Introduction to geographical data and

GIS

Carol BlackwoodUK Data ServiceEDINA

UK Data Service Census Support census geography courseUniversity of Edinburgh6th June 2013

[digital] Geographical data

• How geographical features are represented digitally

• Types of data:• Vector Data – points, lines and polygons

• Raster data – continuous grid where every cell has a value e.g. colour, terrain height

Vector geometries

Image courtesy of http://elogeo.nottingham.ac.uk/xmlui/bitstream/handle/url/66/2_VectorData.pdf?sequence=1

Raster data

Image courtesy of http://elogeo.nottingham.ac.uk/xmlui/bitstream/handle/url/69/5_RasterData.pdf?sequence=1

Data Formats

• Some formats you will come across

Vector Raster TabularSHP ASC CSVMID/MIF GRD DBFTAB TIFF TXTKML ECWGML JPGDXF IMGGPX GIF

GIS – Geographical Information Systems

• We use GIS applications to handle spatial data

• Computer-based information systems to aid solving spatial problems and decision making

• “a system for capturing, storing, checking, integrating, manipulating analysing and displaying data which are spatially referenced to the Earth” (DOE 1987)

GIS

• Data organised and stored as a collection of layers

• Each layer contains similar features e.g. rivers, roads, ward boundaries

• GIS functions: measure, query, overlay, buffer, network analysis, modelling, data presentation and much more.

GIS – common desktop software

• Commercial• ArcGIS • MapInfo

• Open Source• Quantum GIS• GRASS• gvSIG• uDig

ArcGIS

• Made by ESRI• Most popular GIS system used commercially and in

academia• Lots of support available • Can be complicated to get to grips with as lots

tools and options• Available through Eduserv CHEST or by

Educational Licence

Mapping with GIS

• Core function of any GIS is creating and displaying maps

District outlines

DIGITAL BOUNDARY DATA

Census Aggregate Statisticse.g. Population by district of SW England

=

Map displaying population of SW England

Spatial Analysis

• GIS functions that are carried out to extract new and additional meaning from GIS data

• Types of analysis varies with subject area, but use common GIS functions

• e.g. town planners assessing the impact of a new shopping centre

• e.g. social scientists looking at the relationship between deprivation and access to amenities

• e.g. ecologists evaluating the impact of a new windfarm on wildlife

Spatial Analysis – common functions

• Buffering – points, lines and polygons

• Selection by attributes or location• select all with IMD score greater than X• select features within local authority X

Image courtesy of http://elogeo.nottingham.ac.uk/xmlui/handle/url/73

Spatial Analysis – common functions

• Measurements • How many KM between point X and point Y• What is the area of these parcels of land?

• Interpolation• Use rainfall values from weather stations to create an

average rainfall surface

Practical Exercise A

• Practice adding different datasets into ArcMap

• Amend layer symbology

• Select vector map features