It has been estimated that there are over 50,000 carefully preserved paper maps still in existence, showing the estates, townships and parishes of Wales as they looked in the 17th to 19th centuries.  These precious historical documents are dispersed across national archives, regional museums and private estates all around the world, making them not only hard to access, but also unknown to most people who have an interest in Welsh history.

The Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW) or Comisiwn Brenhinol Henebion Cymru in Welsh, in conjunction with Bangor University, wanted to find a way to collate these invaluable ancient maps of Wales and make them accessible to everyone.  Rather than simply scanning each map and creating a database of digital copies, however, the organisation wanted to knit them all together and overlay them onto modern day mapping to help people see and understand land changes over centuries.

Initially, RCAHMW focused on six parishes in North East Wales and assembled maps from dozens of sources, including the Duke of Westminster’s Grosvenor Estate.  These ancient maps included tithe maps, originally commissioned to support the collection of taxation between 1836 and 1860, as well as enclosure maps from 1800 to 1830, drawn up at the start of the industrial revolution in Wales.  Looking further back in time, the project team compiled hand-drawn estate maps from the early 1700s, and some even older old estate maps dating from 1620, decades before the English Civil Wars.

RCAHMW digitised these old maps, along with the earliest Ordnance Survey maps, created in three scales between 1869 and 1874.  It used ArcGIS Pro to geographically align all these historic resources with modern mapping.  This was achieved by creating as many as 500 control points, such as the corners of fields, which are unlikely to have changed much over time.  The organisation then used the spline feature in ArcGIS Pro to gently adjust the hand drawn lines and features from the ancient maps until they lined up with the same features in the most up-to-date geographical surveys.

As part of this georeferencing process, RCAHMW vectorised 35,000 individual polygons (such as fields and rivers) over an area of 125 km².  It also captured supplementary information from the ancient paper maps that may have been forgotten over time, such as the names of landowners, commonly used field names, tenants, land use, the extent of common areas, township boundaries and the usage of estate buildings.

Next RCAHMW created a web app in ArcGIS Online, called Deep Mapping Estate Archives, that allows people to explore the maps through the ages and carry out geospatial analysis.  Users can compare landscapes at different points in history and click on any location to open a pop-up box and discover who the landowners or tenants were hundreds of years ago, for example.  The web app is presented in a Deep Mapping website, originally created with ArcGIS Web App Builder and recently updated to ArcGIS Experience Builder, that presents information about the project bilingually in English and Welsh.  Some of the maps are also available to be viewed in 3D, utilising ArcGIS Web Scene.

Modern-day accuracy applied to ancient maps
Through this project, RCAHMW has demonstrated how ArcGIS Pro can be used to effectively capture, geo-reference and vectorise ancient maps. The organisation has transformed historic documents with variable quality into a geographically-accurate, modern-day digital atlas. Recognising this, Jon Dollery, Mapping Officer at RCAHMW, observes, “ArcGIS Pro has enabled RCAHMW to take the accuracy of today and apply it to the past.”

Easy access to rare archived records for everyone
By creating a Deep Mapping app with ArcGIS Experience Builder in ArcGIS Online, RCAHMW has achieved its goal of making exceptionally rare, archived, paper maps acessible to everyone. Free to use, the app is already igniting the interest of members of the public, local historians, educators, academics, social history researchers, local developers and environmental consultants. “Maps that were locked away in archives around the country are now in one place, where everyone can find and enjoy them,” Dollery says.

Greater insight into 400 years of landscape change
By enabling historic maps to be analysed and compared with modern maps, the Deep Mapping app reveals 400 years of landscape changes in Wales that were previously unknown or unrecorded. It is possible to see, for example, where hedgerows have been lost and how river courses have moved over time. RCAHMW anticipates that this insight will be used by developers, environmental consultants and local councils to inform development and conservation initiatives, such reinstating woodland in places where it used to exist.

A deeper appreciation of local history
The Deep Mapping app has received enthusiastic feedback from the residents North East Wales who are fascinated to learn more about their villages and towns. People are using it to see who common land was awarded to 300 years ago, learn where medieval strip farming took place, rediscover lost place names, explore historic estates and gain a deeper appreciation of their local areas. As Dollery concludes with pride, “This initiative really is stimulating interest in local history, and we look forward to expanding it to cover the whole of Wales.”