The successful launch of the GOES-N spacecraft will provide the first series of GOES solar EUV irradiance measurements. The new measurements will provide users with detailed observations of the absolute value of solar EUV energy flux and the temporal variance on time scales as short as seconds. Each EUV sensor (EUVS) in the GOES-N series is a transmission grating based instrument, similar to the SOHO/SEM instrument. We have studied the design of the GOES-N EUVS from the EUVS Calibration and Data Handbook with a focus on the Field Of View (FOV) sensitivity to alignment and solar pointing. In this work, we have developed a new algorithm that includes changes in the instrument calibration as a function of solar pointing as well as the spatial distribution of solar intensity across the disk. The new calibration algorithm has been used to develop a new time series of GOES EUVS data collected during the GOES-N Post-Launch Test period (PLT) and these results are reported in the companion paper.