Selecting Representative High Resolution Sample Images for Land Cover Studies. Part 1: Methodology

This is the first of two articles which explore the comtained using the TM map. The performance of samples selected by a combination of cover composition and conbined use of coarse and fine resolution data in land cover studies. It describes the development and evaluation of tagion index responded to the characteristics of individual tiles in terms of the selection criteria. A rigorous applian objective procedure to select a representative sample of tiles of high resolution images that complements a cation of the algorithm with spatial heterogeneity measures such as the contagion index is computationally very decoarse resolution coverage of an entire region of interest. The second article explores the use of the procedure for manding. It is concluded that PSA provides an efficient and effective tool to select a representative sample for land an accurate estimation of cover type composition at the regional scale. The Purposive Selection Algorithm (PSA) cover studies in which both large area coverage and local detail are desired. Elsevier Science Inc., 2000 assumes that a relationship exists between land cover compositions at the two spatial scales. It selects one tile at a time, seeking the sample which most closely resembles the composition of the coarse resolution map. Two INTRODUCTION selection criteria were used, fraction of cover types and The interest in land cover analysis at regional to global contagion index. PSA was evaluated using two land cover scales has grown dramatically in the last decade, stimumaps for a 288 km3165 km area in central Saskatchelated by global environmental change and by improved wan, Canada derived from Landsat Thematic Mapper mapping tools. The International Geosphere–Biosphere images (30 m pixels) and Advanced Very High Resolution Program (IGBP) identified a strong need for regional Radiometer (AVHRR, 1000 m pixels), each divided into and global land cover information (Townshend et al., 64 tiles. The performance of an intermediate sensor (48