*5.1. Opportunities of UAS Data Collection to Match Land Information Needs*

The socio-technical assessment revealed that the technical capabilities of UAS-based data are well-placed to match most of the prioritised needs in Rwanda. These needs did not only reflect the type of data (e.g., land use data, geological data, utility supply data, etc.) but also on characteristics of data and processes (e.g., geometric accuracy, spatial resolution, custodian of data, data integration, accessibility, etc.). This enabled the matching of the characteristics of UAS data to a particular type of data as well as the specific requirements of the data such as temporal resolution or geometric accuracy. The synthesis as shown in Figure 6 demonstrates that there is a high number of needs where UAS data could potentially have a significant contribution. The results suggest that UAS as a data acquisition device could most likely be adopted by national-level stakeholders or sub-national government stakeholders, which can be attributed to the system in Rwanda where the national government is the main provider of geospatial data. However, with UAS as a low-cost and flexible data acquisition

platform, sub-national or local government stakeholders could increase their share of data provision, especially with regard to small scale mapping or multi-temporal flight missions in a local context. This would facilitate the co-production of land information in a decentralized way, a finding that is also reflected by [19]. The opportunity of using UAS-based images to delineate or enhance the accuracy of parcel boundaries is in line with the guiding principles for building fit-for-purpose land administration systems in developing countries [46]. Here, UAS were specifically outlined to provide the large scale image maps to map spatial units in densely populated areas (urban central, informal settlements and small towns). Results further suggest that UAS data can fulfil multiple needs across different domains such as planning and surveying. This is contrary to conventional ground surveying with GNSS or total station, where acquired data only serves a single purpose. Although not explicitly prioritised as a need, the UAS test flights showed that the (nearly) immediate availability of orthophotos could promote citizen participation in the adjudication process, a critical result which was also outlined by [19,47]. Even though the Rwandan land administration information system is very advanced in comparison to other African countries, it was found that the digital nature of a generated UAS-based orthomosaic can easily be integrated in existing spatial data infrastructures to be used by numerous GIS applications, or if absent, support the modernization of current paper-based land registration systems.

#### *5.2. Challenges of UAS Data Collection to Match Land Information Needs*

Aside from those advantages, the UAS test flights in Rwanda also reveal four main challenges with regard to the implementation of UAS as a data acquisition tool to match land information needs.

Firstly, it needs to be noted that the terrain in Rwanda–the country of the thousand hills–is a very challenging testbed. Fixed wing drones have only limited climbing rates, and flight planning must be aligned with the physical environment. The availability of sufficient open space for appropriate landing strips is an essential precondition which was found to be challenging to fulfil. Hybrid UAS and rotary wing UAS are likely a more suitable instrument for small scale mapping activities. Current limitations with regard to battery capacity and flight time make hybrid UAS more effective for mapping tasks as they have aFRTK better flight endurance. In contrast, rotary wing UAS should be preferred to monitor the operation of utilities.

The second hurdle refers to the UAS regulations in Rwanda. With an operational limitation to fly only in visual line of sight, scaled application of UAS-mapping activities remain aspirational. Acknowledging the plans of the Government of Rwanda, legislation with a more performance-based orientation may soon be drafted and implemented more effectively. This development could pave the way for broader use of UAS-based data acquisition that supports land tenure recording, as well as extensive land information collection for development purposes, as envisaged in [48].

The third hurdle includes the topic of ground truthing. It has been shown that especially in an urban environment, the collection and measurement of reference points are challenging and means of ground marking should be context-specific. PPK and RTK capable UAS can provide an answer to this challenge as they minimise or even eliminate the need for ground control measurements. However, the availability of professional GNSS equipment or a national network of existing GNSS reference stations is an essential precondition for RTK or PPK-based workflows. If the national CORS is not reliable or not existing, other means of accurate GNSS measurements such as Precise Point Positioning should be taken into consideration.

The fourth challenge refers to soft- and hardware requirements for data processing. Experiences of the authors in Rwanda revealed that the majority of employees of the Rwanda Land Management and Use Authority have a machine which could be able to process smaller datasets up to 500 images. However, to facilitate the processing of the data of an entire township, machines with more RAM and disk space would be needed–ideally a server environment. Cloud-based processing is seen very critical, as internet connections are very often subject to outages. Financial barriers to purchase the required hardware and a commercial software such as Pix4D or similar were perceived as very high–costs that are likely to exceed the procurement costs of the UAS equipment. At the same time, current open

source software cannot reproduce the same data quality as commercially available software. However, given the rapid development of Open Drone Map, and the increasing number of users, the software algorithm is likely to mature in the close future.
