GNSS disciplined references use timing information from the GNSS to synchronize a local reference. Long-term accuracy on the order of E-12 is common. The GNSS oscillator can be crystal or atomic with a wide range of performance options depending upon the specific requirement. A range of configurations are available from PCB assembles that can be easily embedded into a system, to rack mount units with up to sixteen channels. Self-calibrating references essentally eliminate long-term drift by storing the current calibration coefficients for the 10 MHz OCXO in FLASH memory (see demonstartion video). Kits are available complete with the selected GNSS locked source, antenna, power supply and cable - everything you need to have a fully operational source. GNSS locked oscillator products are considered to be frequency standards by NIST (NIST white paper). Most GNSS locked references also provide the PPS ( pulse per second) and NMEA 0183. The algorithms for locking the ocxo to the GNSS offer a wide range of sophistication. Some configurations can be as simple as a PLL while others use complex algorithms to provide improved phase noise. In additio to algorithms to lock the OCXO,  there are also complex algorithms used to stabilize the PPS. PPS jitter is in large part due to transmission effects which can add 5 to 10 ns of pulse to pulse jitter. Processing can improve jitter to below 1 ns.