July Visualisation – 3 in 1 from a thematic map

July Visualisation – 3 in 1 from a thematic map

July Visualisation – 3 in 1 from a thematic map

For this month’s visualisation we took a thematic map from one of our previous blog posts on the drive time accessibility to COVID testing centres around the UK. With this thematic map we used various techniques in QGIS for create different outputs.

HEX map  

A hex map, or hex board, is a game board design commonly used in role-playing games. Since 1961 hex map has been the favourite for game designers (Dussault, 2020). Its popularity is due in-part to the small regular hexagons of identical size (Hutcheson, 2020), in which the map is divided into. 

Hex maps have become the standard when visualising data where the sizing of the geographical region is unimportant, therefore, a hex map removes that artificial nature of more weight being placed on larger states as all states appear the same size (Flerlage, 2020). Another example of hex maps usage, are nationwide elections, showing the voters choice in various counties. 

Hex maps are a mapping technique that many people have covered, but there are several different techniques for making one. For instance, hex binning (Smith, 2020) is a technique used to aggregate a large amount of points into hexagonal grids. 

For our July visualization, we took a thematic map created in TRACC which represented the driving time to COVID-19 Testing Centres in the UK. 

This thematic map is composed of a large number of points, however, applying this hex tool used in QGIS, this data was shown more simply. 

Image 2Thematic Map provided by TRACC and Hex map created depending on amount of points per polygon. 

 

How was our Hex map created? 

 

We firstly created a grid which was amended covering just the area of the UK.

Image 3. Parameters and grid created in QGIS

  

Once we had this grid, we then merged our points data to the grid using ‘Count points in Polygon’ in QGIS to get our Hex map. Doing this, we transferred all data related to our points (from TRACC) into each polygon of this grid. 

Image 4Hex map created based on the hexagonal grid generated in QGIS. 

 

 In addition to this, we made a classification considering the travel time values which allowed us to achieve the following map.   

Image 5Hex map classified in base of Thematic points values. 

 

This map shows the number of points per location based on driving time to COVID-19 Testing Centresit’s a great idea to show accessibility to those destinations in this case, particularly during the morning when contending with commuter traffic. 

The final map has been created making a classification of 10 ranges from 0 to 1400 amount of points per polygon. 

 Heat Map

A Heat map is a graphical representation of numerical data that uses a system of colour-coding to represent different values hence, each individual data points contained in the matrix are represented using different colours (Healy, 2020) 

Heat maps have been around since the 1800s and have since evolved into what they are today. The first known usage of Heat maps is credited to Loua in 1873 (Khongthaw, 2020) 

Heat maps are visually and easy to digest for the viewer as it simplifies numerical data using a colour scale. Heat maps are versatile and adaptable as they can record and present both absolute and derived values (Khongthaw, 2020), just naming a few advantages.  

Some examples of those graphical representations: 

Images 6, 7, 8. Top left – Geographical Heat maptop right – Website Heat mapbottom image – Heat map in Sports (Khongthaw, 2020)

On this new visualisation, we have used again started with the thematic map created in TRACCMoving on this data into QGIS, we applied ‘Heat map (Kernel Density Estimation)’ technique using a radius of 30000 meters and a pixel size for X and Y of 2000. 

The output is a heat map which had been classified using 5 ranges from Up to 2 (first range) to 1700 as a maximum.  

As well as the hex map, heat map shows locations from higher to lower amount of points which provide us with an idea of how is the accessibility to COVID-19 Testing Centres based on its Driving time on the AM Peak.   

Image 9. Hex Map        Image 10. Heat Map       Image 11. Heat map over the Hex map which shows correctly how both outputs can give us information about the accessibility to COVID-19 Testing Centres.

 

Overall, these are good methods to apply if you want to see the same data in different formats which might highlight alternative correlations in the data.

 

Keziah is the Digital Marketing Executive at Basemap Ltd. She has almost 2 years experience in the digital realm after graduating from the University of Plymouth with a BA in Illustration and a MA in Publishing.