Specifies the maximum difference between the ratios derived from observed features, and those in the database with which a match is attempted.
The difference is evaluated by calculating
ABS( 1 - ABS( observed / reference ) )
giving a fractional measure of the difference. For example: difference = 0.01 indicates that the two quantities differ by approximately 1% of their average magnitude. Values much larger than 0.1 are likely to generate a lot of coincidence matches, values less than 0.01 may well miss 'good' matches in less-than-ideal data.
The default value is 0.03.
Martin Clayton