The foundations of geographical analysis

How mapping was first used to display and analyse data


We use our GIS products to analyse and present data in a geographical context. Displaying data on maps makes it easier to understand as well as giving a new perspective on a problem. Using a GIS to prepare and present data has become increasingly popular over the last 20 years and improvements in computer processing power and internet speeds make it easier than ever to put data in a spatial context. But graphical displays of data on maps were around long before computers. Geographers, physicians, philanthropists and historians have been using maps to analyse and present data for 100’s of years.


Mapping population density

Population maps for France in 1830 were produced by a Franciscan Friar Armand Joseph Frère de Montizon, he produced a dot distribution map where each dot represented 10,000 people. The dots were arranged on a grid where the distance between each dot decreased as total population increased, so the dots for a particular département (the administrative areas of France) all fit within that boundary. The map at a glance shows total population as well as population density.


Population of France by departement.

Population of France by département.
Image: Wikimedia Commons.

Saving lives with location analysis

In 1854 Soho in London was ravaged by cholera. A York born physician, John Snow, was investigating the causes and spread of these outbreaks. Snow recorded the location of each cholera case on a map and interviewed the households concerned. He recognised that the majority of cases were clustered around a local water pump. Snow used geographical and statistical analysis to link the cholera incidents to the water supply. Further investigation showed that the water from the infected pump was being contaminated by an old cesspit.

Snow wrote:

On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the [Broad Street] pump. There were only ten deaths in houses situated decidedly nearer to another street-pump. In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad Street, as they preferred the water to that of the pumps which were nearer. In three other cases, the deceased were children who went to school near the pump in Broad Street…

With regard to the deaths occurring in the locality belonging to the pump, there were 61 instances in which I was informed that the deceased persons used to drink the pump water from Broad Street, either constantly or occasionally…

The result of the inquiry, then, is, that there has been no particular outbreak or prevalence of cholera in this part of London except among the persons who were in the habit of drinking the water of the above-mentioned pump well.

I had an interview with the Board of Guardians of St James's parish, on the evening of the 7th inst [7 September], and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day.

John Snow, letter to the editor of the Medical Times and Gazette

Map of 19th Century London

Clusters of cholera cases in the London epidemic of 1854. 
Image: Wikimedia Commons.

Mapping social trends

Baron Pierre Charles François Dupin was a mathematician, engineer, economist and politician. His work on thematic and statistical mapping in 1826 used colour to display data over a map. The first "cartes teintées" (coloured map in French) showed the distribution of illiteracy in France.

The term "choropleth map" was introduced in 1938 by the geographer John Kirtland Wright. These maps colour regions and areas within geographic boundaries according to the underlying data. The term is often used interchangeably with “heat map” which also uses colour to display information. The main difference is that a “choropleth map” works to geographical boundaries but heat maps can be more abstract.

Adding an extra dimension with contour lines

Maps that show lines linking things of equal value have been produced for centuries. In 1584 a map showing river depths was produced by Dutchman Pieter Bruinsz, this map was the earliest known isobath (same depth). Depth measuring charts with contour intervals of 1 or 10 fathoms were produced by the great seafaring nations of the enlightenment. Beginning in the middle of the 18th century, maps with lines showing the surface of the land were produced across Europe. Most commonly used to describe topographic and hydrographic features, maps showing lines of equal value are used for pressure (isobar), temperature (isotherm) and time (isochrone). Using a contour line displays 3 dimensions of data over 2 dimensions.

Using maps to display data in a geographical context has long been a useful tool. The earliest examples were hand drawn on maps. With the advent of GIS you can take data that has a geographical component and display it in an easily understandable form.

Choropleth map of France

1826 choropleth map of France. 
Image: Wikimedia Commons.

Our other blogs

Mapping for local projects

Recently, we were contacted by a company responsible for organising charity door knockers. They needed more than 9,000 postcode sectors mapped at A4 size to pass to ground staff showing street level detail. This would enable them to use maps at a local level to plan fundraising routes and clearly define territories for each agent.

All you need to know about postcodes but were afraid to ask

The humble postcode has been around for years. We look at how postcodes are used and what led to their introduction.

Google Fusion Tables

After almost 10 years of service, Google are to retire their Fusion Tables product at the end of 2019. This tool was very useful got visualising and sharing large amounts of tabular data - particularly amongst small and mid-sized businesses. So what can we do to fill the gap left by this tool?

The foundations of geographical analysis

Displaying data on maps makes it easier to understand as well as giving a new perspective on a problem. Using a GIS to prepare and present data has become increasingly popular over the last 20 years, but graphical displays of data on maps were around long before computers came along.

Who spends most on Fruit and Veg

National Vegetarian Week (#NationalVegetarianWeek) this year runs from 13th to 19th May. What better opportunity to highlight how GIS mapping can be used to create marketing campaigns and raise awareness of the benefits of eating more fruit and veg.

Meet the team: Toby

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More than 64 million people live in the UK, each with their own outlook, priorities, needs and way of life. Geodemographic profiling offers a way to group these individuals to try and identify the right audience for your product or service.

Postcode to postcode drive time and distance

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Living Costs and Food Survey

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Using Beacon Dodsworth's scripting technology to showcase demographic and geographic trends.

What is GIS software?

A Geographical Information System (GIS), is a tool for analysing, visualising, managing and presenting data that is related to a physical, geographical location. That link to geography is the key difference between GIS and other data visualisation techniques.

Mapping GP prescription data

An article by Allan Brimicombe (Head of Centre for Geo-Information Studies at the University of East London) & Pat Mungroo on using GP prescription data to understand health needs.

What has the census ever done for us?

How Census 2011 can be used to help organisations with demographic analysis.

Social change over 10 years

The next census isn’t due to take place until 2021 so we thought it was a good time to take stock of some of the changes and trends we noticed between the 2001 and the 2011 census. What difference does 10 years make to our society and the people that live within it?

How to back up your Prospex data

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The power of postcode sectors

Postcode sectors are aggregations of individual postcodes and they provide meaningful geographical reporting areas in any GIS. However, they aren't as easy to map as you might think. Here is how we do it.

Where is the North

We've used the territory manager tool in Prospex GIS to split the UK into north, south and east and west with equal population counts.

Geodemographics and the University of East London

The University of East London explain how they have been using our P² People & Places geodemographic classification.

Household spend on fruit and vegetables

Using GIS mapping to visualise, analyse and present data in a geographical context.

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