US Total Electron Content (Vertical and Slant)
The US Total Electron Content (US-TEC) product, which evolved through a collaboration between
the Space Weather Prediction Center *
(SWPC), the National Geodetic
Survey (NGS), the National Geophysical Data Center
(NGDC), and the Global Systems Division (GSD), is designed
to specify Vertical and Slant TEC over the Continental US (CONUS) in near real-time.
The product uses a Kalman Filter data assimilation model, described in the SWPC
This technique is driven by data from ground-based Global Positioning System (GPS)
dual frequency receivers. The primary data stream comes from the Maritime and
Nationwide Differential GPS (M/NDGPS) real time network of stations operated by
the US Coast Guard (USCG), and is provided to SWPC by the NGS continuously operating
Secondary data streams are provided by the
(meteorological application of GPS data) and the Real Time
IGS (International GNSS Service)
network. Currently, there are about 80 CORS, 30 GPS/Met, and 15 IGS stations ingested
into the model. This number has been gradually increasing and will be augmented by
Federal Aviation Administration/Wide Area Augmentation System (FAA/WAAS) data in the future.
The Real-Time US-TEC Product
is provided by SWPC as part of its mandate to provide real-time monitoring and forecasting of
solar and geophysical events. NGDC is the National Archive for the US-TEC product output and
the CORS data.
The US-TEC product includes maps over the Continental US (CONUS) of
- the vertical total electron content (TEC)
- an estimate of the uncertainty in the map
- the recent trend based on the departure of the TEC from the previous 10-day average
- ACSII Data files of the vertical and slant path TEC
The slant path data files specify the line-of-sight electron content to the GPS satellites
in view at the time. This ionospheric product is designed for estimating the signal delay
for single and dual frequency GPS applications. Note that TEC values in regions outside of
the CONUS have no data and should be treated with caution.
- USTEC Product Format (Readme)
- Products for 2013 and 2014 are available online
- Products for earlier years can be requested from Rob Redmon (firstname.lastname@example.org)
The full list of available day files can be viewed here.
- Access to historic US-TEC notable events prior to the established archive.
US Total Electron Content Real-time Specification is now fully operational as of June 19, 2007.
For more information on US-TEC or to comment on the US-TEC product, please visit the
real-time US-TEC Web.
*The Space Weather Prediction Center (SWPC) was formerly known as the Space Environment Center (SEC).