A recent work project involved a number of unit conversions between various systems of measurements. Due to the scale and critical nature of the project, we wanted to ascertain that our conversion factors were as accurate as possible.
While only tangentially related, what I couldn't determine was who held final authority in declaring what the "one true" conversion factors should be.
For example, NIST provides a set of conversions and does not make explicit reference to other standards organizations. This article on International Bureau of Weights and Measures (BIPM) implies that the BIPM is responsible for declaring those conversion factors.
Is there a single organization responsible for declaring and verifying the accuracy and precision of conversions?