Practical I: An Introduction to GIS and Geographic
Practical I: An Introduction to GIS and Geographic Information Sources A: An Introduction to GIS What is GIS? Why is GIS unique? Why use GIS? Key Definitions The nature of spatial data How does a GIS work? Layers and vectors Relationship of world to GIS GIS and mapping applications
Key stages in using a GIS GIS analysis functions B: Geographic Information Sources Spatial data Geocoding data Attribute data Exercise searching for spatially-referenced attribute data 1 What is GIS? a system for capturing, storing, checking, integrating, manipulating analysing and displaying data which are spatially referenced to the Earth (DoE, 1987) [GIS are] computerised systems for the integrated handling of
spatially-related data (Mather, 1991) GIS rests on the assumption that different kinds of spatial data have common structure, and are processed in similar ways, and that there is consequently value in creating common spatial data handling and processing systems (Goodchild, 1995) GIS is a powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes (Burrough and McDonnell, 1998) 2 Why is GIS unique? GIS handles SPATIAL information Information referenced by its location in space GIS makes connections between activities based on spatial proximity 3 GIS concepts are not new!
London cholera epidemic 1854 Soho + Cholera death Water pump 4 Spatial information handling 1854 Soho + Cholera death Water pump 5 Why use GIS? "A GIS links spatial data with geographic
information about a particular feature on a map. The information is stored as attributes of the graphically represented feature." ESRI 1992 "With GIS it is possible to map, model, query, and analyse large quantities of data all held together within a single database." The Geographers Craft, 1992 6 Key definitions spatial data data that can be linked in geographic space to some feature on a map has both a spatial (where) and an attribute (what) component feature a single entity that comprises part of a landscape which can be represented as a point, line or polygon
attribute a characteristic of a feature that contains a measurement or value for the feature - a column in a data file 7 Spatial data: Are these spatial data? Source: www.esri.com 8 Of course! Spatial reference Attributes Source: www.esri.com
9 10 How does GIS work? - creating a digital world The layer approach Communication Landuse Conservation Historic sites Common referencing framework The object approach S u p e r c la s s B u ild in g A t t r ib u t e s B e h a v io u r S u b c la s s
F a c to ry S u b c la s s R e s id e n tia l S u b c la s s R e ta il B e h a v io u r A t t r ib u t e s B e h a v io u r A t t r ib u t e s B e h a v io u r A t t r ib u t e s 11 The Layer Approach
Thematic data layers ESRI 1994 12 Modelling the real world Vector model y 1 1 20 50 1 2 24 45 1 3 52 55 x Raster model 2 1 0 45
14 Spatial data storage Vector model 7,10 5,9 10 9,8 4,7 2,5 5 polygon
8,6 1,6 6,6 line point 5,4 2,2 4,1 5 10 Raster model
15 Raster model - Pixels and resolution 10 m grid Resolution - the size of the smallest recording unit or the smallest feature that can be mapped and measured (Heywood et al. 1998) 16 Vector data - points, lines and areas Points - x,y co-ordinates representing individual points e.g. trees [x1,y1] Point Line
[x1,y1] Lines - sets of points representing linear features e.g. roads, rivers [x3,y3] [x5,y5] [x2,y2] [x4,y4] [x6,y6] Areas - closed set of lines such as woodlands or a city boundary [x1,y1] [x2,y2]
Area [x3,y3] 17 Vector model Attributes Address: 125 New Bridge Street Use: Residential 18 Vector model topology Connectivity - e.g. street or pipe networks Adjacency - adjacent buildings sharing common walls Containment - one area
within another e.g. building inside land parcel 19 GIS components attributes Database Management System points, lines, areas features layers GIS Spatial Analysis Tool kit
