Research Online: GPS UTC anomaly, spatial reference system access

April 26, 2017  - By
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Impact of January 2016 GPS UTC Anomaly

By Charles Curry / Presented at ION ITM, January 2017

On Jan. 26, 2016 alarms occurred on GPS timing receivers around the globe. This article tells the story as experienced by the Chronos support team over a four-day period, dealing with nearly 5,000 alarm events from many different GPS timing receivers worldwide. It examines whether the alarms were service-affecting or if the equipment switched to a resilient fallback status. This event was not without precedent. The last time such an event happened to the GPS transmission was Jan. 1, 2004, and coincidentally SVN23 was also to blame then. A major network event happened to GLONASS on April 1, 2014. These qualify as “Black Swan Events” first proposed by Nassim Nicholas Taleb in his 2001 book, Fooled by Randomness. This was a unique event with unique impact across the globe. Chronos supports many thousands of GPS-based timing receivers for more than 100 clients in more than 50 countries. This article also reviews more recent work to understand what caused the event and how it manifested itself.

National Spatial Reference System Access in 2022

By Daniel Roman, NOAA / Presented at ION ITM, Jan 2017

In 2022, the National Geodetic Survey will implement a new datum to replace both the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88). This datum will provide the primary access to the National Spatial Reference System (NSRS) through GNSS and a geopotential model. Foundation CORS sites will provide a backbone network to ensure that the U.S. contributions to the ITRF solutions remain robust. In turn, these sites will also provide the connection to the densified network of CORS stations to provide local access. RTN and RTK surveys will provide an additional layer of access for improved local resolution. Velocities will be taken into account to provide tie back to survey points. Passive control (benchmarks) will become secondary access to the NSRS with conversion models being provided to ensure backward compatibility to NAD 83 and NAVD 88.

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