An Analysis of Surface Temperature Changes for Urban Green Space using Unmanned Aerial Vehicles

Background and objective: The urban heat island (UHI) effect is recognized as a representative environmental problem that occurs in cities in summer. This study aimed to quantitatively determine the surface temperature (ST) of UGSs using high-resolution images taken by an unmanned aerial vehicle (UAV), and analyze time-series changes in ST according to spatial characteristics (conifers, deciduous trees, shrubs, grass, metal sculptures, pavements).Methods: In this study, ST data of UGSs were established and acquired through UAV flight and filming, and orthoimages of such data were produced using the Pix4D program. In addition, by comparing RGB orthoimages and green space status data (location of trees and facilities) obtained from field surveys, a green-space type map was prepared using ArcGIS (v10.3.1) software to classify land cover types in green spaces (GSs). ST distribution by GS type was analyzed and statistical significance was verified through one-way ANOVA.Results: As a result, the ST of conifers, deciduous trees, shrubs, and grass, which are vegetation, was found to be lower than that of paved roads: for conifers, 4.1-12.5℃ lower than paved roads; for deciduous trees, 3.0-10.8℃; for shrubs 3.4-11.2℃; and for grass 1.7-8.1℃. In addition, the variations in ST over time were greatest for metal sculptures (28.1℃), followed by pavement (20.4℃), grass (19.4℃), shrubs (14.0℃), conifers (13.3℃), and deciduous trees (13.0℃).Conclusion: Based on the results of this study, it is necessary to consider the components of GS for the efficient planning and management of UGS in terms of improving the urban thermal environment. Insufficient and unsystematic planning and management of UGSs may deteriorate the function of GSs. Therefore, it is necessary to determine and evaluate the ST characteristics of GSs in terms of improving the urban thermal environment.