Who Left That Hole There? The pitfalls of digitisation

by Dr. Philip Hatfield, Lead Curator, Digital Maps, British Library


Providing increasing amounts of historic content online is an important part of what modern collections do. The reasons for this are simple, digitisation allows collections to be used in different ways and, perhaps most importantly, makes the information they contain available to users who are not able to travel to the location of physical collections easily. For institutions like the British Library and the National Library of Scotland (who are also digitising their Ordnance Survey holdings to create this wonderful resource http://maps.nls.uk/geo/explore/#zoom=5&lat=56.0000&lon=-4.0000&layers=171) this is an important hurdle to pass as we have a responsibility to communities found way beyond our respective cities of London and Edinburgh.

Also, you may be thinking, why not do it? After all, digitisation of collections should be very simple, right? Well, it turns out to be much more complicated than you would expect, with many pitfalls along the road to creating engaging digital content. The first problems come with the original materials. With some, like newspapers, there are substantial issues about the quality of material that has been around for a hundred years but was only really designed to be used for a day. Maps are usually free from these problems but they still come with significant conservation needs before any work can be done. For a project like Know Your Place, where thousands of sheet maps require digitisation to create the finished product, this is a lot of item checking to look for page tares, damaged bindings, chemical ware and many other problems which can develop for a collection that has seen active use for over a hundred years.

There are also issues that can be caused by prior use. For the British Museum (who originally held this collection http://www.bl.uk/aboutus/quickinfo/facts/history/) it was helpful for the sheet maps to be bound into volumes, making them easier to store, provide to readers and use. When it comes to digitisation, however, this is a problem. Bound maps require specialist digitisation equipment, are laborious to move, require more care (to preserve the binding) and are generally slower to move through a machine than loose sheet maps. This is one of the reasons why the British Library (http://bl.uk) and National Library of Scotland (http://maps.nls.uk) have collaborated on this project, fewer of the maps held in Edinburgh are bound together and so they are able to progress at greater speed when digitising their holdings.

Once sheets have been digitised, they have been georeferenced and produced as vectored maps problems still remain; sadly manifesting themselves as holes in the vectored maps used by volunteers. The causes of these holes are numerous, ranging from issues with original production to modern issues over copyright. Some holes are present as a result of the way in which the original surveys were done, a complex and evolving process where execution showed different scales to be desirable, publication highlighted errors in surveying, and so on (a good overview of this can be found in Rachel Hewitt’s Map of a Nation). This means there will sometimes be a hole in the first edition as that sheet was found to contain an error and so only published in the second edition after the area had to be resurveyed (giving a sense of how laborious and impressive the undertaking of the survey was).

Gaps also exist because sometimes areas were not surveyed. This is not the case with Ordnance Survey mapping but the Goad Fire Insurance plans are a useful example. These plans of Bath, Bristol and Gloucester only chart the parts of the city that would be profitable to insurers, businesses, warehouses and industrial areas which required insurance to protect assets and investments. As a result, areas which would not present business opportunities to insurers, such as municipal parks, were often left off the plans. Another reason for gaps is copyright. The material being digitised by the British Library and National Library of Scotland is predominantly late nineteenth century and early twentieth century, meaning, as OS publications are covered by Crown Copyright, that they are now open to out of copyright reuse. However, some Survey products, such as the Grid plans, were only published for the first time late in the twentieth century and are still in copyright. Sadly this means they are not available to the Know You Place project and will result in a few more, small, holes in the map.