Enter Computers Historical atlases are aimed at many different markets, from classrooms to coffee tables. In general, they became more visually appealing from the 1970s. This had much to do with design conventions and also with popular expectations of illustrative materials, whether in atlases or elsewhere. The map of the resurgence of Muslim power 1520-1639, stretching from Bengal to Morocco, offered a vivid perspective that brought the centres of the Muslim world into prominence. Thanks to commercial pressures, publications policies and the nature of the historical atlases increasingly available, the understanding of what constitutes an historical atlas shifted in the 1980s and 1990s away from the heavy emphasis on maps that characterized most works produced earlier in the century.
Technological change continues to be important.
Computers rapidly construct spatial information systems containing diverse interrelated layers of data, instead of the paper map with its essentially static character. The atlas in hard copy is now subsequent to a computer atlas and is indeed a fixed and rigid form of the material in the computer. That material can be scanned on screen, and such a process is both interactive and far less costly than publication in book form. Increased and improved information was also provided for historical cartography as a consequence of the use of the computer as an analytical tool. This made it far easier to scrutinize data for patterns and relationships.