Mapping Package route finding buffering polygon overlay 20 GIS and mapping applications mapping application primary goal is the production of screen or hard-copy maps enables map data to be transferred into a GIS does not generally support topological data structures GIS spatial data with spatial indexing and topology analyse the interaction between different spatial entities query data which has a spatial component or by spatial criteria
create new objects based on these interactions 21 Key stages in using a GIS Data acquisition of both spatial and attribute data (see web page) [Data management] Data analysis Data output produce a map or report (next week) 22 Data analysis analysis of data is the "turning data into information" part of the GIS (distinguishes GIS proper from mapping) whole books have been devoted to spatial analysis GIS analysis can be divided into three types:
general functions single object analysis multiple object analysis analysis resulting in the creation of a new object 23 GIS analysis functions general functions e.g. co-ordinate transformation, modify geometry / attributes of objects, information retrieval analysis - single objects e.g. generalise or smooth lines, measure area etc. analysis - multiple objects e.g. measure distance, network analysis, compute statistics
for a set of objects, establish intervisibility (terrain analysis) analysis - create new objects overlay, dissolve, merge and reclassify area objects 24 Generalisation - exaggeration The features on map A have been simplified and exaggerated to produce map B whilst retaining all its main features. 25 Measurement Distance Area Perimeter 26
Measurement Distance Area Perimeter 27 Measurement Distance Area Perimeter 28 Analysis creating new objects Polygon overlay Very important procedure of GIS analysis which involves superimposing 2 or more map layers to produce a new map layer
Used to answer Where is the best place? type of queries Buffer analysis Creation of a corridor around a main road thus enables the selection of services within a certain distance of the road Visual analysis - buffer around a river based on flow volume to indicate varying discharge along a rivers course 29 Buffering Point - specified distance from road junction Area - specified distance from building Line - specified distance from
road centreline 30 Buffering Point - specified distance from road junction Area - specified distance from building Line - specified distance from road centreline 31 Buffering
Point - specified distance from road junction Area - specified distance from building Line - specified distance from road centreline 32 Merge and reclassify e.g. reclassify river Tyne to 1, everything else to 0 33
Database applications: i.e. queries Spatial - where is 17 Henry Square? Attribute - what is the use of this building? 34 Sources of digital data Spatial (feature and boundary) data Ordnance Survey from EDINA Digimap Bartholomew from MIMAS boundary data from EDINA UKBorders [Geocoding data addresses & postcodes] Attribute data socio-economic
census from MIMAS lifestyle from commercial sources individual researcher sources 35 Feature data: Bartholomew Datasets Great Britain Basis for several road atlases and street maps 1:200,000 scale available in single coverage, National Grid tiles (100 x 100km area) or untiled
(for 25 x 25km or 50 x 50km) up to 18 separate layers British Isles 1:500 000 Grey scale raster images Roads, boundaries and towns as vector overlays also available London
1:5,000 scale 14 layers including raster layer street level, available for Greater London area basis for several street atlases and sheet maps EURO maps 1:1,000,000 scale 20 layers 82,000 towns names Gazetteer Europe
1:1,000,000 scale raster images 36 Boundary data: Digitised 1991 Census Area Boundary Data Digitised boundary data available from EDINAs UKBORDERS Web interface or MIMAS using DBD91 (registration required in either case) 37 Postcode data for geocoding Ordnance Survey based data sets
