## 4 Results
### Local and External Mappers  
Although OSM is based on collaborative data collection efforts by volunteers, companies such as Yahoo Imagery (until 2011) and Microsoft Bing [39] have been supporting the project by providing their satellite imagery to the project's members to trace information directly from the images. This also allowed members to collect information for areas that they maybe never physically visited or where no local knowledge is available. The OSM project does not provide any direct information about the home location of the members. However, prior research has introduced different methods on how to determine an activity spectrum or area of a member [16]. One of the introduced processes has been applied to determine the location of a member for the selected urban areas. The process is collecting information from all changesets provided by OSM for each member. Changesets are rectangle shaped polygons that surround the area in which a designated member has been making changes to the dataset. By utilizing the center points of all changesets that were created for a single member it is possible to create a final polygon which represents the main activity area of a mapper [16]. Based on the newly created polygons a distance between the polygon and the designated urban area can be measured. The measured distance gives clues whether the data contributor is a local or external mapper. For classification purposes the differences were divided into three groups representing a distance of less than 100 km, more than 100 km and less than 1000 km and more than 1000 km. A distance of less than 100 km to the corresponding urban area would indicate a local mapper and a distance larger than 1000 km would represent an external mapper. Figure 7 shows the distribution of local and external mappers for all tested areas. The distribution of the contributors represented in the figure is based on the Senior Mapper group. Similar results were retrieved when conducting an analysis with the Junior and Nonrecurring Mapper groups.  
Figure 7: **(a)** Number of senior mappers per urban area; and **(b)** Distribution of senior local or external mappers per urban area (Oct. 2012).  
Figure 7 clearly shows that not all urban areas merely rely on local mappers. Areas with higher member numbers generally show smaller contributions by external mappers. The statistical analysis, however, does not show any correlation between the two variables for the selected areas (R\({}_{\mathrm{S}}\) -0.16). Cairo, Istanbul, Johannesburg and Los Angeles revealed some surprising results. Although Los Angeles has a higher number of members in OSM than Johannesburg, both urban areas show similar patterns when considering external mapper activities. The largest external mapper contributions were found for Cairo (almost 50%) and Istanbul (more than 50%), indicating that the main activity area of these mappers is more than 1000 km away from these particular urban areas. Reasons for these patterns could be the increased Internet accessibility in other countries or the popularity of these particular areas for tourism, which attracts more external mappers. However, this statement is only based on speculation.