Making sense of spatial dataAugust 3rd, 2016 By Mairéad de Roiste
Maps are becoming more common place but the skills and knowledge to work with spatial data isn’t as obvious as it first appears. This public lecture explored the benefits of using maps and spatial analysis to explore problems. This talk was given at the National Library on 16 June as part of the cartography series jointly presented by the National Library and Victoria University of Wellington.
Mairéad de Roiste lectures in Geographic Information Science, cartography and all things map related at Victoria University in Wellington. She's passionate about geospatial education and currently heads the national masters in GIS programme across Victoria University, AUT and the University of Canterbury. Her research interests focus on usability, pedagogy and spatial econometric modelling.
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This post is an adapted version of Mairéad’s presentation.
The case for maps
What are you looking at?
A map of Wellington? Think about what you are doing when you look at this map. Do you recognise the location?
What cognitive functions are you using to interpret the image in front of you? And think of how you extend those functions by relating them to the ‘real’ world.
Is this satellite imagery easier to interpret?
Navigation maps can be more abstract – but they’re still useful. Take the London Underground map.
This map is highly abstracted, with distances and angles distorted, but it’s useful to millions of commuters.
A more geographically accurate version is less useful for navigation within the underground system. Without the abstract map’s other features it’s harder to navigate.
This version of the tube map is more geographically accurate – distances are preserved and some contextual information is provided.
The same map techniques have been used in New Zealand by Andrew Douglas Clifford to map New Zealand’s State Highways.
This map doesn’t aid navigation but has received media attention and is available for purchase. The map supports the idea of maps as art. Making a map aesthetically appealing can make an audience spend more time on it.
Historical maps are not just navigation – they’re a way of knowing about the world.
The extra details on these maps, like the ships in the oceans and the surrounding illustrations, convey a sense of place that augments the cartography.
In a digital age, the animation of data can make our understanding of patterns easier:
This map, for example, displays wind for New Zealand:
Why use a map?
There are different reasons to use a map. Some are obvious, like simple navigation. The skills required for visualisation are far more complex:
|Identify and locate own position on a map||Identify||Identify|
|Search for optimum route on map||Compare||Compare|
|Search for landmarks en route||Contrast||Contrast|
|Recognise landmarks on route||Estimate||Discriminate|
|Search for destination||Interpolate||Delimit|
– via Clarke, 2003.
What is spatial literacy? According to Goodchild, it’s the ability to
...capture and communicate knowledge in the form of a map, understand and recognize the world as viewed from above, recognize and interpret patterns, know that geography is more than just a list of places on the Earth’s surface, see the value of geography as a basis for organizing and discovering information, and comprehend such basic concepts as scale and spatial resolution. (2006)
Maps are ways of presenting information, and when they're read they're interpreted.
Ethnicity maps based on census data from 2000 created by Eric Fischer show the racial segregation (or otherwise) of different US cities. Each dot represents 25 residents.
Interpretation of maps found 17 lost pyramids in Egypt in 2011.
Interpretation also finds some more surprising results.
What is spatial thinking?
- Spatial habits of mind – know where, when, how, and why to think spatially
- Spatial concepts
- Spatial thinking skills – which relies on tools, technologies, and concepts
- Critical spatial thinking – the evaluation of quality
New data collection methods are affecting how we should interact with and analyse datasets.
For example, look at the VUW analysis of the Great Kererū Count.
The consequences of bad data can be severe, as when the Limerick County Council demolished a family home due to a plot of land being mislabelled. Or when the police raid the wrong house due to an error in GPS data. Or being the default ‘centre of the USA’ led to trouble for farmowners in Kansas.
The address in question was a ‘cleaned’ version of the geographic centre of the United States. The issue was one of IP mapping, which defaults to the nearest available IP address, but that data was then used for other kinds of mapping, making it look like this farm was the centre of an enormous amount of activity.
Power of analysis
By combining datasets, spatial analysis can create new information. In this case researchers at the University of Canterbury investigated the prevalence of fast food and convenience store outlets near schools. They combined three key datasets and also took into account distance from the schools.
