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 multitemporal local area coverage imagery obtained by the Advanced Very-High Resolution Radiometer on NOAA-9 and NOAA-11 orbiting platforms, clearly 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 difference vegetation index, for two successive time periods, such as hydrological years. In establishing the time-trajectory, the indicator is composited for each pixel in a registered multidate image sequence. The change vector is simply the vector difference between successive time-trajectories, each represented as a vector in a multidimensional measurement space. The length of the change vector indicates the magnitude of the interannual change, while its direction indicates the nature of the change. A principal components analysis of change vectors for a Sudanian-Sahelian region in West Africa shows four major classes of change magnitude and four general contrasting types of change. Scene-specific changes, such as reservoir water level storage changes, are also identified. The technique is easily extended to other biophysical parameters, such as surface temperature, and can incorporate noneuclidean distance measures. Change vector analysis is being developed for application to the land-cover change product to be produced using NASA's Moderate-Resolution Imaging Spectroradiometer instrument, scheduled for flight in 1998 and 2000 on EOS-AM and -PM platforms.