Urban Remote Sensing. Группа авторов
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are conducted. The rapid development of UAS technology in recent years has led to a present regulatory challenge facing government officials. How do we allow UAS technology to become an integral tool in a wide variety of industries while also not creating new problems related to the increased presence of UAS in civil airspace? Different countries/states/provinces/regions have UAS regulations that are often structured with similar intentions, especially if they are regional neighbors. However, there is still a wide discrepancy in the specific details of these regulations from one regulatory body to another. Although the specific details of one country’s UAS regulations may differ from the rest, there are many common topics that the regulations are focused on. These regulatory topics generally include restrictions on flight altitude, max UAS speed during flight, which airspaces UAS can be operated within, design limitations of UAS platforms, and other potential risks posed to the public (Al Shibli, 2015). The use of UAS in civil airspace presents a host of potential risks and problems, such as surveillance and privacy concerns (West and Bowman, 2016), noise disturbances to the public (Wallace et al., 2018), and the general lack of universally standardized safety features in contemporary UAS models (Plioutsias et al., 2018). For these reasons, it is highly advised for UAS operators to look at the regulations from the specific country before conducting any aerial operations.
In the United States, the Federal Aviation Administration (FAA) regulates all UAS operations under Part 107 of Title 14 of the Code of Federal Regulations. The UAS‐specific part, “Part 107,” was announced in July 2016 and serves as the regulatory framework structuring hobbyist and commercial operations for all UAS flown in the US General information on Part 107 regulatory framework and UAS operations can be found at the FAA’s public website, www.faa.gov/uas. Part 107 generally allows for UAS operations to be conducted if the UAS is under 55 pounds, at or below 400 ft AGL, and always within the visual line‐of‐sight. There are many more rules included in the Part 107 framework, such as limitations on operations in particular airspaces, limitations on operations over people, visibility requirements, commercial pilot certification requirements, and the waiver process (14 C.F.R. § 107, 2020). With the expansion of UAS platforms for not only hobbyists but also commercial purposes, there is a litany of new safety issues that the FAA has not had to regulate in prior decades until now. Lower altitude operations by UA pose new risks to the national airspace and terrestrial environment alike, ranging from physical risks of collisions with ground structures or manned aircraft (Ramasamy et al., 2016), to challenges with regulatory compliance by UAS operators (Morris and Thurston, 2015). Some regulations crafted in an attempt to uphold safety during UAS operations have inadvertently led to significant constraints on the feasibility of particular UAS applications. The best example of this is how the regulations impact the feasibility of urban remote sensing applications with UAS in the US Limitations on flights over people, critical infrastructure, and traffic make it effectively impossible to conduct any autonomous operations with a UAS in dense urban areas. As Card (2018) noted, these regulations are increasingly prohibitive to not only hobbyists and research purposes but also to the integration of UAS into commercial industries. Although the FAA’s current Part 107 regulations support safe operations with UAS, they do create limitations on the types of industries that can make use of this technology inadvertently. According to Wallace et al. (2018), this regulatory trend is also not limited to only the United States, and there are many other countries around the world that are facing the same regulatory challenges with the integration of this technology.
3.6.2 OPERATIONAL CHALLENGES
Operationally, accomplishing a UAS mission is no simple task. Implementing UAS missions in urban areas with intensive human activities takes efforts to address a host of issues, such as legal, safety, ethical procurement and partnerships, privacy and data protection, data transparency, informed consent, and community engagement for humanitarian purposes (Gilman, 2014). Major safety hazards of using UAS in urban areas may include bird strikes, collisions with other aircraft, and/or impacts with people or structures on the ground. Large structures like skyscrapers or transmission towers can impede the communication between the aircraft and the GCS, diminishing navigational performance by shielding the UAS from GPS satellites and increasing multipath reflection (Clothier and Walker, 2015). Low‐altitude UAS operations can be even more challenging under the presence of obstacles like trees, slopes, towers, and powerlines. Therefore, there is a need for UAS manufacturers to enrich the pool of obstacles that the safe autonomous mode can recognize and avoid in‐flight (Ippolito et al., 2016).
UAS can also cause a higher noise floor and unintentional jamming in an urban area (Watkins et al., 2020). In some countries, such as the United States, there are significant concerns from the public regarding personal privacy and one’s reasonable expectation of it. Therefore, legal and ethical issues need to be addressed in any UAS mission, especially those operating in higher risk areas, such as urban areas (Skrzypietz, 2012). Therefore, a proficient crew of knowledgeable personnel is always essential for the deployment of UAS in a safe, legal, and ethical manner. The skillsets for the UAS team to ensure safe operations generally include (but are not limited to) a strong understanding of situational awareness, proper assignment of roles, recognition of UAS pilot fatigue, the use of a risk mitigation procedure, knowledge of UAS and all related components, and effective communication with all other crew members.
Another important factor related to operational challenges is the necessity of good logistical planning for UAS missions. Good logistic planning is integral to any successful UAS mission, but it also takes a lot of input from the operators to ensure success. A good logistics plan should include mission‐specific information for the pilot, preparation of spare equipment and upkeep of regular maintenance, and plans for comprehensive operational support from other crew members. To make sure the UAS platform’s flight endurance is long enough to cover the study area, the size of on‐board storage and power to support data transmission should be considered in all mission planning. In case of unexpected situations, spare parts and repair tools are always needed. At least two sets of UAS are needed, so are other parts like propellers, landing gears, batteries, antennas, etc. It is also better to bring an extra number of pilots if possible. In terms of operational support, every aspect of the trip must be considered, including transportation, housing, safety and security, information technology, telecommunications, and power and infrastructure. In terms of safety and security, the team should be aware of local medical assistance and travel vaccinations. Information technology includes functioning computers, software, and supplies like converters and chargers to support data storage, indexing, and management. Telecommunications deal with how crew members communicate with each other and the local coverage of cellular data. Power and infrastructure concerns include local outlet type, the voltage, the accessibility of the mission site, and the requirements on vehicles.
3.6.3 SPATIAL COVERAGE AND DATA QUALITY
Despite that a UAS supports the collection of high‐resolution imagery with elevation information, it is hard to cover a large mapping region given the limited battery life and the number of batteries that can be carried by the crew. Particularly, the FAA restricts the number of spare lithium‐ion and lithium metal batteries each passenger can carry on a flight (Federal Aviation Administration, 2013), which should be considered when air travel is necessary to complete a UAS mission. The quality of UAS products is another important consideration in research studies. Unlike conventional aerial photography or space imaging technology, UAS mapping is achieved through photogrammetrical methods building a model that defines the spatial relationships within the images and then stitches them together. Post‐processing is usually needed to make sure the UAS products meet the research‐specific requirements on geometric accuracy, radiometric accuracy, spatial extent, spatial resolution, temporal resolution, etc. Using control points is an effective way to enhance the geometric correction of the UAS imagery. It has been found that the horizontal and vertical accuracy of UAS photogrammetry results can be narrowed down to centimeter‐level with certain amounts of GCPs (Devriendt and Bonne, 2014). With accurate locational data, reliable DEM products can be derived from UAS point clouds through classification (Day et al., 2016).
3.7 SUMMARY AND OUTLOOK
Overall,