Simulation analysis on the relationship between the leaf area index and polarimetric parameters of crops

The leaf area index(LAI)is an important parameter to quantitatively describe the structure of vegetation and crops.Uncertainty in the relationship between the LAI and polarimetric parameters is the key problem for LAI estimation from polarimetric synthetic aperture radar(POLSAR)data.However,the existing POLSAR data have difficulties meeting the demand of the aforementioned research.This paper analyses the correlations between the LAI and the polarimetric parameters derived from Cloude and Freeman decompositions using simulated POLSAR data based on a coherent scattering model for maize and wheat.The results show:(1)The POLSAR data at C-band with a large incidence angle(40 degrees)are very suitable for finding the LAI for maize and wheat.(2)For maize there is a strong correlation between the scattering type angle and the LAI at C-band with a large incidence angle,and the coherency entropy,anisotropy,and the power of the double-bounce scattering power component also have significant correlations with the LAI.(3)For wheat at Cband with a high incidence angle,although the correlation coefficient is low,there is still a correlation between the entropy,anisotropy and LAI.Besides,the volume scattering is suitable for extracting the LAI for wheat at X-band.

Terrain topographic inversion using single-pass polarimetric SAR image data

The shift of polarization orientation angle y at the maximum of co-polarized or cross-polarized back-scattering signature can be used to estimate the surface slopes. It has been utilized to generate the digital elevation mapping (DEM) and terrain topography using two-pass fully polarimetric SAR or interferometric SAR (INSAR) image data. This paper presents an approach to DEM inversion by using a single pass of polarimetric SAR data. The y shift is derived, by using the Mueller matrix solution, as a function of three Stokes parameters, Ivs, Ihs, Us, which are measured by the SAR polarimetry. Using the Euler angles transformation, the orientation angle y is related to both the range and azimuth angles of the tilted surface and radar viewing geometry, as has been discussed by many authors. When only a single-pass SAR data is available, the adaptive thresholding method and image morphological thinning algorithm for linear textures are proposed to first determine the azimuth angle. Then, making use of full multi-grid algorithm, both the range and azimuth angles are utilized to solve the Poisson equation of DEM to produce the terrain topography.

The consistency between Na content distribution at the subsurface and the lake body’s movement in Lop Nur

Historically,Lop Nur was a large and famous salt lake that acted as an important geographic position along the ancient‘Silk Road’,and was associated with the surrounding old civilizations,such as Loulan and Haitou.However,it dried up before 1972.It shows a clear‘Ear’feature on synthetic aperture radar(SAR)images.The objective of this paper is to interpret Lop Nur’s environmental evolution during its drying-up process based on an analysis of its sodium sedimentary feature.The genetic algorithm-partial least squares approach is introduced as a modeling method to retrieve the subsurface sodium content from polarimetric parameters obtained by Cloude decomposition.As a result,the R2 and root-mean-square error can reach 0.7 and 9.1 g/kg.It is suggested that the subsurface salt content was the primary reason for the bright-grey strips textures on SAR images.Furthermore,our results show that the sodium content along the same strip changed,with its distribution exhibiting consistency with the lake body’s movement driven by the strong wind.In future,high-precision topographical data will be considered,and should be helpful in the analysis of lake body movement.The method of this paper can also be applied in other similar dried salt lakes.