CHANGE-VECTOR ANALYSIS IN MULTITEMPORAL SPACE - A TOOL TO DETECT AND CATEGORIZE LAND-COVER CHANGE PROCESSES USING HIGH TEMPORAL-RESOLUTION SATELLITE DATA

Analysis of change vectors in the multitemporal space, applied to mult itemporal local area coverage imagery obtained by the Advanced Very-Hi gh Resolution Radiometer on NOAA-9 and NOAA-11 orbiting platforms, cle arly reveals the nature and magnitude of land-cover change in a region of West Africa. The change vector compares the difference in the time -trajectory of a biophysical indicator, such as the normalized differe nce vegetation index, for two successive time periods, such as hydrolo gical years. In establishing the time-trajectory, the indicator is com posited for each pixel in a registered multidate image sequence. The c hange vector is simply the vector difference between successive time-t rajectories, each represented as a vector in a multidimensional measur ement space. The length of the change vector indicates the magnitude o f the interannual change, while its direction indicates the nature of the change. A principal components analysis of change vectors for a Su danian-Sahelian region in West Africa shows four major classes of chan ge magnitude and four general contrasting types of change. Scene-speci fic changes, such as reservoir water level storage changes, are also i dentified. The technique is easily extended to other biophysical param eters, such as surface temperature, and can incorporate noneuclidean d istance measures. Change vector analysis is being developed for applic ation to the land-cover change product to be produced using NASA's Mod erate-Resolution Imaging Spectroradiometer instrument, scheduled for f light in 1998 and 2000 on EOS-AM and -PM platforms.