A ranging code correlation function detection system for use in a global navigation satellite system (GNSS) receiver includes a correlation block to correlate a digitized GNSS signal (e.g. at or above a critical sampling rate) with a corresponding ranging code at each of a plurality of different offsets from a current estimate of a code delay to generate a plurality of correlation data points; an interpolation filter configured to generate at least one estimated correlation data point that lies between two of the correlation data points based on the current estimate of the code delay. In some cases the ranging code correlation function detection system may also include a discriminator block configured to generate an updated estimate of the code delay based on the at least one estimated correlation data point.