1. A method for quantifying and removing offset bias signals in a chemical array data set having one or more channels, said method comprising: for each channel of data in the chemical array data set, and using at least one computer processor, selecting a first set of features from the data set; calculating surface intensities for each feature in the first selected set of features; calculating a spread of the intensity values of the first selected set of features from the calculated surface intensities; selecting a second set of features the intensity values of which are within a range of intensity values between ± spread times a predetermined multiplier; calculating surface intensities for features in the second selected set of features; calculating surface intensities for all other features in the data set for the channel from the calculated surface intensities for each feature in the second selected set; correcting feature intensities of the channel features by subtracting the surface intensities for each feature in the second selected set at locations that correspond to respective locations of said feature intensities; and outputting the corrected feature intensities.