The quality of powder bed fusion (PBF) built parts is highly correlated to the melt pool characteristics. Camera-based coaxial melt pool monitoring (MPM) is widely applied today because it provides high-resolution monitoring on the time and length scales necessary for deep PBF process understanding, in-process defect detection, and real-time control. For such functions, MPM data has to be registered correctly to a well-defined coordinate system. This paper presents methods for camera-based coaxial melt pool monitoring (MPM) data registration using the build volume coordinate system defined in ISO/ASTM52921, for both open architecture AM systems and 3rd party MPM augmented closed commercial systems. Uncertainties are evaluated for the proposed methods and case studies provided to demonstrate the effectiveness of the methods.