The most obvious difference between Bitoba and Delta is that the former has few measuring points, while the latter is multi-point measurement, so it is easy to realize grid layout measurement in the pipeline. The former can't be realized, and the correction explanation for this fatal shortcoming is: "After a lot of blowing, a rich database has been created" and "realized by correction calculation". Anyone who knows a little about industry should know that the straight section of air duct in industrial site is often relatively small, which can not meet the measurement requirements, and the wind field is complex. Baffle doors, supports and airflow distribution all make the wind field very complicated, especially in large-diameter air ducts, where the speed difference between points is extremely large, and even in many places it is reversed. Under such conditions, can it be solved by database modification? As far as I know, there is nothing special about Bito Bar. It can be said that it only optimizes the classic Bito Bar in several aspects.