Abstract
NDVI values of GVI data derived from NOAA AVHRR data are fluctuated by various factors without land cover change. In order to utilize GVI data for global land cover monitoring, it should be considered these fluctuation factors. In this paper, these factors and their mutual relationship are discussed. Radiometric effect caused by solar zenith angle, change of solar zenith angle caused by the delay of satellite equator crossing time, sampling method of GVI data and inclination of scan angle mainly discussed. By this study, problems of GVI data were clarified.
