multiple measurements application of the interferogram partitioning principle ipp enables a cis system to exclude noisy sections of an interferogram from analysis that would be inextricable from spectral analysis the excellent sensitivity of cis can also be used to characterize the performance and stability of measurement instruments as used herein and in the appended claims the term u201c target region u201d is defined to include any location area or region of measurement within the optical path of the interferometer which contributes to the light received and consequently the interferogram generated as used herein and in the appended claims the term u201c composite interferogram u201d is defined to include any interferogram that contains information describing derived from or representing at least two interferograms each component interferogram contributing to a composite interferogram need not contribute an equal amount or type of information additionally a composite interferogram may contain only a portion of the information contained in its component interferograms furthermore the initial information contributed to form a composite interferogram need not be separable from the composite interferogram composite interferograms may be created by processes including but not limited to summation integration piecewise construction ratio of interferograms and additional physical and mathematical operations as used herein and in the appended claims the term u201c scaling u201d is defined to include the alteration of one or more characteristics of a data set for a two dimensional interferogram for example scaling may include but is not limited to expansion or compression along the horizontal axis vertical axis both axes or a portion or either or both axes scaling may include normalizing a data set so that the maximum or minimum intensity is the same across the multiple measurements scaling may also adjust one or more interferograms to achieve.