Development of a 1-km landcover dataset of China using AVHRR data

This paper describes the development of a 1-km landcover dataset of China by using monthly NDVI data spanning April 1992 through March 1993. The method used combined unsupervised and supervised classification of NDVI data from Ž . AVHRR. It is composed of five steps: a unsupervised clustering of monthly AVHRR NDVI maximum value composites is Ž . performed using the ISOCLASS algorithm; b preliminary identification is carried out with the addition of digital elevation models, eco-region data and a collection of other landcoverrvegetation reference data to identify the clusters with single Ž . landcover classes; c re-clustering is performed of clusters with size greater than a given threshold value and containing two Ž . or more disparate landcover classes; d cluster combining is performed to combine all clusters with a single landcover class Ž . in one cluster, and all other clusters into one mixed cluster; and e supervised classification is used to carry out post-classification of the mixed cluster generated in the previous step by using the maximum likelihood algorithm and the identified single landcover classes of the previous step as training data. The classification is based on extensive use of computer-assisted image processing and tools, as well as the skills of the human interpreter to take the final decisions regarding the relationship between spectral classes defined using unsupervised methods and landscape characteristics that are used to define landcover classes. q 1999 Elsevier Science B.V. All rights reserved. Ž .