The horizontal line wending its way across the middle of the image above is a 2,000-year-old Roman road. It was recently detected by David Ratledge, an amateur archaelogist, using Environment Agency data gathered by laser scans - in this case, of the remains of the ancient settlement of Vindolanda in Northumberland.
The agency uses Light Detection and Ranging (LiDAR) to scan the British landscape, then puts the measurements on to its geostore.com site.
Using the data - and some open-source geographic software which turns lists of terrain heights into 3D maps like the one on the left - Ratledge spotted the buried road.
"What you're looking for is a long, straight line or ridge," said Ratledge. "If it goes across many fields, you've probably got a Roman road." The trick? Don't confuse them with pipelines.
When Ratledge spots something on his 3D map, he looks for clues "such as small bridges where the road would have crossed a stream". Ratledge has found seven portions of roads and a full one that goes from Lancaster to Ribchester. Before LiDAR, Ratledge, who has been searching for 45 years, would "look for bumps in the field on aerial photographs".
This article was originally published by WIRED UK
