| With the continuous progress of society,the traditional energy is increasingly exhausted,and the task of finding reliable,stable and green energy is imminent.As an important mineral resource,geothermal resources have many advantages such as green environmental protection,wide distribution,renewable,non-polluting the environment and stable and reliable utilization.The development and utilization of geothermal resources has become a research hotspot.The use of remote sensing technology for the general survey and exploration of geothermal resources has many advantages,such as shortening the exploration cycle,reducing the exploration cost,and improving the exploration efficiency.Although the use of remote sensing technology can make up for the shortcomings of traditional exploration methods,there will be errors only in the geothermal anomalies delineated by remote sensing,so it is necessary to remove the false and seek the truth of the retrieved geothermal anomalies.The main research methods and contents are as follows:Taking Lhasa City as the main research area,the atmospheric correction method was finally selected to retrieve the surface temperature from Landsat8 remote sensing images by comparing and analyzing the atmospheric correction method,single-channel algorithm,single-window algorithm and split-window algorithm.In addition,the reverse surface temperature and MOD11A2 surface temperature products are analyzed and compared,and the temperature change trend of the two is basically the same,and the temperature difference is small,which proves that the surface temperature retrieved based on Landsat8 data has high reliability,and the resolution of the surface temperature retrieved based on Landsat8 is high.In order to more accurately delineate geothermal anomaly points,a new geothermal anomaly determination factor,surface evapotranspiration,is introduced.The SEBAL model is selected for the inversion of surface evapotranspiration.The model has the advantages of clear concept,clear mechanism,less input parameters of the model,simple data acquisition,high inversion accuracy and wide application range.Firstly,the surface parameters such as NDVI,surface emissivity and surface albedo should be calculated,and the surface net radiation flux,soil heat flux,sensible heat flux and latent heat flux should be inverted,and the inverted instantaneous evapotranspiration should be expanded into daily evapotranspiration by combining evaporation ratio method.The measured data and the P-M formula are used to verify the evapotranspiration of the SEBAL model,which proves its credibility,and analyzes the spatiotemporal distribution characteristics of evapotranspiration in Lhasa.After the inversion of surface temperature and evapotranspiration,the inversion results need to be statistically analyzed to extract geothermal anomalies and evapotranspiration anomalies.First,based on the global threshold method,the threshold of the whole research area is extracted,and the extracted thermal anomaly is used as the primary selection result.Secondly,the study area is divided into 68sub-regions based on the local block threshold method,and the geothermal anomalies of each sub-region are extracted respectively.The geothermal anomalies are roughly distributed in the valley dew split zone,Nimu County and the central area of Lhasa City.Then,combined with the analysis of the fault zone structure,10 geothermal anomaly areas are delineated in the study area.The evapotranspiration anomaly is further extracted in the delineated geothermal anomaly area to make the geothermal mapping result more accurate. |
