# Identification of Industrial Heat Source Production Areas Based on SDGSAT-1 Thermal Infrared Imager
## 2 Materials and Methods
### Method
#### 2.3.1 Data Prepossessing  
Radiometric calibration is a critical step in remote sensing data processing that involves converting raw radiation values received by sensors into precise and comparable measures of the surface reflectance or radiant brightness [39]. This transformation is essential for ensuring data accuracy and consistency across different acquisitions [40]. Because the unprocessed SDGSAT-1 TIS data contain only digital numbers (DNs), radiometric calibration is needed. In this paper, post-launch calibration based on parameters taken from the data file was used to transform the SDGSAT-1 TIS data. The spectral radiance was calculated by the following formula:  
\[\text{L}_{\text{i}}=\text{DN}_{\text{i}}\times\text{GAIN}_{\text{i}}+\text{ BIAS}_{\text{i}} \tag{1}\]  
where \(\text{DN}_{\text{i}}\) is the pixel value of the ith band, and i (set in {1,2,3}), as shown in Table 1, represents the band identification number of the SDGSAT-1 TIS. \(\text{GAIN}_{\text{i}}\) and \(\text{BIAS}_{\text{i}}\) are the calibration gain and offset values, respectively. They can be obtained from the corresponding \"*.calib.xml\" file. In this context, the values of the radiation calibration parameters can be seen in Table 2. \(\text{L}_{\text{i}}\) is the spectral radiance value.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Dataset Name** & **Producer** & **Period** & **Resolution** & **Website** \\ \hline SDGSAT-1 TIS product & CBAS & 15 June 2022 & 30 m & [[http://124.16.184.48:6008](http://124.16.184.48:6008)]([http://124.16.184.48:6008](http://124.16.184.48:6008)) (accessed on 27 August 2022) \\ \hline Landsat-8 OLI product & USGS and NASA & 16 June 2022 & 30 m & [[https://www.usgs.gov](https://www.usgs.gov)]([https://www.usgs.gov](https://www.usgs.gov)) (accessed on 26 August 2022) \\ \hline High-resolution optical images & DigitalGlobe, EarthSat, etc. & / & 0.5 m & Google Earth ([[https://www.google.cn](https://www.google.cn)]([https://www.google.cn](https://www.google.cn)), (accessed on 22 August 2022)) \\ \hline IHS datasets & [PERSON]’s datasets & [PERSON]’s team & 2018 & Polygon & [[https://doi.org/10.1016/j.rse.2017.10.019](https://doi.org/10.1016/j.rse.2017.10.019)]([https://doi.org/10.1016/j.rse.2017.10.019](https://doi.org/10.1016/j.rse.2017.10.019)) (accessed on 9 October 2022) \\ \cline{2-5}  & [PERSON]’s datasets & [PERSON]’s team & 2018 & Polygon & [[https://doi.org/10.3390/su10124419](https://doi.org/10.3390/su10124419)]([https://doi.org/10.3390/su10124419](https://doi.org/10.3390/su10124419)) (accessed on 7 September 2022) \\ \hline Administrative divisions &
\begin{tabular}{c} National Centre for \\ Basic Geographic \\ Information \\ \end{tabular} & 2020 & Polygon & [[https://www.webmap.cn](https://www.webmap.cn)]([https://www.webmap.cn](https://www.webmap.cn)) (accessed on 18 September 2022) \\ \hline \end{tabular}
\end{table}
Table 1: The information on the data used in this paper. The CBAS refers to the International Research Center of Big Data for Sustainable Development Goals.  
\begin{table}
\begin{tabular}{c c c} \hline
**Band (Band Center (\(\mu\)m))** & **GAIN** & **BIAS** \\ \hline Band 1 (9.35) & 0.003784 & 0.163435 \\ Band 2 (10.73) & 0.003901 & 0.125908 \\ Band 3 (11.72) & 0.005159 & 0.205793 \\ \hline \end{tabular}
\end{table}
Table 2: Values of radiation calibration parameters on SDGSAT-1 TIS. The spectral radiance value of each TIS band can be calculated by the GAIN and BIAS values based on Equation (1).  
Landsat-8 Level-2 products are generated by applying additional corrections to Level-1 products to remove spatially, temporally, and especially variable atmospheric effects. In the absence of atmospheric scattering or absorption effects, the Level-2 data provide estimates of the target surface reflectance as determined in situ [41]. To obtain the actual value of Landsat-8 Collection-2 Level-2 data, the reflectance data need to be multiplied by a scaling factor of 0.0000275 and added to a constant of \(-0.2\)[42].