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What are Geographical Information Systems (GIS) & ArcView GIS software?
• What is a Geographical Information System (GIS)?
• Introduction to ESRI ArcView 3.x
• Social science / population geography relevant GIS procedures
Paul Norman
• Cathie Marsh Centre for Census & Survey Research
GIS that the Victorians did for
us!
Charles Booth (poverty maps, 1898-9)
John Snow, (cholera, 1854)
Asthma rates & main roads
Violent crime & deprivation
21st Century GIS
GIS definitions
• GIS A computer system for the input, storage, editing, manipulation, transformation, analysis and output of spatial data
• GIS is (effectively) either an overarching way of organising your spatial data or software for carrying out the above
• Spatial data Data with some form of geographical reference that enables it to be located in two (or three) dimensional space e.g. a grid reference or administrative area code
What can I use GIS for?
• Basic GIS functionality:– Spatial data input and management– Combining datasets (linked by location)– Output (e.g. drawing pretty maps)
• Socio-demographic data:– Distributions of population-related
phenomena (e.g. mapping SMRs)
GIS ‘vector’ & ‘raster’ models
• Vector (e.g. ArcView)– Geometric Cartesian (xy) co-ordinates
• Including projection information• Longitude/latitude, National Grid
– Maps world as discrete graphic features • Points, lines & polygons
– Links to a database for ‘attribute’ storage • Age, sex, deprivation score, area code
• Raster (pixel based, not basic ArcView)– Used for images, environmental data
GIS vector model
Points?
• Houses
• Hospitals, schools
• Cancer cases
• Crime incidents
• Mobile phone masts
• Postcodes
(Some ‘buts’ in a minute!)
Lines?
• Roads
• Footpaths
• Rivers
• Railways, canals
• Pipelines, cables
Polygons?
• Administrative boundaries
• Lakes
• Buildings
• Urban extents
England & Wales
Government Office Region
Wards
Local Authority District
Output Areas
Administrative & Census geographies
But … points, lines & polygons
• Scale dependent– Buildings / Cities: points or polygons?– Postcodes: points, lines or polygons?
Vector GIS digital data
Text files of lists of xy coordinates
• Points = single NGRs
• Lines = lists of NGRs
• Polygons = lists of NGRs that form a loop that knows it’s a loop!!
Polygons with common boundaries are listed separately
ArcView not very clever at topology
Attribute data
• Database (in .dbf format for ArcView)
ArcView 3.x GIS
• Vector-based GIS• Windows GUI environment:• Help system• Task-specific menu & button availability• Extensions for more functionality
Other software …• ArcInfo• MapInfo
Project window
• Views (maps)
• Tables (database)
• Charts (graphs)
• Layouts (printables)
• Scripts (automation)
View window for mapsMenus, buttons
Symbol window
Themes = Shape files = maps Scale, NGR
Layered themes
Zoom
‘Table’ = database of attributes
Records
Fields
Menus, buttons
‘Layout’ = printable mapMenus, buttons
GIS procedures relevant to social sciences & population geography
• Creating thematic / choropleth maps
• Clipping & intersecting polygons
• Point in polygon
Creating a choropleth map in ArcView
Calculate results …
Unique area code to join data to digital boundaries
Creating a choropleth map in ArcView
What do I need to create a map in ArcView?
Digital boundary data:
• UKBORDERS http://edina.ac.uk/ukborders/ using Athens password or ONS CD for Census or ask!
• Extract geographical scale of interest
Some results (e.g. Census data from Casweb):
• Text file (comma or tab delimited) but with .txt extension. Or …
• Dbf file
• Must have alphanumeric codes that match the digital boundary area codes (& match for time & definitions)
Attach results to digital boundaries & make pretty map!
More examples … health
More examples … deprivation
More examples … total fertility rate
More examples … voter turnout
Clipping & intersecting polygons …
Clipping & intersecting polygons …
Change in legal definitions
Blue = 1991
Red = 2001
Point in polygon
Individual level data, located by postcode (points)
Attach NGRs from a directory
• Postcode enumeration district directory
• All fields postcode directory
Which polygon does each point lie within?
Can attach contextual information (e.g. ward deprivation scores) to individual data
Point in polygon
In which ward does each postcode lie?
Haldens ward 1991(•)
Another point routine …
Distance from one point to all others
GIS within CCSR
If you think you’re going to …
• Organise, manipulate, join spatial data
• Illustrate some results using a map
Ask & I’ll help
Always retain geographical reference codes (even if not using GIS software)
Short course?
• GIS for Social Science & Population Geography