The four constellations (GPS, Glonass, Galileo, BeiDou) we use for sub-meter GNSS mapping have come a long way since WAAS/SBAS was introduced. Here's what you need to know about using these constellations for high-accuracy data collection today from the Eos March 2017 issue.
On December 31st, 2016, just before midnight, a positive leap second was inserted into the Coordinated Universal Time (UTC). This leap second added to GLONASS may have introduced disruption at the exact moment. Arrow Series™ receivers affected (e.g., Arrow 200, Arrow Gold) will automatically update a new almanac.