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TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.


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Journal Article
TL;DR: In this article, a least squares fitting procedure is used to remove instrumental biases inherent in the GPS satellite and receiver to construct two-dimensional maps of absolute TEC over Japan by using GPS data from more than 1000 GPS receivers.
Abstract: The dual frequency radio signals of the Global Positioning System (GPS) allow measurements of the total number of electrons, called total electron content (TEC), along a ray path from GPS satellite to receiver. We have developed a new technique to construct two-dimensional maps of absolute TEC over Japan by using GPS data from more than 1000 GPS receivers. A least squares fitting procedure is used to remove instrumental biases inherent in the GPS satellite and receiver. Two-dimensional maps of absolute vertical TEC are derived with time resolution of 30 seconds and spatial resolution of 0.15° × 0.15° in latitude and longitude. Our method is validated in two ways. First, TECs along ray paths from the GPS satellites are simulated using a model for electron contents based on the IRI-95 model. It is found that TEC from our method is underestimated by less than 3 TECU. Then, estimated vertical GPS TEC is compared with ionospheric TEC that is calculated from simultaneous electron density profile obtained with the MU radar. Diurnal and day-to-day variation of the GPS TEC follows the TEC behavior derived from MU radar observation but the GPS TEC is 2 TECU larger than the MU radar TEC on average. This difference can be attributed to the plasmaspheric electron content along the GPS ray path. This method is also applied to GPS data during a magnetic storm of September 25, 1998. An intense TEC enhancement, probably caused by a northward expansion of the equatorial anomaly, was observed in the southern part of Japan in the evening during the main phase of the storm.

194 citations

Journal ArticleDOI
TL;DR: In this article, a new technique for calculating the vertical total electron content (TEC) from ground-based ionosonde measurements is introduced, where the ionogram provides the information to directly calculate the vertical electron density profile up to the peak of the F2 layer.
Abstract: A new technique for calculating the vertical total electron content (TEC) from ground-based ionosonde measurements is introduced. The ionogram provides the information to directly calculate the vertical electron density profile up to the peak of the F2 layer. The profile above the peak is approximated by an α-Chapman function with a scale height that is derived from the profile shape around the F2 peak. The ionosonde TEC, or ITEC, is then calculated as the integral from 0 to ∞ over the entire profile. ITEC values from Digisonde observations at Millstone Hill, Wallops Island, and Jicamarca are compared with incoherent scatter radar and with Faraday and TOPEX satellite TEC measurements, showing very good agreement at middle latitudes and the magnetic equator.

193 citations

Journal ArticleDOI
TL;DR: An online, single station receiver bias estimation algorithm, IONOLAB-BIAS, is developed and implemented to obtain daily and monthly averages of receiver bias, and is observed that it is in excellent accordance with the sparse estimates from the IGS centers for all ionospheric states and regions.
Abstract: [1] Dual-frequency Global Positioning System (GPS) receivers present a plausible and cost-effective way of computing Total Electron Content (TEC) For accurate estimates of TEC, frequency-dependent satellite and receiver instrumental biases should be removed from GPS measurements properly Although instrumental satellite bias values are widely available through the internet from various International GPS Service (IGS) analysis centers, receiver biases (also known as differential code biases or interfrequency biases) are provided only for a very few GPS stations and a select number of days This makes it very difficult to compute TEC for a single station In this study, an online, single station receiver bias estimation algorithm, IONOLAB-BIAS, is developed and implemented to obtain daily and monthly averages of receiver bias The algorithm is successfully applied to both quiet and disturbed days of the ionosphere for stations positioned in high-latitude, midlatitude, and equatorial regions The receiver bias estimates are compared with two of the basic methods in the literature that can be applied off-line, and also with the receiver bias values provided from the IGS centers for a select number of stations It is observed that IONOLAB-BIAS is in excellent accordance with the sparse estimates from the IGS centers for all ionospheric states and regions IONOLAB-BIAS has a high potential to be an alternative receiver bias computation algorithm with its ease of implementation and accurate estimates for any single station GPS-TEC

191 citations

Journal ArticleDOI
TL;DR: In this article, a 3D, time-dependent algorithm is presented for imaging ionospheric electron concentration using GPS signals, which results in a three-dimensional movie rather than a static image of the electron-concentration distribution.
Abstract: Global Positioning System (GPS) satellite receivers provide a world-wide network of phase and group delay measurements. The combination of two-frequency measurements can be used to derive the integral of the electron concentration along each satellite-to-receiver path, a parameter known as the Total Electron Content (TEC). At this stage these slant TEC data are diffi cult to interpret as they originate from a combination of a temporally changing ionosphere and spatially changing observation geometry. In this paper TEC data are inverted to evaluate the underlying distribution and time evolution of electron concentration. Accordingly, a new three-dimensional, time-dependent algorithm is presented here for imaging ionospheric electron concentration using GPS signals. The inversion results in a three-dimensional movie rather than a static image of the electron-concentration distribution. The technique is demonstrated using simulated ground-based GPS data from actual measurement geometry over Europe.

184 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the opportunities to use the Global Positioning System (GPS) for ionospheric total electron content (TEC) research and showed that with appropriate smoothing, GPS TECs can be used to extend the existing database.
Abstract: Opportunities to use the Global Positioning System (GPS) for ionospheric total electron content (TEC) research are reviewed. The era of TEC measurements using very high frequency geosynchronous beacons is essentially over, and the new GPS TECs need to be treated in special ways if they are to augment the existing database of total electron content. Data taken at Boulder, Colorado, show that with appropriate smoothing, GPS TECs can be used to extend the existing database. The time delay data from the International GPS Geodynamics Service over central Europe are used to map the total electron content and reveal regional structures. Global electron-density profiles can now be measured using the GPS/MET (meteorology) system. The measurement of precipitable water vapor in the troposphere to an accuracy of 10% requires that 99.9% of the ionospheric delay be removed.

175 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022578
2021284
2020321
2019293
2018272