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The California Plate Boundary Observatory GPS-GNSS Network

Christian Walls, Doerte Mann, Ryan C. Turner, Andre Basset, Shawn Lawrence, Kenneth Austin, Stephen T. Dittman, Karl Feaux, & Glen S. Mattioli

Published August 15, 2016, SCEC Contribution #7019, 2016 SCEC Annual Meeting Poster #144

The EarthScope PBO GPS-GNSS network in California, funded by the NSF and operated by UNAVCO, is comprised of 599 permanent GPS and GNSS stations spanning three principal tectonic regimes and is administered by separate management regions (Subduction - Pacific Northwest [91 sites], Extension - East [41 sites], Transform - Southwest [467 sites]). Since the close of construction in September 2008 various enhancements have been implemented through additional funding by the NSF, NOAA, and NASA and in collaboration with stakeholders such as Caltrans, Scripps, and the USGS.

Initially, the majority of stations used first generation IP based cellular modems and radios capable of ~10KB/s data transfer rates. Aside from 1-2MB daily downloaded files the bandwidth limitation was a challenge for regional high-rate data downloads for GPS-seismology and airborne LiDAR surveys, and real-time data flow. Today, only 5 of the original cell modems remain with 338 upgraded cell modems providing 3G/4G/LTE data communications with transfer rates ranging from 80-400 KB/s. Ongoing radio network expansion and upgrades continue to harden communications using the 900MHz, 2.4GHz and 5.8Ghz spectrums. 27 VSAT and one manual download site remain (down from 60 VSAT & 12 Manual in 2008). In California, the network capabilities for 1Hz & 5Hz downloads or low latency 1 Hz streaming are ~95%, ~85% and ~70%, respectively. In general, nearly all custom data requests for high rate data are accommodated without delay from communications limitations.

During the past year, uptime ranged from 95-100% with data return for 15 s data exceeding 99%. 200 additional California sites were added in March 2016 to the real-time (1Hz) system and data from 410 sites are distributed in BINEX and RTCM 2.3/3.1 formats with an average latency of ~0.7 s and completion of ~85%. These include some challenging locations such as the Channel Islands and the Sierras. A variety of geophysical sensors are co-located with a subset of the stations and include: 21 MEMS accelerometers, 31 strong motion and broadband seismometers, 9 borehole strainmeters and 1 long baseline strainmeter. Vaisala meteorological instruments are located at 53 sites of which 52 stream GPS/Met data. As budget allows, GPS-only receivers are replaced with GNSS receivers and antennas. Today, 120 stations in California are GLONASS enabled NetR9 receivers or full constellation Septentrio PolaRx5 receivers.

Key Words
GPS GNSS Geodesy Real-Time

Walls, C., Mann, D., Turner, R. C., Basset, A., Lawrence, S., Austin, K., Dittman, S. T., Feaux, K., & Mattioli, G. S. (2016, 08). The California Plate Boundary Observatory GPS-GNSS Network . Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy