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 data set, 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 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 surface intensities at locations that correspond to respective locations of said feature intensities; and outputting the corrected feature intensities.