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General introduction
- Leuven University Press
- Chapter
- Additional Information
15 General introduction Spatial data (also referred to as geospatial, geographic or location-based data) are data that relate to a location on the Earth (Rajabifard et al., 2003a, p.14). Spatial data have always been crucial for governments. From local communities to countries and beyond, governments need information on issues as land ownership, road infrastructure, land use, population registration, economic activities and military assets. Most information in the public sector can, in one way or the other, be linked to a location (Longhorn and Blakemore, 2008). It has been estimated that over 80% of governmental data has a locational basis (Williamson et al., 2003). Knowledge of the location of an activity allows it to be linked with other activities or features in the same or nearby locations. Furthermore, locations allow distances to be calculated, maps to be made, directions to be given and decisions to be made about complex, interrelated issues (Williamson et al., 2003). Government organisations traditionally kept registers and atlases on various topics. An example of this is the Local Roads Atlas (in Dutch: Atlas der Buurtwegen), a series of books that each contain detailed (1/2500) maps covering the entire area of Belgium (Provincie Limburg, 1841). Each map shows numbered road segments and parcels (see Figure 1). In the table section of each book, extensive tabular information can be found on these road segments and parcels. Alterations to the Atlas are kept to date in separate registers. Figure 1 Extract of the Local Roads Atlas (Provincie Limburg, 1841) 16 Apart from the actual maps, as in the Local Roads Atlas, much of the public sector information refers only indirectly to a location, by means of an address, a building name, the crossing of two roads, a marker position along a waterway, or even a description as two hundred meters to the South from the water fountain. Paper maps and registers were not only difficult to adapt to changes in the physical world, especially the combination of information from different maps proved to be complex, involving the use of tracing paper, or even the composition of new maps. The true power of spatial data however seems to lie in the ability to combine information from different sources, with regard to a certain location (Williamson et al., 2003). Figure 2 shows a variant of the original map drawn by dr. John Snow, a British physician who was one of the founders of medical epidemiology, showing cases of cholera in the London epidemics of 1854, clustered around the locations of water pumps.The combination of cholera cases and water pumps on the same map, allowed Snow to relate the incidence of cholera with the presence of contaminated water pumps (Snow, 1855). Figure 2 Cases of cholera and the locations of water pumps (based on: Snow, 1855) The introduction of geographical information systems (GIS) represented a significant development in the handling of spatial data. Masser (2005) states that the impact was similar to that of a word processor on conventional typewriters and publishing practices. Information can be stored, updated and modified in digital form, and retrieved later for use in various applications and output formats. A GIS not only enables the user to manage spatial datasets as separate map layers in a digital environment. The main advantage is the ability to combine and interpret information on a certain location from different layers, including textual, statistical and map data. [3.235.227.36] Project MUSE (2024-03-28 21:25 GMT) 17 At first, GIS were developed as closed applications, with their own specific software packages, data structures and programming languages. Gradually a technological integration with the mainstream IT developments has been reached. The focus was initially on individual use within separate organisations. Although the introduction of GIS might have offered clear advantages to these initial users, the need for bridges between the isolated GIS islands soon became apparent. Searching for spatial data that might be available at other organisations is time-consuming. Similar datasets may be developed by different organisations. Spatial data are not always readily exchangeable, and overlaying different data layers could introduce accuracy errors, which makes it difficult to combine spatial data from different sources. Also the access to spatial data is not always well regulated (AGIV, 2010). Institutional barriers often inhibit the potential use of GIS, by restricting spatial data access and availability. We are now seeing an increasing shift towards the shared use and hence exchange of spatial data across different organisations. In past years, various...