It is mentioned here the design philosophy and basic experiments how the radar data should be processed for the digital tracking computation. Aircraft data of search radar, obtained scan by scan, are recorded on perforated tapes through the radar video digitizer (RVD) and the buffer memory devices. The track-while-scan technique is investigated by an off-line computer using these recorded data. Here are given some proposals concerning-----data rejection and acceptance. It is also clarified the relation between the accuracy of RVD and tracking calculations.