Time transfer through GPS

Commonly available GPS receivers have, these days, hardware outputs of 1 pps. These receivers normally have the time accuracy within 100 ns. But if these are not calibrated in advance, they cannot be recommended for precise on-line applications. However, common view mode GPS time transfer using single satellite is in use for the generation of Coordinated Universal Time (UTC) by ensembling more than 40 clocks scattered all over the world. Use of carrier phase in common view mode is being explored. The initial results are quite encouraging. The paper reviews the current status of these time transfer techniques via GPS.