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Britain’s largest islands

28 Jun 2018
Ordnance Survey
CartographyUsing GI and maps
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british islandsGreat Britainislandsopendata

Disclaimer: please note that due to the Covid-19 pandemic, the poster is temporarily unavailable.

Great Britain is an island in its own right, but aside from the mainland, there are hundreds of islands around the British coast, many uninhabited*. Inspired by David Garcia’s data visualisation of the Philippines, our GeoDataViz team worked with Alasdair Rae at the University of Sheffield to explore Britain’s largest islands.

They found that there are 82 English, Scottish and Welsh islands larger than 5km2. Scotland boasts the vast majority with 71, not surprising when you consider the Outer Hebrides, Shetland and Orkney and other beautiful islands off the coast. Wales had just 2 entries and England 9.

The team used Boundary-Line to define the area and length of coastline for each island, with some interesting results. While Lewis and Harris topped the tables for being the largest island by area and boasted the longest coastline, not all islands had such a correlation. North Uist (shown below) was the twelfth largest island, but has the fifth longest coastline. Conversely, Arran was the eighth largest island but has the eighteenth longest coastline.

Adding in data from AddressBase, the GeoDataViz team compiled the number of residential addresses on each island and quickly realised that having the largest area does not equate to having the most addresses. Mull is the fourth largest island, but eighteenth when you look at addresses. Portsea Island tops the table for most residential addresses, but is 38th in the list of islands be area.

How we created the visualisation of Britain’s islands

To create the beautiful islands poster, our GeoDataViz team loaded the data into a PostGIS database. From here, they could analyse the data to calculate island area, coastline length and residential address counts. Once completed, they imported the data to QGIS, where we applied colour schemes (we used our GeoDataViz Toolkit for this) and other styling elements. Each island was exported separately and then imported into Adobe Photoshop to produce the poster layout and apply the final touches.

Alasdair complemented this with a gif to showcase more of the islands’ data. Alasdair has been a keen user and sharer of our data since the OS OpenData portal went live in April 2010. He formerly led the MSc in Applied GIS at the University of Sheffield, of which Joe Harrison (the poster designer) is a recent graduate, and has a longstanding interest in geovisualisation so he was an ideal person to collaborate with on this project.

Test your knowledge of Britain’s largest islands

Try out our quiz and see how well you know the islands off the mainland. You can share your score with us on Twitter.

Facts and figures

Top 5 islands by area

  1. Lewis and Harris
  2. Skye
  3. Mainland, Shetland
  4. Mull
  5. Anglesey

Top 5 islands by length of coastline

  1. Lewis and Harris
  2. Mainland, Shetland
  3. Skye
  4. Mull
  5. North Uist

Top 5 islands by residential addresses

  1. Portsea Island
  2. Isle of Wight
  3. Anglesey
  4. Isle of Sheppey
  5. Canvey Island

Find out more

If you’d like to look at the islands’ graphic in more detail, you can download it from our Flickr page.

* Note we are looking at Great Britain’s islands, so this doesn’t include Northern Ireland’s islands, the Isle of Man or the Channel Islands. You can see more about the difference between Great Britain, the United Kingdom and our Crown Dependencies in this blog.

Ordnance Survey
By Ordnance Survey
Press Office

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