Terrain Radiation Correction Based On ALOS PALSAR Data

Synthetic Aperture Radar(SAR)is an active earth observation system with all-weather,all-day,high-resolution,multi-band,multi-polarization,and variable side viewing angles.SAR is widely used in agricultural production,military reconnaissance,scientific research and aviation measurement.In particular,with the maturing of carrier platform technologies such as spaceborne,airborne,and unmanned aerial vehicles,SAR data products have been widely used in various fields,such as resource investigations,military aspects,geological disasters,oceanography,and hydrology in mountainous regions.However,in the rugged mountainous areas,due to changes in the terrain,the echoes of the ground received by each pixel in the corresponding SAR imaging are very different,so that both the geometric and radiation characteristics are affected,which hinders the SAR imagery that comprehensive application of feature information extraction and other aspects of information.Therefore,the research of SAR image topography radiation correction is not only a hot issue in the field of microwave remote sensing,but also has an extremely important significance in information extraction,interpretation,quantitative analysis and parameter inversion.In order to make full use of SAR imagery in various fields and to exert its own application value,this paper has studied in-depth the R-D positioning model,based on the optimization technology of orbital satellite parameters,and optimized the imaging parameters to study and analyze SAR images techniques and methods for orthorectification and terrain radiation correction.This paper analyzes the theory of SAR imaging and the geometric features and radiation characteristics of SAR images.Based on this theory,the parameters of the R-D model solution are extracted from the metadata,and the polynomial orbit description method and the four-parameter method of orbital number description are introduced.The method is used to fit the satellite orbits,and the practicality and accuracy of the two methods are compared and evaluated.Based on the satellite orbit description,the R-D positioning model is constructed,and the indirect positioning method and the direct positioning method are discussed in detail based on the optimized orbit parameters.Then by establishing a SAR positioning model,combining the DEM image coordinate position,solving the calculation function,the grayscale value of the simulated image is determined to generate a SAR simulated image.The orthorectified SAR image and the original SAR image are automatically matched for orthorectification,and the validity of the correction result and the positioning accuracy are analyzed and evaluated.The results show that the orthorectified SAR image positioning accuracy is compared with the actual field data,and the positioning accuracy is significantly improved.Since the orthorectification does not eliminate the influence of terrain on SAR images,this paper based on the orthorectification,based on the local incidence angle calculation method and the projection angle calculation method respectively performs SAR correction on the SAR image,and through quantitative and qualitative the index performed the accuracy evaluation and experimental analysis of the calibration results.The calibration results show that the SAR image corrected by terrain radiation can effectively eliminate the terrain effect and improve the image quality.