Validation of scale effect based on computer simulation model

With the developing of satellite technology, more and more sensors, based on various resolutions and functions, are launched to the sky to perform their missions. Enormous data are sent back to the Earth stations. In deriving surface parameters using these remotely sensed data, the transportability of algorithms from one resolution to another often cause the scale effect because of the surface heterogeneity on the Earth which can induce the change of reflectance. The problem, that the change of reflectance data affected by discontinuity as part of surface heterogeneity impacts the retrieval of vegetation leaf area index (LAI), is addressed in This work. Two cases, inducing the scaling issue in deriving surface parameters of interest, are considered here. One is the discontinuity between contrasting cover types within a mixed scene, the other is the nonlinear relationship of NDVI and LAI. Therefore, it is necessary to apply the correction based on NDVI-LAI relationships to modify scaling problem. In the processing, considering the field of wheat, firstly a series of 3D scenes with wheat and soil mixed are made based on the field measurement; secondly, computer simulation model $the method of radiosity, which can calculate the balance of light energy in the simulated scenes, is used to model BRF (bi-directional reflectance factor) of these scenes. If the NDVI-LAI relationship from homogeneous scenes can be taken as standard, the relationship from heterogeneous scenes will be modified according to contextural parameter. Some conclusions are drawn from the investigation: (1) different distributional contextures of vegetation even with the same LAI affect the reflectance heavily; (2) we compare the reflectance simulated by the method of radiosity with the mean reflectance calculated using the area-weighted linear relationship of reflectance from components, and find that the accuracy of the mean reflectance can be accepted so that the linear equation to calculate the reflectance of mixed pixels is reasonable to relate images with high and low resolution; (3) using contextural parameter for quantifying the scale effect can get promising results.