Urban Remote Sensing. Группа авторов

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СКАЧАТЬ 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, the future of UAS in urban remote sensing is promising. Although UAS photography cannot substitute satellite imagery or conventional aerial photos, it does address the need for low‐cost, high‐resolution data being collected quickly and repeatedly. The potential of UAS has been explored in many different areas of urban applications, such as infrastructure inspection, disaster relief efforts, physical disorder detection, and the construction of smart cities. The major challenges faced by UAS missions include legal regulations of air space, logistic planning, safety, privacy, and data protection issues. In particular, there are no universal regulations or standards for the operation of UAS in nonsegregated airspace. Each UAS mission needs to be planned based on the local regulations in terms of the location and mission context. It is necessary to consult relevant departments about the legality of the mission in countries with incomplete institutions for UAS. The required certificates should be obtained before the mission starts. For urban UAS missions, logistic planning can be challenging given the dynamics by nature in urban environments and increased risks of collision with obstacles. Privacy and data protection are also important in the operation of UAS in the civilian sphere. Concerning UAS data quality, post‐processing and evaluation are usually needed to ensure that the products meet the research‐specific accuracy requirements, and GCPs can play a role in improving the product locational and geometric accuracies.

Besides, several technical issues have been identified that can improve the use of UAS in urban areas. Specifically, robust navigation systems should be designed to address the signal occlusion and multi‐path effects caused by urban structures; more intelligent autonomous operation modes will need to be developed to account for the issue of urban obstacles; more sophisticated data processing systems should be developed that can help improve the limited performance of currently small, lightweight platforms; and automated path planning systems are urgently needed. There is still much room for the UAS technology to develop and improve for urban remote sensing. A surge of UAS applications in urban studies can be foreseen when regulations have been developed to better integrate UAS into the general airspace and when technologies have been improved for better UAS urban operations.

REFERENCES

      1 Adam, E., Mutanga, O. and Rugege, D. (2010) Multispectral and hyperspectral remote sensing for identification and mapping of wetland vegetation: a review. Wetlands Ecology and Management, 18(3), 281–296.

      2 Agüera‐Vega, F., Carvajal‐Ramírez, F. and Martínez‐Carricondo, P. (2017) Accuracy of digital surface models and orthophotos derived from unmanned aerial vehicle photogrammetry. Journal of Surveying Engineering, 143(2), 1–10.

      3 Aktas, Y., Ozdemir, U., Dereli, Y. et al. (2016) Rapid prototyping of a fixed‐wing VTOL UAV for design testing. Journal of Intelligent & Robotic Systems, 84 (1–4), 639–664.

      4 Al Shibli, M. (2015) Towards global unification of UAS standardization: regulations, systems, airworthiness, aerospace control, operation, crew licensing and training. International Journal of Unmanned Systems Engineering, 3(2), 32–74.

      5 Alidoost, F. and Arefi, H. (2017) Comparison of UAS‐based photogrammetry software for 3d point cloud generation: a survey over a historical site. ISPRS Annals of Photogrammetry, Remote Sensing & Spatial Information Sciences, 4(4), 55–61.

      6 Aljehani, M. and Inoue, M. (2019) Safe map generation after a disaster, assisted by an unmanned aerial vehicle tracking system. IEEJ Transactions on Electrical and Electronic Engineering, 14(2), 271–282.

      7 Anderson, K. and Gaston, K.J. (2013) Lightweight unmanned aerial vehicles will revolutionize spatial ecology. Frontiers in Ecology and the Environment, 11(3), 138–146.

      8 Ban, Y., Jacob, A. and Gamba, P. (2015) Spaceborne SAR data for global urban mapping at 30 m resolution using a robust urban extractor. ISPRS Journal of Photogrammetry and Remote Sensing, 103, 28–37.

      9 Barbasiewicz, A., Widerski, T. and Daliga, K. (2018) The analysis of СКАЧАТЬ