CodePoint, ADDRESS-POINT PostPoint Post Office based data sets Address Manager based on PAF (Postal Address File) Postcode Delivery Points File Northern Ireland Postcode Delivery Points File Available via Mimas (registration required) Postcodes Census Geography - OSGRs 38 Attribute Data: Lifestyle data Commercially available data see web page Experian Data
Mail Order Shopping Pack Holidays Leisure Home Computers/Internet Motoring Finance Health Insurance Pack Super Pack - all 480 variables Claritas Data
Population Demographics Occupation Holidays Leisure Activities Possessions Newspapers Financial Activities Car Data 39
Attribute data: 1991 Census Small Area Statistics Data Census Area Statistics downloadable from MIMAS using Casweb (registration required) 40 Data from individuals research or spatiallyreferenced attribute data extracted from governmental and non-governmental websites Guide available via http://www.exeter.ac.uk/~ajgibson Exercise: a) 83 students in 20 groups b) each to select a suitable UK-based dissertation-type topic c) find appropriate web-based spatially-referenced datasets d) establish datasets geography and compare with descriptions provided on http://www.statistics.gov.uk/geography/default.asp e) establish whether conversion is necessary (and possible) to utilise spatial datasets listed on Spatial Units.xls
f) email short report (as a word document) to me ([email protected]) by 5pm this Friday. Remember to include names of group. 41 Example Exercise: Educational outcomes, schools and social context (short version) Principal sources of data are provided by the Department for Education and Skills (http://www. dfes.gov.uk/statistics), Ofsted (http://www.ofsted.gov.uk/) and individual Local Education Authorities (e.g. Devon http://www.devon.gov.uk/eal/). Information on private schools is available from various sources such as http://www.ukprivateschools.com/, http://www. indschools.co.uk/ and http://www.boarding-schools.com/. Where individual school data is provided, postcodes can be converted to OSGR grid-refs using http://census.ac.uk/cdu /Datasets/Lookup_tables/Postal/Postcode_Enumeration_District_Directory.htm (registration with Mimas required). Data on Key Stages 1, 2 and 3 performance at LEA- and GOR-level is available from http://www.dfes.gov.uk/statistics/DB/SFR/s0291/contents.html. GOR-based spatial maps are available (listed on Spatial_Units.xls), whilst LEA-data can be converted to 1998 Local Authorities (as listed on Spatial_Units.xls) using the lookup tables accessible via http://aypc. mcc.ac.uk/afpd/luts.cfm. School-level data on KS1-3 can be obtained via http://www.dfes.
gov.uk/performancetables/. This could be mapped using postcode-OSGR linkage as above. 42 1 BANFIELD, Shaun EGERTON-VERNON, Oliver IRELAND, Alice NICHOLLS, Victoria WILLCOX, Jonathan 5 2 BATES, William ELMER, Jonathan JENNINGS, Alice NOWAK, Edward WILLIAMS, Bethan 6 3
BELL, Ewan EVANS, Kirsty JESSON, Sarah OTTEWILL, Sarah WOLLEY, Rebecca 4 BERRY, Natalie EVANS, Verity KANE, David ROBERTS, Gemma 8 BROOKER, David FIENNES, Eleanor MACDONALD, Beverly SHAW, David BILES, Nicola EVERTON-JONES, Aimee
KELLY, Jonathan ROSS, Samuel BIRD, Zoe FERGUSON, Edward LAWSON, Rebecca ROWAN, Michael 7 BRADON, Laura FIELDER, Abigail LEWIS, David SEARLE, Natalie 9 BUCKINGHAM, Laura FITZJOHN-SYKES, Gemma MARTIN, Meriel SMITH, Alister
10 BULLOCK, Steven FOWLER, Lisa MASON, James SMITH, Stephen 11 BURNS, Lucy GOTTS, Naomi MAY, Daniel STEPHENS, Gemma 13 CONGRAVE, Jennifer HARMSWORTH, Amy MITCHELL, Thomas SUMNER, Louise 14 CRITIEN, Iain
HAYDON, Victoria MOHERNDL, Karl SURGEONER, Kate 15 CROWE, Philip HENRY, Emma MOORE, Sarah TAYLOR, Matthew DAVIES, Tara HIGGIN, Louise MORETON, Simon TIPPER, Helen 17 DOWELL, Adam HOLLANDS, Christopher MORRIS, Simon TRENT, William
18 DUNN, Alexandra HORNE, Thomas MURPHY, Sarah VAUGHAN, Nicola 19 DUNSMORE, Thomas HULIN, Sarah NAPIER, Suzi VENNING, Jessica 20 EARLE, Athlene INGLE-FINCH, Andrew NEWTON, Amy VYVYAN-ROBINSON, Joanna 12
CARR, Samuel GRANDIS, Emily MILES, Sebastian STEVENS, Fjola 16 43
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