The past, present and future of 3D geology in BGS

In its role as a national geological survey the British Geological Survey (BGS) has produced paper maps of Britain’s geology at a series of scales for the past 170 years. Over time these have become more detailed with the one-inch (1:63 360) scale being the benchmark in the mid 19th Century up to today, where 1:10 000 is the scale of primary survey considered appropriate for modern needs over most of Britain’s landscape. Geological maps often require another geologist to understand them fully; the surveyors’ spatial ideas, models and concepts can never be properly represented in a 2D map output, and so, to-date, much knowledge has been lost to the science and to the users. In 1815 William Smith was already addressing the need to present the third dimension of the geology as well as the surface arrangement of units. Over time, cross-section drawing became more refined, resulting in outputs such as fence diagrams, ribbon diagrams and block diagrams to reveal the 3D structure, while contoured surfaces were used to show the spatial position of individual horizons such as major unconformities or the thickness variations of units or sequences (isopach maps) Today, nearly 200 years after Smith’s first map was published, BGS has nearly finished the systematic survey of the geology of Britain at the large scale (predominantly 1:10 000) that is required for modern needs; in addition BGS has recently compiled and published all existing data as 2-D digital geological maps of Britain (DiGMapGB) at scales up to 1:50,000 (Jackson & Green, 2003). From 2000, the next major challenge facing BGS and other national surveys has been to begin the translation of their traditional 2D geological map outputs into fully interactive 3D geological models of the subsurface.