... We present the algorithm and implementation details for the robust, realtime bandpass removal and calibration routine developed for the HI Parkes All Sky Survey project. ... Traditionally, the bandpass that is present in single-dish 21 cm spectra is removed by observing in a ``signal-reference'' mode. ... The robust bandpass removal algorithm implemented for the HIPASS Project successfully produces calibrated HI emission line spectra for most of the survey data. ...