## 2 UAV Platform Evolution
### Multispectral Sensors
Hyperspectral sensor developers, such as Headwall Photonics, specialize in small, rugged hyperspectral systems viable for UAV platforms, as illustrated in Figure 6. Integrating hyperspectral imaging into standard UAV electro-optical and infrared sensor suites poses engineering challenges; however, recent advances have made high-resolution UAV-based hyperspectral analysis achievable. This allows exploiting hyperspectral data's detailed spectral signatures for UAV remote sensing tasks. Compared to the multispectral data, hyperspectral data offers a superior identification and discrimination of targets due to the narrow bandwidth information acquisition. The key benefits of hyperspectral data are the capacity for precise spectral signature detection and monitoring; however, effective utilization requires determining the most informative bands for discriminating specific features while minimizing the redundant data. Careful hyperspectral sensor selection, calibration, and data processing allow realizing the benefits of rich spectral information for target identification and change detection. Within the built  
Figure 5: Comparison between standard multispectral UAV sensors, resolution, costs, and compatibility [70; 85; 86; 87; 88; 89]. environment, high-spectral resolution facilitates identifying specific materials through absorption features and mapping of urban composition, including vegetation type, water quality, and infrastructure materials [92]. Hyperspectral sensors also help construct 3D models distinguishing building materials for assessing energy efficiency opportunities [93], where roof type and insulation defects prone to energy deficiencies can become more apparent. Meteorological sensors for UAVs encompass a range of technical specifications that enable the collection of crucial weather data. These sensors typically include instruments for measuring parameters, such as air temperature, relative humidity, atmospheric pressure, wind speed, and wind direction [98]. The accuracy and precision of these measurements are essential for understanding the dynamics of the atmosphere and its interactions with the environment. Common meteorological UAV sensors include miniaturized air temperature, humidity, barometric pressure, wind speed, and direction sensors that weigh as little as 25 grams [66]. UAVs facilitate sampling at low altitudes versus traditional weather balloons or weather stations that are relatively remote from the urban layer [99]. This enables the detailed measurement of near-surface urban heat islands, air pollution layers, and urban microclimates. For example, UAVs equipped with thermometers, hygrometers, and anemometers can monitor outdoor thermal comfort levels and help identify the areas needing improved ventilation at the neighborhood level [4]. Furthermore, meteorological sensors on UAVs can contribute to assessing air-quality and pollution levels in urban areas. By measuring parameters, such as particulate matter, carbon dioxide, and other pollutants, these sensors provide valuable data for understanding the impacts of climate change on air quality and human health [100]. Moreover, UAVs with meteorological sensors can profile vertical air temperature and humidity stratifications along building facades to optimize passive cooling and ventilation. UAVs can also carry a range of miniature chemical sensors to detect gases, particulates, and environmental pollutants. Gas sensors, such as metal oxide semiconductors and electrochemical and infrared spectrometers, enable UAVs to identify and map concentrations  
Figure 6: Different hyperspectral sensors and their spatial and spectral resolutions [90; 94; 95; 96; 97]. of CO, CO2, SO2, NO2, and more [66]. Particulate matter sensors using laser scattering or embedded quartz crystal microbalances can measure PM2.5 and PM10 levels [101]. UAV flexibility allows the targeted sampling and gradient mapping of industrial emission plumes, volcanic outgassing, and air pollution, even in hazardous settings [12].