Abstract
The availability of ZY-3 satellite data provides additional potential for surveying, mapping, and quantitative studies. Topographic correction, which eliminates the terrain effect caused by the topographic relief, is one of the fundamental steps in data preprocessing for quantitative analysis of vegetation. In this paper, we rectified ZY-3 satellite data using five commonly used topographic correction models and investigate their impact on the regression estimation of shrub forest leaf biomass obtained from sample plots in the study area. All the corrections were assessed by means of: (1) visual inspection (2) reduction of the standard deviation (SD) at different terrain slopes (3) correlation analysis of different correction results. Best results were obtained from the Minnaert+SCS correction, based on the non-Lambertian reflection assumption. Additional analysis showed that the coefficient correlation of the biomass fitting result was improved after the Minnaert+SCS correction, as well as the fitting precision. The R2 has increased by 0.113 to reach 0.869, while the SD (standard deviation) of the biomass dropped by 21.2%. Therefore, based on the facts, we conclude that in the region with large topographic relief, the topographical correction is essential to the estimation of the biomass.
Highlights
Shrub biomass is one of the best indicators of shrub productivity and an important input for the study of ecological systems; at the same time, biomass is an important basis of the material cycle and the energy conversion
We drew the following conclusions: (1)The topographic correction model based on Lambertian reflection theory tends to cause excessive correction due to the sky diffuse reflection and the surrounding terrain
The models based on non-Lambertian reflection assumption yield better correction results
Summary
Shrub biomass is one of the best indicators of shrub productivity and an important input for the study of ecological systems; at the same time, biomass is an important basis of the material cycle and the energy conversion. Shrubs grow mostly in arid areas as well as in semi-arid mountains, where the illumination often results in the canopy surface oriented towards the sun receiving more solar radiation than that oriented away from the sun on the opposite slope This radiation difference caused by the topographic relief in the remote sensing image, apart from the anisotropic reflection properties of the ground (Bidirectional Reflectance Distribution Function, BRDF effects), is called the topographic effect. As a result, it has been recognized as an important factor responsible for the same object having different spectral response in images obtained from mountainous area [5], which seriously affects the quantitative inversion of vegetation parameters, as well as surface parameters
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