We present a methodology adopted to extract planetary wave information from a set of interferometric data. The data set represent information collected by a Bomem interferometer from 1993 until 1995 in Stockholm, Sweden. We also discuss several procedures other than that adopted for the analysis of this unevenly spaced data and provide the rationale for the adopted procedure. New results on planetary waves are presented. A robust analytical procedure for analyzing gappy data containing information within a known band is also presented. The procedure, consisting of a periodogram method followed by the application of a moving average filter with a correction function, would be used on future data.