Presenting spatial data Analyst training course – 23 rd June 2014

Why present spatial data? Geography a major factor in health variations Demographics Industry and occupation Environment Health and social services Highlight patterns in variation (hypothesis generation) See what your local health state is in relation to other areas Correlate two geographical patterns of variation Easy to understand and attractive to look at! 2Presenting spatial data

An example 3Presenting spatial data

The fundamentals GIS: Geographical Information System/Geographical Information Science Both the concept and the software to do and present spatial analysis Any object has two types of information associated: Spatial and Attribute Spatial – grid reference, longitude/latitude Attribute – name, population, height These combine to allow visual display of data, or to analyse data based on geography 4Presenting spatial data

The fundamentals Geographical features can be represented in three main ways Point – Hospital location, case of disease Line – Roads, rivers Polygon – County, urban area, catchment area These are built up in layers, allowing comparison between various features using GIS software Also Raster (not Ratsa!) layers for context 1:50,000 colour map Orientation – or highlighting specific small areas 5Presenting spatial data

The fundamentals 6Presenting spatial data

“You know nothing Jon Snow…” 7Presenting spatial data

Early thematic map example ( Charles Dupin: illiteracy in France (1826) 8Presenting spatial data

Thematic mapping for health Thematic maps are the most common output and can convey information relating to Range – highs/lows Spatial variation Geographical details – e.g. hospital locations Require some thought to avoid common mistakes Can be choropleth or isarithmic: each type has its advantages 9Presenting spatial data

Thematic mapping for health Choropleth maps use pre-existing boundaries Ecological fallacy – grouping by area Can hide small pockets of interest Isarithmic maps use the data to define boundaries Requires more analysis work Could set boundaries to ‘prove’ an issue (MAUP) 10Presenting spatial data

Thematic mapping for health Can be too easy to show everything. Ask yourself what is most important? What is the message? Trends Areas of focus There is an art to data presentation – pick the right colours, and try not to discriminate Colour blind Easy to distinguish Greyscale? Inadvertent association of colour and message Get the right scale. Can you balance an overview with details of ‘hotspots’? What is required? Maybe more than one map 11Presenting spatial data

Are the important areas clear? 12Presenting spatial data

Are the important areas clear? 13Presenting spatial data

Colours 14Presenting spatial data

Scale 15Presenting spatial data

Scale 16Presenting spatial data

Cluster analysis Plotting actual geographical locations can highlight patterns which are not otherwise obvious Must be careful not to try and find a reason for patterns we see – need to test a hypothesis Beware of the MAUP – Modifiable Areal Unit Problem Back up with other statistics 17Presenting spatial data

Cluster analysis – the MAUP 18Presenting spatial data

Cluster analysis – the MAUP 19Presenting spatial data

Same data…different results Most GIS software packages will allow you to do grouped ranges e.g. quintiles of equal count, equal range, SD Can draw quite different conclusions based on which one is chosen What do you want to show? 20Presenting spatial data

Same data…different results 21Presenting spatial data

Same data…different results 22Presenting spatial data

Same data…different results 23Presenting spatial data

Same data…different results 24Presenting spatial data

Thematic maps can be interactive 25Presenting spatial data

Thematic maps can be online 26Presenting spatial data

Software MapInfohttp:// ArcGIShttp:// QGIShttp:// InstantAtlashttp:// MapTubehttp:// 27Presenting spatial data

Data boundaries/index.htmlhttp:// boundaries/index.html government/products/index.htmlhttp:// government/products/index.html 28Presenting spatial data