Multi-source Remote Sensing Inversion Method Of Soil Water Content Over Agriculture Fields

Soil moisture content is an important parameter of water balance,which has essential actors during hydrology,climate and ecology research.Soil moisture content is the key source of water resources for vegetation,regional scale of surface soil moisture content acquisition has been the focus of the research on soil water.There are many retrieval methods of soil moisture content,but all of them are based on point measurements,substituting point for surface,which is hard to realize rapid monitoring of soil moisture content in large area.The drastical development of remote sensing,perfectly solve the difficult problem of soil moisture content dynamically and real-time monitoring What's more,microwave remote sensing is widely used in soil moisture retrieval with its all-weather,all-day,certain penetration capacity on the surface.The paper uses the C band Radarsat-2 radar data combining with study area measured data,to analyze the application of experience model study area,optimal semi empirical model of the study area,Which provided a new method for improving the soil moisture content inversion accuracy over bare fields.Based on the systematic analysis the influence of radar system parameters,the surface parameters on backscattering coefficient,and based on the IEM model,effectively combine texture status of the study area,and consider pixel as calculated unit,build up a relationship model between surface temperature(main sensitive factor)and soil dielectric constant at different locations and construct soil moisture content inversion semi-empirical model over bare fields,upgrade the points which absolute error within 0.06 between measured and inversion soil moisture content from 43% to 78%,greatly improve the accuracy of the inversion,when combined the soil types of different region,which can effectively enhance the applicability of the new method,the applicability of this method to different region was significantly improved.In order to eliminate the effect of maize canopy on soil moisture content,this paper is based on PROSAIL radiation transmission model,combining OLI remote data and measured maize canopy moisture content,and screen optimum index of maize canopy moisture content inversion,construct the maize canopy moisture content inversion model in different growth stages,and establish the table lookup table of canopy water inversion model for no real-time maize canopy water.The four parameters "water cloud” model,this paper constructed,is suitable for the soil moisture retrieval over thick maize fields,the inversion accuracy of the four parameters " water cloud” model is comparable with conventional "water cloud” model,but the four parameters " water cloud” model is leaner and cleaner,and easy to realize soil moisture inversion programmed operation and automatic monitoring,which authenticates the usability of the new method;Using C band active microwave data,aiming at the improved ratio model,develop innovative research of soil moisture retrieval,which is seldom involved in home and abroad over the thick maize fields,realize soil moisture content inversion over dense maize fields,which verifies the feasibility of C band radar for soil moisture content inversion over dense corn fields.Based on the method this paper improved,combining with the remote sensing data and measured data of the study area,making bare surface soil moisture content distribution thematic maps,bare maize fields surface soil moisture content distribution thematic maps,which can provide basic data for many departments,such as agriculture,water conservancy and so on.