Location: Hydrology and Remote Sensing Laboratory
Title: Global characterization and monitoring of forest cover using Landsat data: opportunities and challanges Authors
Submitted to: International Journal of Digital Earth
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2012
Publication Date: August 24, 2012
Citation: Townshend, J., Masek, J., Huang, C., Vermonte, E., Gao, F.N., Channan, C., Sexton, J., Fenng, M., Narasimhan, R., Kim, D., Song, K., Song, D., Song, X. 2012. Global characterization and monitoring of forest cover using Landsat data: opportunities and challanges. International Journal of Digital Earth. DOI: 10.1080/17538947.2012.713190. Interpretive Summary: Landsat imagery provides spatial details for land cover and land cover change studies. However, the global products of forest cover and cover changes at a Landsat scale have not become possible until recently, thanks to the freely available Landsat data and the low costs of computing. This paper describes the methodology to create global products at a Landsat resolution. The challenges caused by the differences in atmosphere, terrain and phenology conditions in Landsat data were discussed. Approaches to reduce these effects have been developed and tested. A global prototype product for forest cover and forest cover change was included. This work demonstrates an automated framework for producing global land cover and land cover change products from Landsat data. The forest cover and cover change maps at the Landsat scale are critical for the understanding of carbon and water cycles for regional and global climate models. The forest and change map also provides additional data sources for the USDA Forest Service.
Technical Abstract: The compilation of global Landsat data-sets and the ever-lowering costs of computing now make it feasible to monitor the Earth’s land cover at Landsat resolutions of 30 m. In this article, we describe the methods to create global products of forest cover and cover change at Landsat resolutions. Nevertheless, there are many challenges in ensuring the creation of high-quality products. And we propose various ways in which the challenges can be overcome. Among the challenges are the need for atmospheric correction, incorrect calibration coefficients in some of the data-sets, the different phenologies between compilations, the need for terrain correction, the lack of consistent reference data for training and accuracy assessment, and the need for highly automated characterization and change detection. We propose and evaluate the creation and use of surface reflectance products, improved selection of scenes to reduce phonological differences, terrain illumination correction, automated training selection, and the use of information extraction procedures robust to errors in training data along with several other issues. At several stages we use Moderate Resolution Spectroradiometer data and products to assist our analysis. A global working prototype product of forest cover and forest cover change is included.