**3. Material and Methods**

This paper employs a mixed methods approach including qualitative and quantitative data to assess the potential of UAS-technology to meet land administration requirements in developing countries. The research framework addresses both the social/institutional as well as the spatial/technical perspective (Figure 1). On the one hand, land information needs of various stakeholder groups are identified through a needs assessment process. On the other hand, case studies of multiple test flights provide input to evaluate the institutional environment and data quality of UAS-based orthoimages. Results are synthesized and jointly discussed to give a better understanding of UAS-technology as a fit-for-purpose tool in the context of land administration [21] and how policies can build on this.

**Figure 1.** Conceptual framework of the multi-disciplinary approach.

#### *3.1. Needs Assessment*

Land information needs assessment for Rwanda was conducted using a form of group interview known as the Nominal Group Technique (NGT). NGT was selected as it facilitates a balanced input from all participants, taking advantage of individuals' knowledge and experience to provide deep and meaningful results ranked by importance to the topic of interest [30]. NGT is an effective approach when an identified problem requires a group's ideas and evaluation and therefore well-suited for conducting a needs assessment [31–33]. During the session, only one to two questions are posed to the group as each question takes around two hours to complete. A response to the question in terms of ideas are generated individually then gathered and combined as a group. Group consensus is reached through two rounds of individual voting, a process which prioritizes ideas and provides insight into the extent individual participants agree or disagree with the consensus vote. This structured process has been proven to be effective in addressing power imbalances or dominant behaviour in group data collection like some participants being more vocal than others [34–36].

Validity in the method is accounted for by recruiting participants who are considered experts on the topic [37]. Hence participants were identified by local land administration experts using purposive and snowball sampling. Thirty-eight *organizations* were contacted; of these, 22 participated (58% response rate). Three workshops were held at local and national levels. Invited organisations included national and local (district, sector and cell levels) public sector organisations associated with land (e.g., planning, housing, registration, infrastructure, development), non-statutory organisations, private sector organisations (e.g., leading geospatial consultancies), and several universities (Table 1). Invitations were sent to senior executives within organizations and it was left to the organization to send the most appropriate representative to the workshops. For national workshops, attending participants tended to be middle- or senior-level managers; at the local level, attending participants tended to be frontline operational staff.

At each workshop, one nominal question was posed (due to time limitations): "What land tenure and land-related information are still needed for sustainable *urbanization*?". This was followed by a discussion on how UAS might meet these needs. Cell (smallest administrative entity in Rwanda) officials who could not attend the workshops were interviewed individually using an adapted version of the NGT. Data collection ceased after six interviews when no significantly different insights were gained after four interviews.


**Table 1.** Types of stakeholders participating in data collection workshops.

#### *3.2. UAS Data Collection*

In general, the UAS-based data acquisition workflow includes both technical and non-technical aspects. As shown in Figure 2, the UAS itself, the UAS pilots as well as the legal permission to conduct UAS flights refer to the main requirements to proceed with the data acquisition. In this research investigation, the UAS data collection aimed to provide an accurate orthophoto of the study area. Flight planning, data acquisition, and data processing were executed accordingly.

**Figure 2.** Unmanned Aerial Systems (UAS) data collection–requirements and data acquisition workflow. (**a**) UAS equipment, payload and the ground control station; (**b**) trained staff to pilot and operate the UAS; (**c**) legal permission to conduct the UAS flight mission which can set its own requirements according to the national jurisdiction; (**d**) flight planning with an appropriate software and definition of flight characteristics; (**e**) acquisition of UAS images in the area of interest; (**f**) data cleansing and photogrammetric processing including quality assessment.

#### 3.2.1. UAS Regulations in Rwanda

UAS related regulations are a vital requirement in the safe and successful use of UAS technology. In May 2016, the Ministerial Regulations N◦01/MOS/Trans/016 relating to the use of UAS in Rwanda were officially gazetted [38]. Respective regulations are very prescriptive and contain subparts dealing with UAS registration and marking, privacy and safety, airworthiness certification, operating rules and pilot licensing [14]. Before any commencement of activities, the UAS needs to be registered and marked with a unique identifier. Furthermore, pilots, as well as operating agencies, need to hold specific licenses issued by Rwanda Civil Aviation Authority. These requirements demand a high standard

of UAS professionality and make it a challenge for external companies and institutions to obtain legal flight permissions. At the time of writing, the authors were yet to complete the administrative procedure required (despite commencing the process in 2017) to operate UAS in Rwanda. Therefore all data collection flights were carried out by Charis UAS Ltd., a Rwandan company specialized in UAS services and the first UAS certified company in Rwanda. The experiences of the authors with the UAS regulations and respective governmental institutions point at very high institutional barriers for market entry. There is only one company which is a certified UAS operator (for land-related mapping) and arguably has a monopoly position. For the specific case related to the work at hand, processes were not transparent and slow with limited access and availability of authoritative, unambiguous and assured information. Although UAS regulations are in place, gaps and lack of capacity can be seen when it comes to both enforcement and implementation.

Besides requirements towards pilot certification, UAS registration, and operator certification, Rwandan UAS regulations outline several operational limitations that have to be taken into account during all UAS flight missions (Table 2). In general, most specifications reflect common restrictions [39] except for the lateral distance between the pilot and the UAS. Even though the visual line of sight remains undefined, the maximum lateral distance of the pilot to the UAS in operation was set to 300 m in 2016. This imposed a substantial constraint to UAS mapping projects. However, in the course of 2018, UAS regulations were revised, and the maximum lateral distance disappeared from the restrictions and the flight height was lifted to 120 m [40]. Specifications of restricted areas and requirements towards distances to structures and people are comparable to standard practice.


**Table 2.** Operational limitations for UAS flight missions in Rwanda according to Rwandan regulations [38,40].
