HydroUnits: supporting dimensional analysis in hydrologic computing systems using sensor-based standards

Abstract

Unit representation in the Transducer Electronic Data Sheet (TEDS) specified in the IEEE 1451 standards is a binary sequence of 10 octets that encode the physical units as a product of the seven Système International base units, plus radian and steradian, each raised to a rational power in addition to an unsigned integer indicating the structure of the unit. While this representation seems trivial, manual compilation is prone to be erroneous and impractical, especially for complex units used in the hydroclimatology field. Hence, the development of a software application to automatically generate this vector represents a critical step to both reduce work load and automate unit conversion. Existing conversion packages for manipulating units fall short in many ways and also suffer from not integrating with a units controlled vocabulary. We developed HydroUnits (Python-based) to compute the vectorial representation for the Consortium of Universities for the Advancement of Hydrologic Sciences, Inc's Observations Data Model units for use in an IEEE 1451.0-based TEDS generator. In addition, the package has been extended to support dimensional analysis, unit reduction and unit conversion and contains provision to convert time series data between different unit systems.