The Structure Catalog - Exploring global refugee camp morphology using satellite imagery and cluster analysis

Abstract

In the current situation of refugee camps, maintaining an overview is difficult. Does their structure and morphological composition have an influence on this? In order to gain insight in this regard, the aim of this study is to analyze the morphology of refugee camps throughout the world, gathering information in a comprehensive register - the Structure Catalog. Firstly, the structural features which contribute to the morphological complexity of refugee camps are defined. Eight structural patterns are adopted and assigned under the term morphological features. Secondly, an analysis follows a method that visually categorizes the degree of presence in a morphological feature from low to high based on satellite imagery. The categorization is subsequently verified against a standardized set of metrics, evaluating the stability of structural pattern interpretation recognizable by human vision. For this purpose, the underlying morphological features as subjects of the categorization are reproduced by computation as a representative metric. The derived metrics are calculated using building footprints and camp boundary from OpenStreetMap (OSM) as well as digitized block units. Through visual comparison, statistical analysis and performing an ordinal regression model on the calculated metrics, it is detected that visual categorization is accurately feasible up to three classes. Issues arise for Morphological Features regarding the overall camp structure and path system orientation. Due to inherent variability, especially intermediary classes cause difficulties. Structural contrasts on the other hand could be captured well. Following the evaluation, the results of the categorized morphological patterns are compared using hierarchical clustering. Here, two major group types of refugee sites are identified namely 'planned' and 'organic' refugee camps. While planned ones are defined by pronounced structure such as proper alignment of dwellings and paths, organic camps appear more like a chaotic composition of shelters with a higher degree of heterogeneity. The results further highlight that refugee camps are mostly compact places where dwellings are likely to be small and close to each other resulting in very densely populated living space. However, since there are also deviations from this course, one fact becomes apparent: Refugee sites do not have a rigid physical structure but provide a high diversity in morphology.