International time and frequency comparisons in real time: Recent results

Within the Sistema Interamericano de Metrologia (SIM) region, a time comparison network, SIMTN, has been developed. The SIMTN continuously compares the time scales of SIM members and publishes measurement results in near real-time. The measurements are made with Global Positioning System (GPS) common-view and all-in-view techniques, and data are exchanged and published via the Internet every 10 minutes. As of January 2012, the time scales of national metrology institutes (NMIs) located in 17 nations have joined the SIMTN. The resources of these local time scales are combined to generate the SIM Time Scale (SIMT), which publishes new data every hour via the Internet. These hourly updates show the current time difference between SIMT and the local time scales maintained by each SIM NMI, known as SIMT(k).