In 1854 the English physician John Snow tracked down the source of a severe cholera epidemic in London - a public water pump in Soho. By pinpointing outbreak locations, roads, water lines and property boundaries onto a map, he discovered that the outbreaks followed the water lines, ultimately revealing the water pump as the point of origin. This was an early example of how underlying patterns can be visualised by layering data on to a map.
The English geographer Roger Tomlinson introduced the powerful tool of computerised GIS (geographic information system) in the 1960s. While working on the Canadian Land Inventory maps he proposed to automate map analysis with computers, and led the development of the pioneering Canadian Geographic Information System.
With the advances in computer and satellite technology GIS has since transformed the way spatial data, relationships and patterns can be visualised, processed and analysed. It is used at all levels of society, including local and national government, research institutions and businesses, and across a wide range of areas – ranging from public health and epidemiology, crime mapping and waste management, through to oil and gas exploration, agriculture and military defence.