ABSTRACT
A few themes have emerged in the course of the book and it is worth finishing by trying to pull these together. The first is the set of problems caused by the 2D nature of spatial data. This is not a problem which is unique to GIS. Computer graphics and computer-aided design (CAD) software also have to handle 2D data, and in fact uses many of the same data structures and algorithms as used in GIS. Where GIS is perhaps different is in the need to handle large volumes of data and to be able to undertake what are effectively database operations. Where specialist software packages are entirely suitable for computer graphics and CAD they present some problems for GIS. For example, specialist GIS software cannot take advantage of the well-tested and very efficient facilities of modern database software. This approach also makes it more difficult to integrate spatial data with other data holdings. This is not to say that there have not been developments in specialist GIS software such as the inclusion of powerful geostatistical methods and of heuristics for solving real-world problems such as the location-allocation problem. However at the same time there has been a movement of spatial data and GIS methods into mainstream data processing. This leads to the next theme of the book which is that greater attention is now being paid to methods for dealing with 2D data by the computer science community and by the IT industry in general. The early work on GIS was undertaken by a small group of academics, many with a background in geography. This work laid the foundations for modern GIS software but produced systems which were designed to handle small datasets. As soon as the problems which are being handled become very large, then small inefficiencies start to matter and you need systems which are designed for handling large datasets. One of the big changes in GIS in recent years has been much greater use of methods and data structures developed for handling large, non-spatial databases efficiently. This has sometimes involved adapting the techniques for 2D data, and sometimes converting the data to a 1D form so that the techniques can be applied. The third theme, and the factor which is probably driving most change in current GIS, is the explosion in the use of spatial data thanks to the Internet, satellite navigation, and mobile computing. It is difficult to underestimate the importance of all these technologies. When the first edition of this book was published in 2002, GIS was still something which was largely undertaken by trained staff using a desktop computer. The software was becoming easier to use and more widely available but it was still not something designed for the casual user. Now, in 2013, route planning, browsing maps and finding information about places are all tasks which are undertaken everyday by members of the public using what are effectively specialised GIS systems. The user interfaces are simple and intuitive, not least because these systems only offer a limited set of functionality. However, the functionality is powerful and useful and hence is widely used. These systems also draw on databases which are global in coverage but local in scale and also have to serve large numbers of concurrent users often accessing the system over a wireless network connection.
