4.3.2. Provision of up-to-Date Data

A comparison of the obtained UAS-based orthomosaic of Muhoza and the corresponding orthomosaic which is based on classical aerial photos from 2009 shows a high number of clearly visible changes (Figure 7), where 13 large buildings and 28 small buildings/annexes were newly constructed, 5 buildings were demolished, and 28 large buildings and 10 small buildings/annexes remained. Especially urban and peri-urban areas face numerous changes with regard to development and urbanization. The high level of detail and the immediate availability of aerial photos provide the geospatial basis to extract up-to-date land use, land development, and topographic information of small scale areas which is crucial to implement current urban development plans efficiently. Similarly, the timely provision of UAS data could support the delineation of parcel boundaries based on orthomosaics or regular base map updating activities. Especially up-to-date 3D point cloud data obtained from UAS images was identified as input for 3D cadastre. A data type, which can neither be provided by satellite images nor by aerial images.

**Figure 7.** Left: Orthomosaic based on aerial images from 2009; centre: Orthomosaic based on UAS images from 2018; right: Change detection of buildings (orange: buildings remained the same, red: buildings got demolished, blue: new building constructions).

A low significant contribution of UAS data can be seen in contributing to a multi-purpose spatial data infrastructure which enables the integration of different data, which can further support the implementation of spatial development plans. In general, UAS-based data acquisition workflows allow stakeholders to gradually upgrade existing base-maps at a small scale, without the need for significant financial outlay upfront–two fundamental aspects of fit-for-purpose approaches.