Our own network analysis of Greater Wellington Region commuter data calculated the travel time to work with 4 different types of transport (walking, cycling, driving and public transport). (See T C Daglish, M de Róiste, Y Saglam, and R Law, 2015, "Commuting and Residential Decisions in the Greater Wellington Region". Working paper.)
We calculated the actual commute mode and route as well as alternative locations. By looking at alternatives, we leveraged ‘what if’ modelling to see the effect of possible changes to the transportation network.
While combining datasets is useful and very powerful – it can also lead to some unintended consequences. Please rob me was a site set up to raise awareness about oversharing of personal location information.
The addition of a geographic location can make data more powerful but can also throw up some ethical issues. Family watchdog is a US website which allows users to display the location of sexual offenders around a particular geographical location.
On this site, I explored an area around the Hollywood Roosevelt hotel in Los Angeles, on Hollywood Boulevard. House icons display the location of the hotel, and the markers are different types of sexual offenders on the sexual offenders register.
Each of the markers can be clicked and information about that offender displayed – including their photograph, name, address and details of the convicted crime.
Developing critical spatial thinking
When information is presented, the choices made in that presentation can affect what is communicated.
Here, the first graph makes it look like house prices have more than doubled in one year:
Graphs can be misleading. Here, the axes are very different so give the impression that abortions are significantly overtaking cancer screening by Planned Parenthood in the US.
These two maps of population growth, using the same dataset, look very different and tell different stories:
The next three maps were produced by Masters in GIS students on the GISC 403 Cartography and Geovisualization course in 2015. Each set of maps aims to tell competing stories for the same topic.
The focus of these maps was on different data – one took into account the size of the economy and the other just reported total numbers.
The first map uses ‘calm’ colours to produce a particular pattern of unemployment while the second map uses different but related data and does not give the actual values.
Both colour and data choice for the same locations tell different stories.
Sometimes straight geography misleads. This 2008 US presidential election map has geographically accurate areas, and seems to show that the result was quite close:
This is a cartogram which has distorted the geographically accurate areas to take account of actual population. The map shows that more of the population voted for the ‘blue’ candidate.
Colour and our interpretation of colour plays and important role in how we evaluate maps. Blue used to be associated with the republicans and now we expect the opposite. This image is from CBS in 1980:
The attraction of available data
Just because the data is available doesn’t mean we should map it. We need to ask questions – is the data appropriate? Backing up visual interpretation with statistics is important to ensure we find real patterns
And we need to understand that though the map might correlate with something, it doesn’t mean that it causes it.
Testing our assumptions
Research needs to be done to better understand how we can create better maps as well as how we can develop critical spatial literacy:
- What map designs are effective?
- How much of an effective map design is dependent on data?
- What other factors are involved?
- How can we measure critical spatial thinking?
There is a skill shortage in geospatial work in New Zealand, according to organisations we surveyed. However, government is increasingly recognising this, and change is happening.
Take home points
Advances in mapping tools, technologies, and concepts are significant, and positively affect our interaction with the world.
However, we should critically examine the maps we use.
Backing up visual interpretation with analysis is important.
Research on how we use maps and spatial literacy is evolving, but there’s still a long way to go.
S W Bednarz and K Kemp, 2011. "Understanding and nurturing spatial literacy", Procedia - Social and Behavioral Sciences, 21, 18–23.
T C Daglish, M de Róiste, Y Saglam, and R Law, 2015. "Commuting and Residential Decisions in the Greater Wellington Region", working paper.
M de Róiste, 2009. Geographic information in eLocal government: evaluating online mapping applications in Irish local authorities",Irish Geography, 42(2), 165-183.
M de Róiste, 2014. Filling the gap: The geospatial skills shortage in New Zealand,New Zealand Geographer, 70(3),179-189.
M de Róiste, M Gahegan, P S Morrison, M Ralphs, and P Bucknall, 2010. Geovisualisation and policy: exploring the links,Official Statistics Research Series, 5.
M F Goodchild, 2006. The Fourth R? Rethinking GIS Education.
National Research Council, 2006. Learning to Think Spatially: GIS as a Support System in the K12 Curriculum, Washington, The National Academies Press.