As part of our research and development activities, we equipped one of our drones with a thermal radiometric camera and flew over an urban area featuring a wide variety of different surface materials (asphalt, cement, metal, glass, soil, foliage, etc.). Our goal was to study the thermal footprint of different surfaces and its change during the day cycle. Flights were held from 8:00 in the morning to 20:00 at night with a time step of 2 hours. Following is a brief animation with the alternation of thermal orthophotos every 2 hours, where one can observe how the surface temperature of the different materials changes during the day. The color gradient follows the rule, blue: cold – yellow: warm, while each pixel represents the surface temperature of the corresponding material.
Most materials feature a maximum surface temperature at 14:00, however they behave differently both in absolute temperature and in its rate of change. A typical example is the thermal behavior of asphalt surface, where while its initial temperature is equal to the average temperature value of the other different surfaces (22 o C), it still maintains high temperature values for a longer period during the day than the rest of the materials.