It is also possible to attach scanned images and documents to this database if desired (see Figure 2). Individual crimes can be flagged' and put into a user-generated folder, allowing a skilled analyst to track particularly interesting crimes. When flagged' events are retrieved they can be subjected to the various synoptic analysis functions described above when appropriate. This allows the fuzzy matching' of events, whereby crimes that are not identical but have sufficiently similar characteristics to suggest the same criminal is responsible, can be linked. .
Figure 2: Attaching Scanned Images as Attributes to Pins' .
(Source: Crime Analysis Brochure, 1999, Available from http://www.esri.com) .
1.4 Difficulties of Crime Pattern Analysis Using GIS .
The difficulties in establishing proper GIS procedures for CPA applications were demonstrated when a system for CPA was installed in a sub-divisional police station in Northumbria, using a relational database and 1:1250 digital maps. After 20 months the project had been abandoned and deemed a failure. This was largely due to a lack of design at the initial stages and a lack of understanding of the exact nature of police requirements on the part of the vendor and unreasonable expectations from the police themselves (Openshaw et al, 1991). There is no simple way of automating pin maps through GIS software, and in many cases GIS may be considered an expensive and unnecessary solution. Whereas any clerk can update pin maps, the GIS solution requires specialist training of officers. It also requires that the map be pre-punched' with each pinhole corresponding to individual addresses and the data for these computerised pinholes must be paid for. GIS has the advantages that it can handle many more pins' than can be handled manually and can assign each of them many attributes, but can automated pattern recognition compete with the human brain? Patterns that emerge in the pins may relate to features that are even included on the map, making local knowledge an important tool, especially as spatial patterns often exist only in the eye of the beholder (Barr, 1993).