Truth and traceability in physics and metrology Metrological data is known to be blurred by the imperfections of the measuring process. In retrospect for about two centuries regular or constant errors were no focal point of experimental activities only irregular or random error were. Todays notation of unknown systematic errors is in line with this. Confusingly enough the worldwide practised approach to belatedly admit those unknown systematic errors amount to considering them as being random too. This book discusses a new error concept dispensing with the common practice to randomize unknown systematic errors. Instead unknown systematic errors will be treated as what they physically are namely as constants being unknown with respect to magnitude and sign. The ideas considered in this book issue a proceeding steadily localizing the true values of the measurands and consequently traceability.