Following the latest warming phenomenon registered worldwide, cities became the place for the development of urban heat islands, defined as the temperature difference between the urban and suburban areas and the rural areas from their vicinity. It is a concept that is closely linked to urban resilience . Even if it was first examined in the 19th century, we only now have the means to measure them properly and determine the most important factors that contribute to the general effect.
There are certain types of urban heat islands, including ones corresponding to the boundary layer (BLUHI), the canopy layer (CLUHI) and the surface (SUHI). To measure them, there are only three general methods that are successfully used, but until now they were not related with each other. The first one includes the analysis of data registered from different satellite-borne sensors, like LANDSAT ETM, MODIS, SEVIRI and air temperature. The second one regards the local scale, including urban structures. It is based on satellite and ground measurements, in terms of intensity and extensions. The third one concerns point analyses carried out in locations used in the second method and it aims at correlating the analyses of urban heat island impact and energy efficiency of particular buildings. Each one is relevant and defines one type of urban heat island, so we can say that the types and subtypes are related to the observation method and altogether they form an overall measurement vision over the urban area.
The platform for thermal remote sensing shifts between satellite, aircraft and ground-based but each one has its own limitations in terms of characterizing the general UHI phenomenon for a certain case study. Combining the three methods, one can observe the urban climatology from the scale of the entire metropolitan or urban area down to urban details. The air and land surface temperature data can be combined, providing a comprehensive documentation of a certain area. The methods can be also completed by numerical modelling, empirical modelling or scale models. The result is the fourth method, combining all of the three mentioned before.
The results are included in a ruleset that can be consulted by any researcher or research team (at international but especially national level) that examine the urban heat island effect. Therefore, the conclusion of this paper is useful to research teams when planning their work, explaining all the possible method related risks that can occur and establishing the main limitations of the process.