Metrological data is known to be blurred by the imperfections of the measuring process. For about two centuries, regular or constant errors were not the focal point of experimental activities, only irregular or random errors were. To address this here, Truth and Traceability in Physics and Metrology discusses a new error concept that dispenses with the common practice to randomize unknown systematic errors. Instead, unknown systematic errors are treated as what they are, namely unknown constants. Furthermore, the ideas considered point to a methodology to steadily localize the true values of the measures and, consequently, traceability.