Validation methods of LAI products based on scaling effect

Validation is one of the most important processes to assess the products of remotely sensed data and to evaluate whether the products accurately reflect the land surface configuration. Leaf Area Index (LAI) is a key parameter which represents the vegetation canopy structure and growth conditions. Accurate evaluation of coarse resolution LAI products is the basis to apply them to the land surface models. In this study, validation methods of coarse resolution LAI products for heterogeneous pixels are established based on the scaling effect and the scaling transformation. Taking spatial heterogeneity and growth difference into account, we transform LAI from field measurements to 1 km resolution scale with the help of higher resolution images, and validate it using MODIS (Moderate Resolution Imaging Spectrometer) and GLASS (Global Leaf Area Index Products) LAI products. Two study areas in Hebi City, Henan Province, China and Yingke Oaisis, Zhangye City, Gansu Province, China were selected for the validation of LAI products. Results show that both MODIS and GLASS LAI products underestimate the true LAI. Compared with MODIS products, GLASS products better reflect the true situation.