The Ordnance Survey isn’t above an April Fool’s prank, it seems. For the April 2018 issue of Country Walking magazine, they created a fictional island in the Atlantic Ocean that “had been lost to the sea centuries ago, only for it to have now mysteriously risen out of the waves in need of mapping.” (Its name, “Hy-Breasal,” might have been a tip-off.) In a post on the Ordnance Survey’s blog, cartographer Mark Wolstenholme explains how he used existing OS mapping to create a made-up island in a very short time frame.

After an aborted attempt at cutting up Lundy, I chose the Outer Hebrides’ isle of Pabbay for the main part of our new island. To disguise its origin, I flipped and rotated the island. To achieve that, all the names, symbols and vegetation had to stripped off, and because OS Explorer mapping is a raster image, that meant a lot of pixel selecting in Photoshop. Another restriction with the raster, meant I could only rotate the island by 90 or 180 degrees. Any other angle would re-interpolate the pixels and the print quality would be lost.

To further disguise the island, I looked for a smaller island to add, this time taken from the Orkney Islands. This was joined by the addition of an area of sand and reworked low water line. To finish the shaping, I added a handful of rocky outcrops around the coast as well as some mud, sand and a redrawn high-water line through the dunes. A bigger loch was hand drawn and is unique to this island.

Adding new features and Easter eggs in Illustrator and Photoshop came next. Read the post for the details.