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The SIM Network:  Improved Time Coordination for North, Central, and South America



Jose M. Lopez, Michael A. Lombardi, Andrew Novick, Jean-Simon Boulanger, R. de Carvalho, R. Solis, Francisco Jimenez


The Sistema Interamericano de Metrologia (SIM) consists of national metrology institutes (NMIs) located in the 34 member nations of the Organization of American States (OAS), which extends throughout North, Central, and South America, and the Caribbean region. SIM is one of the world s five major regional metrology organizations (RMOs) recognized by the Bureau International des Poids et Mesures (BIPM). Currently about half of the 34 member NMIs maintain time and frequency laboratories.  In order for these NMIs to establish metrological traceability and to determine the uncertainty of their measurements, it is important for each of them to participate in international comparisons. The SIM network was developed to advance the state of metrology in the SIM region and to allow as many laboratories as possible to participate in international time coordination.  It provides continuous, near real-time comparisons between the national time and frequency standards located throughout the SIM region, by utilizing the technology of both the Internet and the Global Positioning System (GPS).  As of early 2008, ten SIM NMIs have are participating in the SIM network, and six additional NMIs are expected to be added to the network as soon as resources become available.  The paper provides an overview of SIM and a technical description of the network.  It also discusses the network s measurement uncertainties and presents results obtained from ongoing interlaboratory comparisons.
Proceedings Title
Proc. 2008 EFTF Conf.
Conference Dates
April 23-25, 2008
Conference Location
Toulouse, 1, FR
Conference Title
2008 European Frequency and Time Forum


common-view, GPS, metrology, time transfer, traceability


Lopez, J. , Lombardi, M. , Novick, A. , Boulanger, J. , de Carvalho, R. , Solis, R. and Jimenez, F. (2008), The SIM Network:  Improved Time Coordination for North, Central, and South America, Proc. 2008 EFTF Conf., Toulouse, 1, FR, [online], (Accessed June 24, 2024)


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Created April 22, 2008, Updated October 12, 2021