| Geothermal resources are considered a source of clean renewable energy.The development and utilization of geothermal energy has the advantages of stable heat supply,low cost and high efficiency.Geothermal resources have extensive utilization value and application prospects.With the global attention on the environment and the emergence of the shortage of traditional fossil fuel supply,China is striving to find a clean and renewable new energy source while encouraging the development of hydropower,wind power and solar power generation.The development and application of geothermal resources can solve this problem.In fact,as early as the 1970 s and 1980 s,China began to develop and utilize geothermal energy,but the exploration of underground heat sources is still a limiting factor in the process of geothermal exploitation.The traditional geophysical method is mainly used in conventional geothermal exploration,which is costly,time-consuming,laborious,uncertain,and sometimes even induces geological disasters.Land surface temperature(LST)variations related to heat sources(including secondary heat fields)can be easily measured and mapped using thermal infrared(TIR)radiation sensors.The inversion of LST by TIR satellite remote sensing technology can grasp and analyze these changes in LST macroscopically,which proves to be a macroscopic,fast,convenient and low-cost geothermal detection method.For these reasons,we put forward the research topic of Dandong geothermal resource detection method based on multi-source and multi-temporal TIR remote sensing technology.It took more than three years to carry out the research work of selecting multi-source and multi-temporal remote sensing data,LST inversion based on TIR remote sensing technology and geothermal anomaly extraction,etc.Taking the Dandong area of Liaoning Province as the research area,the LST anomalies in this area were identified via remote sensing,and the geothermal background conditions in this area were preliminarily analyzed in combination with field verification,structural conditions,lithological conditions,and the geothermal storage law in this area was grasped.(1)With respect to temporal selection of TIR remote sensing,a synchronous satellite was used in the research of geothermal detection by multi-temporal TIR remote sensing.Its spatial resolution is very low and it is difficult to detect geothermal anomalies effectively.To improve the accuracy of geothermal detection by remote sensing,multi-source remote sensing detection technology is studied and proposed.Two temporal images of Landsat 8 daytime image and ASTER night-time image with high TIR resolution were selected,which not only meets the requirements of joint analysis of daytime and night-time LST,but also improves the spatial resolution of selected data,and can effectively detect temperature anomalies with in a smaller range.(2)The radiative transfer equation(RTE)in the single channel algorithm and the modified single window algorithm were used to retrieve the LST from daytime Landsat 8 TIRS data,and the two methods were mutually validated.The TES algorithm was used to retrieve the LST from daytime ASTER data,and the inversion accuracy was validated with MOD11A1 LST products in the same period.The accuracy evaluation shows that the accuracy of the LST products of the two temporal LST products meets the research needs.(3)The comparative analysis of two temporal LST products in the study increased the difficulty of identifying the high number of LST anomalies.The spatial-temporal characteristics analysis method was used to analyze the spatial-temporal characteristics of LST of different natural objects and known hot spring points in daytime and night-time,which laid a foundation for the reasonable selection of data dimensionality reduction method and geothermal anomaly detection method.(4)In the delineation of geothermal anomaly areas,in order to eliminate the temperature difference between different natural objects caused by solar radiation,according to the preliminary analysis results,the method of fitting the LST at any time with the diurnal land surface temperature cycle models proposed.Combined with the algebraic operation of the LST in daytime and night-time,not only the high-temperature anomalies were enhanced,but also the relative cold/heat anomalies reflected by the LST between natural objects were effectively eliminated,and the interpretation effect of the geothermal anomaly was improved.And,with converse thinking,the second principal component was used to obtain two temporal LST anomalies.The results show that the high value anomaly in the second principal component has a certain correlation with the existence of geothermal energy,and the two methods confirm each other,indicating that there is a certain LST anomaly in the geothermal area.(5)Due to the existence of known hot springs,the area was developed and the urban heat island effect was enhanced.To eliminate the interference of the heat island on the interpretation of geothermal anomalies,the method of choosing the reasonable sliding window size based on the town scale and the dynamic threshold method were proposed to extract the information of the urban heat island in the study area,which laid a foundation for eliminating the interference of the heat island in the delineation of geothermal anomalies.(6)In order to extract the background value and anomaly value of LST intuitively,conveniently and effectively,based on the statistical analysis of anomaly pixels,the method of "k times standard deviation" was studied and used to determine the reasonable threshold value,thus achieving the purpose of classification,and the identification and delineation of the anomaly areas of LST in the study area was completed.The results showed that after the information of the town heat island in wulongbei and dongtang was eliminated,only the hot spring exposed area was marked as the LST anomaly,and the distribution of the LST thermal anomaly was similar to the hot spring wells,which proved that the marked LST anomaly was related to the existence of hot spring.(7)Combined with the geothermal anomaly areas detected by TIR remote sensing,the geothermal background conditions were analyzed and validated based on the tectonic conditions,lithological conditions,heat source conditions and catchment conditions by using the collected geological and topographic data,and the geothermal storage law in this area was preliminarily grasped.In this study,the multi-source and multi-temporal TIR remote sensing technology was used to detect geothermal anomalies in Dandong area,China.Using the two methods mentioned above,3 geothermal anomaly areas were also found besides 3 known hot springs(Dongtang,Wulongbei,Paoshouying)and 2 urban heat islands(Dandong and Fengcheng)in the delineated geothermal anomaly areas by choosing appropriate thresholds.Through field verification and a comprehensive analysis of geological and topographical conditions,it is preliminarily judged that the other 3 geothermal anomaly areas may be related to the geothermal factors.Preliminary application has achieved good results.Multi-source & multi-temporal thermal infrared remote sensing has proven to be an effective method for delineating geothermal prospects.Compared with mono-temporal LST product,the composite analysis of the land surface temperature of the two temporal LST products is better for geothermal anomaly identification.The research results have certain reference values for the further development and utilization of geothermal resources in this area.In addition,this method has a certain reference value for guiding the rapid detection of geothermal resources in other areas,and has important economic significance and application value for the development and utilization of geothermal resources. |
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