Techniki GIS – w poszukiwaniu hot spotów przestępczości
Authors: Stanisław Mordwa
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Since the accomplishments of the social ecology school, it is common knowledge thatthere is a thesis about the existence of a strong relationship between crime and space. Since the 1990s, the police has been equipped with various GIS techniques which allowthe discovery of spatial patterns in the distribution of crime. The techniques turned outto be very helpful for effectively combating crime and misdemeanours, since the policewere in a position to identify small individual spaces in towns that were characterisedwith high crime indicators. These places are usually referred to as crime hotspots. Thefactors leading to a concentration of crime in specified places includes: the presencewithin them of attractive crime targets or locations easing the carrying out of criminalacts. From this point of view, one can differentiate three types of hotspot: they aregenerators of criminal opportunities, generators of crime, and places facilitating crime.The basic question of the research is: in what manner, or using what tools, can oneeffectively and objectively identify hotspots in city spaces?The modern city is very socio-spatially diverse. The most important accomplishments in the theoretical problems on the functioning of areas of concentratedsocio-pathological phenomena include the theory of social disorganisation, the conceptof social areas in cities (E. Shewky, W. Bell, S. Williams), and the model of post-moderncity structure (M. Dear). Also repeatedly described in criminological literature are thetheory of “broken windows” (G. Kelling and J. Wilson), the pattern of crime (P. and P.Brantingham), and the perspective of routine activities (M. Felson, L. Cohen). Based on the research findings of Polish researchers, one can formulate severalregularities associated with the occurrence of social pathologies in Polish cities. Firstly,the deprivation areas of cities primarily include town centres and housing blocks, olderblock estates, suburban areas (placed along little-active streets of peripheral placementand along exit roads), and old factory estates. In addition, persistent problem areasin Polish city centres have been in place since the interwar period. So-called povertyenclaves are characterised by amortised living spaces, unemployment, reliance ofinhabitants on social benefits, and are escalated by pathological behaviours: crime, alcoholism, broken/incomplete families, domestic violence. Unusually interesting is thecycle of degradation in downtown areas, presenting the shared arrangement of a variety of unfavourable phenomena leading to spatial and social degradation in the centralspaces of Polish cities. The problems found during the spatial analysis of crime in various cities in Polandare quite broad. Other than the presented disproportion and spatial diversity of socialpathology, the areas most at risk have also been identified. The analysis of criminalhotspots using GIS techniques and tools was undertaken by S. Mordwa and N. Sypion Dutkowska. The region studied in search of hotspots in Łódź was the metropolitan area (Fig.1).The area makes up the city centre, which includes within its reach historical buildingsthat represent the city’s identity. The metropolitan area covers 14 km2 (4.8% of the city), which in 2010 had over 140,000 inhabitants (19.7%) and 2,291 incidents recorded bypolice. The quoted numbers indicate that there were 5.58 times more police incidentsin relation to the size of the area, and 1.36 extra events in relation to the number ofinhabitants.In the article, a review of GIS techniques is made, thanks to which one candifferentiate hotspots. An analysis is made of the garnered results of these spaces,and the advantages and disadvantages are emphasised of the following techniques:cartograms (Fig.3), thematic maps (Fig.3b), point maps (Fig.2), local and global Moran’sI (Fig.4), Getis-Ord Gi* (Fig.5), hierarchical grouping based on the nearest neighbourtechnique (Fig.7), nuclear density estimators (Fig.6), and the K-means method (Fig.8). After reviewing these techniques, a question is raised: which technique is the mosteffective in the study of determining crime hotspots? The PAI indicator is used to solvethis problem, as described by S. Chainey et al. The PAI indicator is constructed in sucha way that the counter finds a proportion of crimes which are localised to the areaof every hotspot. The denominator meanwhile is the proportion of area taken up byhotspots generally. Generally the most effective technique used will be determined bythe highest value of the counter against the lowest possible value of the denominator (remembering that the definition of a hotspot is a small segment of an area in whichmany crimes are registered). It turned out that the most accurate hotspots were obtainedby employing the hierarchical grouping method with the nearest neighbour techniqueand the nuclear density estimators (tab.1). Of all the places of concentrated crime identified in the metropolitan area (determined by the hierarchical nearest neighbour method), the hotspot with the mostincidents identified by police was in a central area called Plac Wolnosci (Liberty Square) (Fig.9). This area is dominated by buildings in the downtown style from the turn of the20th century. Three-storey rented townhouses dominate, which were very high qualitydwellings when they were built. But now they are characterised by a high degree oftechnical wear. The area is intensely built up, and the municipal council is the mainlandlord here. At the same time, it is evident there is a shortage of dwellings with centralheating, with most apartments having a low number of rooms but high population ofinhabitants. It is a substandard area with very low social status. The buildings here(mainly communal townhouses of low standard, known as so-called poor houses) form the worst living conditions in Łódź, while inhabitants mainly belong to the lowestsocial categories (poorly educated, unemployed, low paid). In accordance with otherstudies, the area is characterised by the weakness of the community, which indicatesa reduction or even complete loss of economic strength and social value in the residentsto participate in social life and the city’s economy. The community here is characterized by high rates of unemployment, clearly outlined poverty, and low education.The hotspot of Plac Wolnosci is approximately 14 hectares in size. In 2010,police in this area registered more than 100 incidents. Most often they were cases of pickpocketing (around 25% of all acts) which likely results from the significant volumeof traffic, the many transportation routes which pass through (tram and bus), as wellas the presence of many stops. Victims of theft and robbery (around 20% of the area’spolice incidents) were often regulars of Piotrkowski Street and the nearby Manufakturaarea, who had inadvertently entered the area (to make use of public transportation) from the well-monitored ones. Also common in the hotspot are property damage, burglary of commercial buildings, and car accessory theft. To summarise, the analysis in the article consists of: 1) the presented GIS techniqueswhich turned out to be useful and effective in various social studies of crime. Theirapplication enables the possibility of objectively identifying hotspots. The most effectivetechnique turned out to be hierarchical grouping based on the nearest neighbourtechnique; 2) in accordance with expectations, the most affected by crime turned outto be the very centre of Łódź. Based on the above study, one can conclude that analysis of areas has significancein social studies, since each location is characterised by differing urban environmentqualities, such as its socio-economic status, area history and collective memory,local identity, perception and symbols of the spaces, informal social controls, livingstandards, regulations linked with management, and more. Simply learning the spatialdistribution of hotspots cannot constitute the research aim. Utilising other methodsconcentrated on people and communities requires further investigation of the causesof the appearance of social problems and their relationship with spaces. Further studies could be concentrated on the main problem areas.