In this paper we have developed some improvements on the commonly used methodologies in order to obtain accurate maps of sea surface temperature (SST). These improvements permit us: (1) to calibrate without bias AVHRR channels including non-linear corrections; (2) to get geometrically corrected maps for the complete scan width of AVHRR (3000 km) with a subpixel accuracy; (3) to detect clouds over the sea; and (4) to make atmospheric and emissivity correction for all zenith angles from nadir to the outermost off-nadir view of AVHRR images (68.9 ) and for different types of atmospheres. The theoretical base of the improvements used is detailed in each section, and an example is also included in each section in order to better explain how they are applied in a practical situation. The methodologies developed here can be profitable for any user interested in accurate retrievals of SST such as meteorologists, climatologists and oceanographers.