utilize compensations for cumulative error cea reversal error rea and zero positioning error zpa the adjusted error value ae r i of an associated error value e r i where the value of r is even is calculated as follows whereas the adjusted error value ae r i of an associated error value e r i where the value of r is odd is calculated as follows when adjusted error values are employed the resulting value of u0113 rev is useful in determining the effect that the various compensations i e cumulative error reversal error and zero positioning error have on reversal error the methodology next progresses to block 150 where at least a portion of the values of e r i are employed to mathematically develop the line ec shown in fig4 since values of e r i where the value of r is even are known to include reversal error which is calculated above steps must be taken to factor this error out so as not to improperly affect the calculation of cumulative error one method by which reversal error may be isolated from the calculation of cumulative error is to use only those values of e r i where the value of r is odd the slope m of the line e c is then provided by the equation m 2 u00d7 u2211 i 0 n u2062 e 1 i e 3 i u2026 e r 1 i r 2 l u00d7 n 4.