Establishing the Downscaling Model of NDVI Based on the Iterated Function System

The moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) product plays an important role in eco-environmental monitoring of natural disasters. However, its validation has long been an important scientific problem that has yet to be resolved. In this study, the downscaling model of NDVI was established based on the fractal Iterated Function System (IFS), and the MOD13 Q1 product was then validated based on the model. Xiamen was selected as the core study area, and utilizing the 30 m resolution Landsat 8 operational land imager (OLI) images as the validation data, the validation of MOD13 Q1 was implemented. The results showed the following. (1) The overall quality of the MOD13 Q1 product is good. While in the NDVI range of 0.2 to 0.6, the MOD13Q1 has an overestimation and the difference recognition of the NDVI is low, which should be paid attention to in practical applications; (2) The experiment proved that the fractal IFS was an effective methodology to establish downscaling models for RS land surface parameters such as NDVI. The inherent physical meaning and dynamic process expression advantages of this method make it have great application potential, which needs further digging.