1. An alignment method for a lithography apparatus, comprising: determining a plurality of data points associated with an object that moves with a wafer table, the data points including a position and radiation intensity associated with the position; and performing an interpolation of the plurality of data points to produce a best fit curve, wherein the performing the interpolation comprises adjusting a weighting assigned to the plurality of data points during the interpolation to provide less weight to the densely spaced data points and more weight to the sparsely spaced data points.