The effort to improve sub-standard living conditions in unplanned settlements is often hindered due to a lack of adequate spatial information describing the baseline situation and changes occurring during and after the upgrading process. Low-cost Unmanned Aerial Vehicles (UAVs) could provide very detailed, up-to-date spatial information for small unplanned areas as and when required. To investigate the utility of such platforms in settlement upgrading, UAV flights were conducted over approximately 150 ha of unplanned settlements in the City of Kigali in May and June 2015. Data obtained with UAV were supplemented by an analysis of the spatial information needs of various stakeholders involved in the upgrading project. In the context of the upgrading project, the results of this study identify four main benefits of using UAV imagery. First, it could replace the 2008 25 cm ortho-imagery by up-to-date 3 cm imagery in current workflows for map updating.Second, it enables the extraction of additional information which was previously unavailable, such as detailed elevation data to support surface water runoff analysis and drainage capacity calculations. Third, it speeds up field work and fourth, the imagery provides a foundation for communication between different stakeholders.When using UAVs it is also important to take many practical considerations into account, as well as the societal and ethical context. Results of the first experiences in Kigali indicate that while the use of UAV is not generally perceived as a problem by the local population, fear of forced displacement and expropriation may raise concerns amongst the residents. Communication between the UAV operator, the local government, local leaders and with the residents before and during flights, and sharing the benefits of the acquired information are important to mitigate these fears. Moreover, the resolution and quality of the images is such
I.IntroductionSpatial data is considered essential for unplanned settlement upgrading projects (Kohli et al., 2013, Abbott, 2002Taubenböck and Kraff, 2013). Obtaining an accurate base map of these areas provides a sound basis for Remotely sensed imagery is a key source of spatial information, as it can provide an objective, up-to-date overview of the physical situation in the settlement (Taubenböck and Kraff, 2013). Mason and Fraser (1998) identified seven important roles of satellite imagery for unplanned settlement management: identification of unplanned settlements, identifying changes in the boundaries of these settlements over time, generation of surface data, land use classification, extraction of buildings and other objects for mapping purposes, detailed settlement mapping for spatial modelling purposes, and reconnaissance. However, small buildings and narrow footpaths characteristic of unplanned settlements may hinder the interpretation of commercial satellite imagery with half-meter resolution (e.g. Kuffer et al., 2014).Unmanned Aerial Systems (UAVs) or Remotely Piloted Aircraft Systems (RPAS) also ...