Towards Jointly Validation of Land Remote Sensing Products In China

Abstract:

To assess the accuracy of remote sensing product (RSP) requires well designed and carefully implemented validation effort. However, validation is not a straightforward task. On the contrary, it is generally recognized as a challenging issue due to the inconsistence of resolutions and extents associated with various products, strong spatial and temporal variations of surface parameters and, the essential heterogeneity of land surfaces. Thus, to develop, design and conduct reasonable validation schemes and activities to acquire ground truth at pixel scale over heterogeneous land surfaces is urgently needed. This contains, from the perspective of measurement, to integrate various ground observations collected at multi-scale, in order to validating different RSPs from site to network, especially for those land surface variables with strong spatial-temporal variations. To this end, a dedicated validation initiative has been launched in China since 2011. The main scientific objectives and research contents of this project are to develop mathematical approaches for in situ sampling design to acquire ground truth at pixel scale over heterogeneous land surfaces, to form a series of recognized and practicable technical specifications to guide users to validate various RSPs, and to establish a prototype of national validation network and a RSP evaluation system. Specific validation activities, such as the HiWATER, were conducted from site to network, through multi-scale observations collected from multi-platform and multi-source, to experimentally examine those proposed methodologies and guidelines. Corresponding research outcomes on the development of sampling design, scale method and validation of land surface variables have already yielded. This enables validation efforts to be more effective for heterogeneous land surfaces and applicable for other validation tasks beyond local and regional scale. Following the experience of these validation exercises, we are coordinating a Chinese validation network to use standardized and recognized technical specifications in implementing future validation attempts, aiming to extend validation exercises from point scale to regional scale and to national scale across different zones.