## 4 Conclusions  
In this study, we proposed a method to investigate the effects of the heat load or heat radiation energy from environmental structures on the human body, using three cameras at different wavelength ranges (visible light, near-infrared light, and far-infrared light). To demonstrate the usefulness of the method, the heat load from environmental structures to the human body was measured/determined under different seasons and weather conditions at different urban locations in Tokyo, Japan. The environmental structures were classified into four main categories: sky, plants, ground, and reaming structures such as buildings. The heat load by defining them to have a positive value was evaluated individually from each environmental structure to the human body. The measurements were conducted for the urban environment at three locations in Japan: the Imperial Palace, Ginza, and Daimon, where many people gather. The results of the structure classification showed that the percentage of ground remained almost the same at all locations, while the percentage of structures other than the ground changed. Summer season measurements showed that structures other than the sky at far-infrared wavelengths exert a positive heat load on the human body. Therefore, considering only the far-infrared wavelengths, a larger sky area resulted in a smaller heat load on the human body. On the other hand, a positive heat load was given from the sky to the human body in the visible and near-infrared wavelengths. In addition, the heat load from the ground to the human body varied greatly even if the area of the ground remained unchanged. As the area of the plants increased, the radiation to the ground was shielded, and the heat load from the ground to the human body decreased. However, as the area of the buildings increased, the heat load from the ground also increased. Winter season measurements showed that the heat load became negative for all structures in the far-infrared wavelengths. On the other hand, all heat loads were smaller at visible and near-infrared wavelengths because the flux of sunlight reaching the ground surface was smaller. Therefore, the negative heat load in the far-infrared was dominant in winter, and the visible and near-infrared radiation had little effect on the heat load to the human body. Cloudy weather measurements showed that the heat load from the ground at visible and near-infrared wavelengths almost disappeared, and the heat load from the sky became dominant. Due to the cloudy weather and the seasonal difference from the summer experiment, the temperature of all structures was lower than that of the human body, and they showed negative heat loads in the far-infrared wavelengths, as in winter. These results indicate that the heat load on the human body due to radiation at visible, near-infrared, and infrared wavelengths varies in a complex manner depending on the proportion of city structures and variations from season and weather. In this experiment, characteristic locations in Tokyo, Japan were chosen, but measurements can be realized, in fact, by extending the proposed method to a wider variety of environments over different countries. We believe the findings reported in this paper could have implications when considering the countermeasures against UHI. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app122010412/s1](https://www.mdpi.com/article/10.3390/app122010412/s1)]([https://www.mdpi.com/article/10.3390/app122010412/s1](https://www.mdpi.com/article/10.3390/app122010412/s1)), Figure S1: Example of a measured image using standard diffuse reflector taken by a visible light camera, where the red area is obtained as the average value; Figure S2: Schematic diagram of measurement using a camera attached with a rotation unit; Table S1: Specifications and the number of pixels used in the calibration experiments for each camera. Conceptualization, T.K. and J.Y. ; methodology, T.K., J.Y. and U.M.R. ; software, T.K. and Y.N. ; validation, T.K. and Y.N.