster BUT Vector is Corrector
- Useful for storing data that have discrete boundaries (e
...
Country data, land parcels,
streets)
- Method of capturing vector data: Digitalising

Digitalising
• Converting analogue into digital vector data
• Heads-up digitising:
- Combination of scanning and digitising
- Map is scanned first and displayed ad enlarged on monitor
- Follow/trace and enter with the cursor the relevant lines or point locations on the
screen

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BUT: use existing boundary files if possible (often commercially available e
...
Digital
geometric descriptions of administrative units)


Sources for Vector Data
• National mapping agencies (e
...
Ordnance Survey)
• National and regional government agencies
• National data centres e
...
UK Data Service Census Supports (provides boundary data
through the boundary data selector facility)
• Other public and private geographic data providers

Raster vs
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g
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g
...
g
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Digital Map


From Computer Cartography to GIS

Volunteered Geographic Information
• Widespread engagement of large number of private citizen
• Democratisation of GIS
• Web 2
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g
...

• Large scale: TOPOGRAPHIC MAPS
• Small scale: maps of states or continents in atlases

Thematic Maps
• Special purpose maps
• Concentrate on the distribution of a single attribute or the relationship among
several
• Portray the variation within a class of feature
• E
...
Maps of election results, average annual income precipitation
...
)
• Disease distribution (e
...
Cholera)
• Population densities
• Production and movement of goods (first floe maps in late 1930s)
• Related to emergence of large scale collection of social statistics (e
...
Census)

Moral Geographies: Maps of moral statistics
• Charles Dupin’s first map of moral statistics
• First known choropleth

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Education content: number of persons per male child at school
Influential example
Charles Booth’s Poverty Map of London 1896


Choropleth Maps
A map in which numeration units (or data collection units) are shaded with an intensity
proportional to the data values associated with those units (e
...
Census tracts shaded with
grey tones with an intensive that is proportional to population density
• Suitable option for a particular data set
- if spatial variation of observed phenomenon varies with administrative unit
- Similar size and shape of administrative units
• Standardise data to account for differing sizes
- divide 2 area – based raw totals (e
...
Number of divorced/number of married)
- Calculate a rate (e
...
Number of suicide per 100,000)
- Calculate a summary numerical measure (e
...
Median)
• Select number of classes and method of classification
- Consider the distribution of the data
- Consider the level of precision of final map
- Consider ease of understanding
Choose a colour scheme
Design a readable legend
Add other map element

Data Classification: Number of Classes
• Statistical information is generalised to search for spatial patterns
• Data are allocated to a member of classes
• Too few classes:
- Little variation, no clear patterns
- Data distribution not adequately reflected
• Too many classes: difficult to differentiate
• Max number depends on:
- Data distribution
- Use of grey tones (less) or more (colours)

Data Classification: Method
• Decide on classification method to determine class limit
• Depends on the nature (distribution) of your data
• Depends on the purple of the map
• Choice of classification method determined appearance (and message) of map
• ArcMap offers 7 classification methods for making a graduated colour map

Natural Breaks
• ArcMap default
• Looks for groupings in the data
- minimises variation within each class
- Identifies ‘big jumps’ in the values

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Values within a class are likely to be similar
Good for data that are nit evenly distributed
Difficult to compare different maps
Difficult to choice appropriate number of class


Quantile
• Equal number of observations in each class
• Good for evenly distributed data
• Emphasises the relation position e
...
Which counties are in the top 20%)
• BUT: Features with similar values may end up in different class especially if values
cluster
• Few wide ranging adjacent values may end up in the same class

Equal Interval
• Each class has an equal range of values
• The difference between the high and low value is the same for each class
• Easy to interpret
• Good for mapping continuous data; no gaps or missing values in classification
• Good for comparison of a series of maps
• Inappropriate if values are clustered: there maybe many features in 1 or 2 classes
and some classes with no feature

Standard Deviation
• Each class is defined by its distance from the mean value of all feature
• Good for displaying features above or below an average valve
• Good when the distribution is normal
• BUT: Does not show actual values of features, only their distance from the mean
• Very high or low valves can show the mean so that most features will fall into the
same class

Unique (Manual)
• Class boundaries set in accordance with external criteria
• E
...
State requirements; specific criteria set by researcher
• Require an understanding of the broader context of the data


A Brief History of Cartography

Cartography- discipline dealing with the conception production, dissemination and study of
maps in all forms

Traditional approaches to its history
(Dorling and Fairbairn: 1997)
- Darwinian view: Map making improves as civilisation progresses- focus on accuracy
and technology
...

250 BC – Eratosthenes produced map using a grid to locate position
First to calculate the circumference of the earth

Ptolemy’s Geographia
• Key cartographic thinker
• Devised system of longitude and latitude in 2nd century AD
• Translation of his work influenced European Cartographies in 15th century

Medieval European Cartography (400 AD – 1450 AD)
• T-and-O mappae mundi
• Medieval European representation of the world
• From early 7th century
• Point East to paradise
• In early Christian interpretation, Europe thrid continent that Noah distributed among
his son

T- and –O Mappae Mundi
• City of Jerusalem often depicted as centre of the world
• Here: Jerusalem and Rome mapped as part of Europe (a) tripartite (b) quadripartite
(c) zonal (d) transitional

Medieval (European) Maps
Dorling and Fairbairn (1997) suggests 4 phases:
• AD 400 to AD 700: little cartographic output
• AD 700 to AD 1100: Monastic institutions dominate; religious influences stronger
• AD 1100 to AD 1300: Crusades and pilgrimages; maps of the holy land
• AD 1300 to AD 1450: transition period; re-emergence of Pltolematic coordinate
system; navigational chart (Portland)

Renaissance Maps
• Age of Discovery (from AD 1450)
• Portuguese navigators: African coast: sea route to India; Spanish, English, Dutch
colonisers

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Rediscovery of the texts of ancients (e
...
Ptolemy)
Development of the printing press
Scientific revolution of 17th century
Navigational charts for sailing ships with increasing accuracy
FRA MAUROs WORLD MAP 1459
THE SALVIATI ‘PLANISPHERE’ 1527
MERCANTOR WORLD MAP 1569


Modern Map (1700-1950)
• Observation-based, scientific approach to data collection
• First developed in 18th century France
• Field-surveying technique, refinement of triangulation improved mathematical
method, new method of relief representations
• Increasing use of maps by the state for political purpose (e
...
National mapping
project)
• First national topographic systems in France and England
• Cadastral mapping- for fiscal and juridical purpose
• Increasing number of thematic maps, especially since the 19th century (maps of
measurable phenomenon e
...
Demographic, education, crime, traffic flow)

Digital Mapping
• Development of computer-assisted cartography
• Development of geographical information system (GIS)
• Internet- based cartography
• Democratisation of map making
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g
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g
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g
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g
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Attribute
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g
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g
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Mapping Cyberspace
• ICT
- Physical architecture and topology of network
- Traffic through the network
• Cyberspace
- Hoe to map place that can not be seen
- No materiality
- Transient landscapes- change constantly
- Challenge to ‘cyber and cartographers’


Map Projections
A way of taking the 3-D shaped of the earth and translating it into a 2D map
There are different types of map projections:
• Mercator Map
- Rectangular in shape
- Used mostly for marine navigation
- Advantages: Shows true direction between places the best
- Disadvantages: Land size is distorted or misrepresented near North and South Poles
• Robinson
- Rectangular in shape with rounded edges
- Mostly commonly used as projection
- Advantages: Continents are shown most truest in size and shape
- Disadvantages: North and South are flattened
• Peters Map






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