MAPPING LAND-COVER OVER LARGE AREAS USING MULTISPECTRAL DATA DERIVED FROM THE NOAA-AVHRR - A CASE-STUDY OF NIGERIA

Land-cover information for Nigeria was obtained from a countrywide, lo w-level aerial survey conducted in 1990. A range of spectral vegetatio n indices (SVIs) and ground surface temperature estimates were calcula ted for Nigeria using daily data throughout 1990 from the National Oce anic and Atmospheric Administration's (NOAA) Advanced Very High Resolu tion Radiometer (AVHRR) data. A supervised classification of the land- cover classes was then performed using a modified discriminant analysi s in which predictor variables were selected from the mean, maximum, m inimum and standard deviation of the raw waveband AVHRR data, AVHRR de rived products and a digital elevation model (DEM). With a 60 per cent threshold coverage by any one of eight major vegetation types the ana lysis correctly predicted land-cover type with producer accuracies (ex cluding 'bare ground' with only a few points) of between 48 per cent ( cultivation) and 100 per cent (mangrove) (average = 74.5 per cent).