PROCESSING ERROR REDUCTION FACTORS IN THE GENERATION OF GEOMETRICALLY CORRECTED NOAA AVHRR VEGETATION INDEX IMAGES

The study of multitemporal data needs geometric registration of each image with a standard master image. The role is described of a narrower distribution of ground control points in the across-track direction with respect to the area of interest in minimizing the registration error. The 1.1 km spatial resolution of the Advanced Very High Resolution Radiometer (AVHRR) on-board the National Oceanic and Atmospheric Administration (NOAA) meteorological satellites has contributions from varying degree of vegetation characteristics within the pixel dimensions. The contrast among the vegetated, less intensely vegetated and non-vegetated pixels are enhanced in the Normalized Difference Vegetation Index (NDVI) image due to the use of a very high gain factor in converting the observed range of NDVI values to 8-bit scale. Also discussed is the radiometric misrepresentation in the grey values of new pixels created by geometrical correction applied directly to a vegetation index image.