Open Data Reveals Roman Roads

David Rateledge, former head of Lancashire County Council’s GIS unit, has been spending his retirement looking for evidence of roman roads in the county and has recently discovered the road which connected Ribchester and Catterall.

He started his investigations several years ago, using Environment Agency LiDAR in the form of JPG picture files, but then progressed to using grid data. He imports the bare earth and surface LiDAR data into Open GIS software package QGIS and experiments to find the best hill-shading angle. An illumination angle perpendicular to the road alignment casts visible shadows from the road embankment (known as the agger) rendering it visible in the image as it passes in a straight line across several fields.

He found that rather than following the route hitherto shown on the Ordnance Survey map, the road took a very sensible and economical route via Longridge and Inglewhite to Catterall, near Garstang, a distance of 10 miles. Here it joined another Roman Road, the main road from the south heading to Lancaster. As David says, “The alignments used are typical of Roman engineering, running straight for several miles but cleverly dog-legging up to Longridge to reduce the gradient. Site visits have confirmed it is real with several stretches surviving, albeit somewhat worse for wear. This was to be expected given that the Romans stopped maintaining it over 1600 years ago!”

Environment Agency LiDAR is now supplied as open data from http://environment.data.gov.uk/ds/survey#/download

Visit: http://www.romanroads.org/gazetteer/lancspages.html